Antibiotics: Tips for Safe Use
A Primer on the Proper Use of Antibiotics
Aug. 8, 2007—
In the time since penicillin was discovered nearly 80 years ago, antibiotics have become one of the most important lifesaving weapons in doctors' arsenal against bacterial infection.
Now, the Lakeland, Fla.-based Publix grocery store chain is giving away seven of these drugs free of charge to those who have prescriptions for them.
Five of these -- amoxicillin, ampicillin, cephalexin, erythromycin and penicillin VK -- are commonly used by doctors to treat bacterial infections ranging from ear infections to gonorrhea.
But two of the drugs on the list -- ciprofloxacin and sulfamethoxazole/trimethoprim -- are high-grade antibiotics that doctors usually reserve for particularly serious infections.
While some hail the program as a godsend, others fear that the move could lead to overuse of the drugs.
This is because the use of antibiotics comes attached with important considerations. According to the American Academy of Family Physicians, there are certain situations in which antibiotics are helpful -- and many in which they can cause more harm than good.
Here are just a few tips that consumers can use to keep themselves safe when it comes to antibiotics:
Skip the antibiotics for the flu and the common cold. Antibiotics do not work against all infections. By their very nature, they are effective against only those caused by bacteria. This means that if you are suffering from a viral infection like the common cold or seasonal flu, they will likely do nothing to improve your health.
Never take antibiotics that have not been prescribed to you by a doctor. Taking these drugs inappropriately may not only bring no benefit but may also increase the chances that harmful bacteria present in your body could develop resistance to the drugs. The more resistant a bacteria is to treatment, the more dangerous it becomes.
Always finish the entire course of antibiotics you receive. Even if you start to feel better in the middle of the course of treatment, you must finish every pill that has been prescribed to you by a doctor. Failing to do so could increase the chances of developing bacterial resistance.
Keep careful track of any adverse reactions you experience when taking antibiotics. Many people experience adverse effects when taking certain antibiotics, whether they're allergic reactions or something else. It is important to make a note of these reactions so you can inform your doctor and lessen your chances of receiving the same drug again.
Thursday, August 14, 2008
Thursday, August 7, 2008
Vitamin B 6 deficiency
Vitamin B6 deficiency
Definition
Vitamin B6 is used by the body as a catalyst in reactions that involve amino acids. Vitamin B6 deficiency is rare, since most foods eaten contain the vitamin.
Description
Vitamin B6 is a water-soluble vitamin. The recommended dietary allowance (RDA) for vitamin B6 is 2.0 mg/day for the adult man and 1.6 mg/day for the adult woman. Vitamin B6 in the diet generally occurs as a form called pyridoxal phosphate. In this form, it cannot be absorbed by the body. During the process of digestion, the phosphate group is removed, and pyridoxal is produced. However, the body readily absorbs pyridoxal, and converts it back to the active form of the vitamin (pyridoxal phosphate).
Poultry, fish, liver, and eggs are good sources of vitamin B6, comprising about 3-4 mg vitamin/kg food; meat and milk contain lesser amounts of the vitamin. The vitamin also occurs, at about half this level, in a variety of plant foods, including beans, broccoli, cabbage, and peas. Vitamin B6 tends to be destroyed with prolonged cooking, with storage, or with exposure to light.
As mentioned, vitamin B6 takes various forms. One of these forms, called pyridoxine, is relatively stable. For this reason, pyridoxine is the form of vitamin B6 that is used in vitamin supplements, or when foods are fortified. Apples and other fruits are poor sources of the vitamin, containing only 0.2-0.6 mg vitamin/kg food.
Vitamin B6, used mainly in the body for the processing of amino acids, performs this task along with certain enzymes. The enzyme that participates in this type of complex is aminotransferase. Several types of aminotransferase exist. With vitamin B6 deficiency, while aminotransferase continues to occur in the various organs of the body, there is an abnormally low level of the active vitamin B6/aminotransferase complex present. Thus, this vitamin deficiency results in the impairment of a variety of activities in the body. With supplement correction of the vitamin B6 deficiency, the aminotransferase then readily forms the active complex, and normal metabolism is restored.
Vitamin B6 converts certain amino acids (glutamic acid, aspartic acid, glycine) to energy. This allows the body to process all dietary protein, even when the dietary protein is in excess of the body's needs. Vitamin B6 also allows the body to synthesize certain amino acids. For example, if the diet is deficient or low in certain amino acids, such as glycine or serine, vitamin B6 enables the body to make them from sugar. Vitamin B6 is used also for the synthesis of certain hormones, such as adrenaline.
Causes and symptoms
Vitamin B6 deficiency occurs rarely. When it does, it is usually associated with poor absorption of nutrients in the gastrointestinal tract (as in alcoholism, or with chronic diarrhea), the taking of certain drugs (as isoniazid, hydrolazine, penicillamine) that inactivate the vitamin, with genetic disorders that inhibit metabolism of the vitamin, or in cases of starvation.
The symptoms of vitamin B6 deficiency in adults are only vaguely defined. These include nervousness, irritability, insomnia, muscle weakness, and difficulty in walking. Vitamin B6 deficiency may produce fissures and cracking at the corners of the mouth. The deficiency occurred in infants fed early versions of commercial canned infant formula, when the vitamin had been inadvertently omitted from the formula. This error resulted in infants failing to grow, in irritability, and in seizures.
Diagnosis
Vitamin B6 status is measured by the transaminase stimulation test. This test requires extraction of red blood cells, and placement of the cells in two test tubes. Special chemicals (reagents) are added to both test tubes to allow for measurement of aminotransferase. This enzyme requires pyridoxal phosphate. A known quantity of pure pyridoxal phosphate is added to one of the test tubes. The activity level of the enzyme is measured, and compared, in both test tubes. If the added pyridoxal phosphate did not stimulate activity, the patient is considered not to be deficient in vitamin B6. Neither is the patient considered deficient if only slight stimulation occurred. But if a stimulation of four-fold or more occurred, a vitamin B6 deficiency is present.
Treatment
Vitamin B6 deficiency can be prevented or treated with consumption of the recommended dietary allowance, as supplied by food or by vitamin supplements.
Prognosis
The prognosis for correcting vitamin B6 deficiency is excellent.
Prevention
Vitamin B6 deficiency is not a major concern for most people. The deficiency can be prevented with consumption of a mixed diet that includes poultry, fish, eggs, meat, vegetables, and grains.
Key Terms
Amino acid
Amino acids are small molecules that are used as building blocks for all proteins. Some amino acids are also used in the body for the manufacture of hormones. There are about 20 nutritionally important amino acids, including glutamic acid, glycine, methionine, lysine, tryptophan, serine, and glycine.
Fat-soluble vitamins
Fat-soluble vitamins can be dissolved in oil or in melted fat.
Recommended Dietary Allowance (RDA)
The Recommended Dietary Allowances (RDAs) are quantities of nutrients in the diet that are required to maintain good health in people. RDAs are established by the Food and Nutrition Board of the National Academy of Sciences, and may be revised every few years. A separate RDA value exists for each nutrient. The RDA values refer to the amount of nutrient expected to maintain good health in people. The actual amounts of each nutrient required to maintain good health in specific individuals differ from person to person.
Water-soluble vitamins
Water-soluble vitamins can be dissolved in water or juice.
For Your Information
Resources
Books
Brody, T. Nutritional Biochemistry. San Diego: Academic Press, Inc., 1998.
Definition
Vitamin B6 is used by the body as a catalyst in reactions that involve amino acids. Vitamin B6 deficiency is rare, since most foods eaten contain the vitamin.
Description
Vitamin B6 is a water-soluble vitamin. The recommended dietary allowance (RDA) for vitamin B6 is 2.0 mg/day for the adult man and 1.6 mg/day for the adult woman. Vitamin B6 in the diet generally occurs as a form called pyridoxal phosphate. In this form, it cannot be absorbed by the body. During the process of digestion, the phosphate group is removed, and pyridoxal is produced. However, the body readily absorbs pyridoxal, and converts it back to the active form of the vitamin (pyridoxal phosphate).
Poultry, fish, liver, and eggs are good sources of vitamin B6, comprising about 3-4 mg vitamin/kg food; meat and milk contain lesser amounts of the vitamin. The vitamin also occurs, at about half this level, in a variety of plant foods, including beans, broccoli, cabbage, and peas. Vitamin B6 tends to be destroyed with prolonged cooking, with storage, or with exposure to light.
As mentioned, vitamin B6 takes various forms. One of these forms, called pyridoxine, is relatively stable. For this reason, pyridoxine is the form of vitamin B6 that is used in vitamin supplements, or when foods are fortified. Apples and other fruits are poor sources of the vitamin, containing only 0.2-0.6 mg vitamin/kg food.
Vitamin B6, used mainly in the body for the processing of amino acids, performs this task along with certain enzymes. The enzyme that participates in this type of complex is aminotransferase. Several types of aminotransferase exist. With vitamin B6 deficiency, while aminotransferase continues to occur in the various organs of the body, there is an abnormally low level of the active vitamin B6/aminotransferase complex present. Thus, this vitamin deficiency results in the impairment of a variety of activities in the body. With supplement correction of the vitamin B6 deficiency, the aminotransferase then readily forms the active complex, and normal metabolism is restored.
Vitamin B6 converts certain amino acids (glutamic acid, aspartic acid, glycine) to energy. This allows the body to process all dietary protein, even when the dietary protein is in excess of the body's needs. Vitamin B6 also allows the body to synthesize certain amino acids. For example, if the diet is deficient or low in certain amino acids, such as glycine or serine, vitamin B6 enables the body to make them from sugar. Vitamin B6 is used also for the synthesis of certain hormones, such as adrenaline.
Causes and symptoms
Vitamin B6 deficiency occurs rarely. When it does, it is usually associated with poor absorption of nutrients in the gastrointestinal tract (as in alcoholism, or with chronic diarrhea), the taking of certain drugs (as isoniazid, hydrolazine, penicillamine) that inactivate the vitamin, with genetic disorders that inhibit metabolism of the vitamin, or in cases of starvation.
The symptoms of vitamin B6 deficiency in adults are only vaguely defined. These include nervousness, irritability, insomnia, muscle weakness, and difficulty in walking. Vitamin B6 deficiency may produce fissures and cracking at the corners of the mouth. The deficiency occurred in infants fed early versions of commercial canned infant formula, when the vitamin had been inadvertently omitted from the formula. This error resulted in infants failing to grow, in irritability, and in seizures.
Diagnosis
Vitamin B6 status is measured by the transaminase stimulation test. This test requires extraction of red blood cells, and placement of the cells in two test tubes. Special chemicals (reagents) are added to both test tubes to allow for measurement of aminotransferase. This enzyme requires pyridoxal phosphate. A known quantity of pure pyridoxal phosphate is added to one of the test tubes. The activity level of the enzyme is measured, and compared, in both test tubes. If the added pyridoxal phosphate did not stimulate activity, the patient is considered not to be deficient in vitamin B6. Neither is the patient considered deficient if only slight stimulation occurred. But if a stimulation of four-fold or more occurred, a vitamin B6 deficiency is present.
Treatment
Vitamin B6 deficiency can be prevented or treated with consumption of the recommended dietary allowance, as supplied by food or by vitamin supplements.
Prognosis
The prognosis for correcting vitamin B6 deficiency is excellent.
Prevention
Vitamin B6 deficiency is not a major concern for most people. The deficiency can be prevented with consumption of a mixed diet that includes poultry, fish, eggs, meat, vegetables, and grains.
Key Terms
Amino acid
Amino acids are small molecules that are used as building blocks for all proteins. Some amino acids are also used in the body for the manufacture of hormones. There are about 20 nutritionally important amino acids, including glutamic acid, glycine, methionine, lysine, tryptophan, serine, and glycine.
Fat-soluble vitamins
Fat-soluble vitamins can be dissolved in oil or in melted fat.
Recommended Dietary Allowance (RDA)
The Recommended Dietary Allowances (RDAs) are quantities of nutrients in the diet that are required to maintain good health in people. RDAs are established by the Food and Nutrition Board of the National Academy of Sciences, and may be revised every few years. A separate RDA value exists for each nutrient. The RDA values refer to the amount of nutrient expected to maintain good health in people. The actual amounts of each nutrient required to maintain good health in specific individuals differ from person to person.
Water-soluble vitamins
Water-soluble vitamins can be dissolved in water or juice.
For Your Information
Resources
Books
Brody, T. Nutritional Biochemistry. San Diego: Academic Press, Inc., 1998.
Sunday, August 3, 2008
Comparison of Iron Supplements
Comparison of Oral Iron Supplements
A new iron supplement product in the U.S. called Ferralet 90 is adding to the confusion surrounding the numerous oral iron supplements on the market. Ferralet 90 is a combination product containing carbonyl iron, B12, vitamin C, folic acid, and docusate and it is marketed as a prescription product. No oral iron dietary supplements are approved by the FDA, but manufacturers can choose to market their products as prescription only.8 There are two main iron salts forms (ferric and ferrous irons) and numerous formulations (e.g., amino-acid chelates, carbonyl iron, polysaccharide-iron complex, combination products, extended-release products, etc) available in the U.S. and Canada. All dietary iron has to be reduced to the ferrous form to enter the mucosal cells; therefore ferrous iron is absorbed three times more readily than the ferric form. Anecdotal claims that sustained-release iron preparations cause fewer gastrointestinal side effects have not been well substantiated.1,2 There is some evidence that controlled-release iron preparation causes less nausea and epigastric pain than conventional ferrous sulfate, but the discontinuation rates are similar.3 Theoretically, once-daily dosing can improve compliance. However, extended-release or enteric-coated formulations have been found to transport iron past the duodenum and proximal jejunum, thereby reducing the absorption of iron.1,2 Vitamin C is added to some products to enhance iron absorption. About 200 mg is needed to increase absorption of 30 mg of elemental iron.1 However, doses of 500 mg to 1000 mg only increase iron absorption by about 10%.2 Most iron preparations containing vitamin C don't have a sufficient amount of vitamin C to substantially affect iron absorption.1,2 In general, iron supplements should be taken on an empty stomach since food can decrease absorption by 40% to 50%. GI side effects such as nausea and abdominal pain occur more frequently as the quantity of soluble elemental iron in contact with the stomach and duodenum increases. Higher iron doses also increase the occurrence of constipation.1,10 Therefore, there should be no difference in GI tolerance when an equal quantity of elemental iron is administered regardless of the form of iron salt.2 A chart summarizing the differences among the various iron formulations is included.
There's confusion about the different oral iron products.
Many are promoted as better tolerated or absorbed...but not all of these claims can be substantiated.
Ferrous sulfate, ferrous gluconate, and ferrous fumarate contain different percentages of elemental iron. Efficacy and tolerability are similar for equal doses of elemental iron.
Carbonyl iron (Ferralet 90, Feosol Carbonyl Iron caplets, etc) is pure elemental iron that's absorbed slowly to reduce toxicity.
Prescribe these if you're concerned about accidental ingestion. Iron is still the #1 cause of pediatric fatalities due to toxicity.
Polysaccharide-iron complex (Niferex-150, etc) is iron bound to carbohydrates. It's promoted to improve tolerability, but there's no proof that there's a significant difference.
Heme iron polypeptide (Proferrin ES, etc) is derived from hemoglobin in animal red blood cells. It's better absorbed than the inorganic iron salts, especially when taken with food.
Use the inexpensive ferrous sulfate first-line...or carbonyl iron if toxicity is a concern.
Tell patients that GI tolerability is linked to the iron DOSE...not the salt. Enteric-coated and controlled-release preps might reduce nausea...but at the expense of lower absorption.
Vitamin C increases iron absorption, but most combo products don't contain enough. Over 200 mg is needed to increase absorption of 30 mg elemental iron.
A new iron supplement product in the U.S. called Ferralet 90 is adding to the confusion surrounding the numerous oral iron supplements on the market. Ferralet 90 is a combination product containing carbonyl iron, B12, vitamin C, folic acid, and docusate and it is marketed as a prescription product. No oral iron dietary supplements are approved by the FDA, but manufacturers can choose to market their products as prescription only.8 There are two main iron salts forms (ferric and ferrous irons) and numerous formulations (e.g., amino-acid chelates, carbonyl iron, polysaccharide-iron complex, combination products, extended-release products, etc) available in the U.S. and Canada. All dietary iron has to be reduced to the ferrous form to enter the mucosal cells; therefore ferrous iron is absorbed three times more readily than the ferric form. Anecdotal claims that sustained-release iron preparations cause fewer gastrointestinal side effects have not been well substantiated.1,2 There is some evidence that controlled-release iron preparation causes less nausea and epigastric pain than conventional ferrous sulfate, but the discontinuation rates are similar.3 Theoretically, once-daily dosing can improve compliance. However, extended-release or enteric-coated formulations have been found to transport iron past the duodenum and proximal jejunum, thereby reducing the absorption of iron.1,2 Vitamin C is added to some products to enhance iron absorption. About 200 mg is needed to increase absorption of 30 mg of elemental iron.1 However, doses of 500 mg to 1000 mg only increase iron absorption by about 10%.2 Most iron preparations containing vitamin C don't have a sufficient amount of vitamin C to substantially affect iron absorption.1,2 In general, iron supplements should be taken on an empty stomach since food can decrease absorption by 40% to 50%. GI side effects such as nausea and abdominal pain occur more frequently as the quantity of soluble elemental iron in contact with the stomach and duodenum increases. Higher iron doses also increase the occurrence of constipation.1,10 Therefore, there should be no difference in GI tolerance when an equal quantity of elemental iron is administered regardless of the form of iron salt.2 A chart summarizing the differences among the various iron formulations is included.
There's confusion about the different oral iron products.
Many are promoted as better tolerated or absorbed...but not all of these claims can be substantiated.
Ferrous sulfate, ferrous gluconate, and ferrous fumarate contain different percentages of elemental iron. Efficacy and tolerability are similar for equal doses of elemental iron.
Carbonyl iron (Ferralet 90, Feosol Carbonyl Iron caplets, etc) is pure elemental iron that's absorbed slowly to reduce toxicity.
Prescribe these if you're concerned about accidental ingestion. Iron is still the #1 cause of pediatric fatalities due to toxicity.
Polysaccharide-iron complex (Niferex-150, etc) is iron bound to carbohydrates. It's promoted to improve tolerability, but there's no proof that there's a significant difference.
Heme iron polypeptide (Proferrin ES, etc) is derived from hemoglobin in animal red blood cells. It's better absorbed than the inorganic iron salts, especially when taken with food.
Use the inexpensive ferrous sulfate first-line...or carbonyl iron if toxicity is a concern.
Tell patients that GI tolerability is linked to the iron DOSE...not the salt. Enteric-coated and controlled-release preps might reduce nausea...but at the expense of lower absorption.
Vitamin C increases iron absorption, but most combo products don't contain enough. Over 200 mg is needed to increase absorption of 30 mg elemental iron.
Sunday, July 27, 2008
Iron absorption
Iron Absorption 7/27/08 1:23 PM
Overview
Despite the fact that iron is the second most abundant metal in the earth's crust, iron
deficiency is the world's most common cause of anemia. When it comes to life, iron is more precious than
gold. The body hoards the element so effectively that over millions of years of evolution, humans have
developed no physiological means of iron excretion. Iron absorption is the sole mechanism by which iron
stores are physiologically manipulated.
The average adult stores about 1 to 3 grams of iron in his or her body. An exquisite balance between dietary
uptake and loss maintains this balance. About 1 mg of iron is lost each day through sloughing of cells from
skin and mucosal surfaces, including the lining of the gastrointestinal tract (Cook et al., 1986). Menstration
increases the average daily iron loss to about 2 mg per day in premenopausal female adults (Bothwell and
Charlton, 1982). No physiologic mechanism of iron excretion exists. Consequently, absorption alone
regulates body iron stores (McCance and Widdowson, 1938). The augmentation of body mass during
neonatal and childhood growth spurts transiently boosts iron requirements (Gibson et al., 1988).
Iron Absorption
Iron absorption occurs predominantly in the duodenum and
upper jejunum ( Muir and Hopfer, 1985) (Figure 1). The
mechanism of iron transport from the gut into the blood
stream remains a mystery despite intensive investigation
and a few tantalizing hits (see below). A feedback
mechanism exists that enhances iron absorption in people
who are iron deficient. In contrast, people with iron
overload dampen iron absorption.
The physical state of iron entering the duodenum greatly
influences its absorption however. At physiological pH,
ferrous iron (Fe2+) is rapidly oxidized to the insoluble ferric
(Fe3+) form. Gastric acid lowers the pH in the proximal
duodenum, enhancing the solubility and uptake of ferric
iron (Table 1). When gastric acid production is impaired
(for instance by acid pump inhibitors such as the drug,
prilosec), iron absorption is reduced substantially.
Heme is absorbed by machinery completely different to that
of inorganic iron. The process is more efficient and is
independent of duodenal pH . Consequently meats are
excellent nutrient sources of iron. In fact, blockade of heme
catabolism in the intestine by a heme oxygenase inhibitor
The iron is coupled to transferrin (Tf) in the
circulation which delivers it to the cells of the
body. Phytates, tannins and antacids block
iron absorption.
Table 1. Factors That Influence Iron Absorption
Physical State (bioavailability) heme > Fe2+ > Fe3+
Inhibitors phytates, tannins, soil clay, laundry starch, iron overload, antacids
Competitors lead, cobalt, strontium, manganese, zinc
Facilitators ascorbate, citrate, amino acids, iron deficiency
can produce iron deficiency (Kappas et al., 1993). The
paucity of meats in the diets of many of the people in the
world adds to the burden of iron deficiency.
A number of dietary factors influence iron absorption. Ascorbate and citrate increase iron uptake in part by
acting as weak chelators to help to solubilize the metal in the duodenum (Table 1) (Conrad and Umbreit,
1993). Iron is readily transferred from these compounds into the mucosal lining cells. Conversely, iron
absorption is inhibited by plant phytates and tannins. These compounds also chelate iron, but prevent its
uptake by the absorption machinery (see below). Phytates are prominent in wheat and some other cereals,
while tannins are prevalent in (non-herbal) teas.
Lead is a particularly pernicious element to iron metabolism (Goya, 1993). Lead is taken up by the iron
absorption machinery, and secondarily blocks iron through competitive inhibition. Further, lead interferes
with a number of important iron-dependent metabolic steps such as heme biosynthesis. This multifacted
attack has particularly dire consequences in children, were lead not only produces anemia, but can impair
cognitive development. Lead exists naturally at high levels in ground water and soil in some regions, and
can clandestinely attack children's health. For this reason, most pediatricians in the U.S. routinely test for
lead at an early age through a simple blood test.
Immaturity of the gastrointestinal tract can exacerbate iron deficiency in newborns. The gastrointestinal tract
does not achieve competency for iron absorption for several weeks after birth. The problem is even more
severe for premature infants, who tend to be anemic for a variety of reasons. A substantial portion of iron
stores in newborns are transferred from the mother late in pregnancy. Prematurity shortcircuits this process.
Parenteral iron replacement is possible, but not often used because of the often delicate health of premature
infants. Transfusion becomes the default option in this circumstance.
The mechanism by which iron enters the mucosal cells lining the upper gastrointestinal tract is unknown. Most
cells in the rest of the body are believed to acquire iron from plasma transferrin (an iron-protein chelate),
via specific transferrin receptors and receptor-mediated endocytosis (Klausner, et al, 1983). The hypothesis
that apotransferrin (or an equivalent molecule) secreted by intestinal cells or present in bile chelates
intestinal iron and facilitates its absorption(Huebers et al., 1983) is unsubstantiated. The transferrin gene is
not expressed in intestinal cells. Later work indicated that transferrin found in the intestinal lumen is derived
from plasma (Idzerda et al., 1986). Plasma transferrin entering bile is fully saturated with iron, obviating
any intraluminal chelating function (Schumann et al., 1986). Furthermore, hypoxia, which greatly increases
iron absorption, has no effect on intestinal transferrin levels (Simpson et al., 1986). Exogenous transferrin
cannot donate iron to intestinal mucosal cells (Bezwoda et al., 1986), and the brush boarder membrance
lacks transferrin receptors (Parmley et al., 1985) (although they are present on the basolateral surface of
intestinal epithelial cells (Levin et al., 1984); (Banerjee et al., 1986). Lastly and perhaps most compellingly,
humans and mice with hypotransferrinemia paradoxically absorb more dietary iron than normal. Although
the erythron is iron deficient, these individuals develop hepatic iron overload (Heilmeyer et al., 1961);
(Craven et al., 1987).
Mechanism of Iron Absorption
In searching for molecules involved in intestinal iron transport, Conrad and co-workers took the approach of
characterizing proteins that bind iron [summarized in (Conrad and Umbreit, 1993)]. Their hypothesis of iron
transport is based on identification of iron binding proteins at several key sites. They propose that mucins
bind iron in the acid environment of the stomach, thereby maintaining it in solution for later uptake in the
alkaline duodenum. According to their model, mucin-bound iron subsequently crosses the mucosal cell
membrane in association with integrins. Once inside the cell, a cytoplasmic iron-binding protein, dubbed
"mobilferrin", accepts the element, and shuttles it to the basolateral surface of the cell, where it is delivered
to plasma. In this model mobilferrin could serve as a rheostat sensitive to plasma iron concentrations. Fully
occupied mobilferrin would dampen mucosal iron uptake, and while the process would be enhanced by
unsaturated mobilferrin (Conrad and Umbreit, 1993). This model has not gained universal acceptance
however.
A very different scheme of iron uptake has been proposed by investigators studying iron transport in yeast.
Yeast face the problem of taking in iron from the environment, a process similar to that of intestinal
mucosal cells. Dancis et al. used genetic selection to isolate Sacchromyces cerevisiae mutants with defective
iron transport (Dancis et al., 1994); (Stearman et al., 1996). They constructed an expression plasmid in
which an enzyme necessary for histidine biosynthesis was under the control of an iron-repressible promoter.
The plasmid was introduced into a yeast histidine auxotroph (i.e. a strain of yeast that requires histidine to
survive). Mutants were selected in the absence of histidine, in the presence of high levels of iron. Among
the mutats they isolated, were cells with defective iron uptake. They discovered that membrane iron
transport depends absolutely upon copper transport. In this model, ferric iron in yeast culture medium is
reduced to its ferrous form by an externally oriented reductase (FRE1). The element is shuttled rapidly into
the cell by a ferrous transporter, which appears to be coupled to an externally oriented copper-dependent
oxidase (FET3) embedded in the cell membrane (De Silva et al., 1995); (Stearman et al., 1996). FET3 is
strikingly homologous to the mammalian copper oxidase ceruloplasmin. The re-oxidation of ferrous to ferric
iron is apparently an obligatory step in the transport mechanism, although the coupling mechanism of
oxidation and membrane transport is unclear. (De Silva et al., 1995); (Stearman et al., 1996); (Yuan et al.,
1995). Although the genetic evidence for this scheme is compelling, the central component, the ferrous
transporter itself, remains elusive. These investigators speculate that mammalian intestinal iron transport is
analogous to the yeast iron uptake process (Harford et al., 1994). This assertion is supported by studies of
copper-deficient swine, which show co-existing iron deficiency unresponsive to iron therapy (Lahey et al.,
1952); (Gubler et al., 1952); (Cartwright et al., 1956).
Genetic Insights into Mammalian Iron Absorption
Mouse genetics provides a different perspective on mammalian intestinal iron transport. Mouse breeders
readily recognize pale animals, and have developed anemic stocks with various mutations. Intestinal
mucosal iron transport is defective in two mutant strains. Microcytic (mk) mice and sex-linked anemia (sla)
mice have severe iron deficiency due apparently to defects in iron uptake and release, respectively, from the
intestinal cell (reviewed in [Bannerman, 1976].) Mice with the homozygous autosomal recessive mk
mutation absorb iron poorly, have low serum iron levels, and lack stainable iron in intestinal mucosal cells.
These findings are consistent with a defect in an apical iron transport molecule. Intriguingly, mk/mk mice
Iron Absorption 7/27/08 1:23 PM
http://sickle.bwh.harvard.edu/iron_absorption.html Page 4 of 6
are not rescued by parenteral iron replacement. Anemia develops in normal mice tranplanted with mk bone
marrow, indicating that mk erythroid precursor cells also have a defect in red cell iron uptake. A common
component to iron transport may therefore exist in intestinal cells and red cell precursors (Andrews, et al,
2000).
ÝMice that are homozygous or heterozygous for the sla mutation (sla/sla or sla/y) also have low serum iron
levels. In contrast to mk mice, they have abnormal iron deposits within intestinal mucosal cells, suggesting
that this X-linked defect impairs intracellular iron trafficking or basolateral export of iron to the plasma. The
sla animals differ further from the mk mice by correction of anemia by parenteral iron. Based on studies of
these mutants, distinct apical and basolateral iron transport systems possibly exist that function coordinately
to transfer iron from intestinal lumen to plasma.
ÝWhatever the mechanism of iron uptake, normally only about 10% of the elemental iron entering the
duodenum is absorbed. However, this value increases markedly with iron deficiency (Finch, 1994). In
contrast, iron overload reduces but does not eliminate absorption, reaffirming the fact that absorption is
regulated by body iron stores. In addition, both anemia and hypoxia boost iron absorption. A portion of the
iron that enters the mucosal cells is retained sequestered within ferritin. Intracellular intestinal iron is lost
when epithelial cells are sloughed from the lining of the gastrointestinal tract. The remaining iron traverses
the mucosal cells, to be coupled to transferrin for transport through the circulation.
Erythropoiesis and Iron Absorption
ÝApproximately 80% of total body iron is ultimately incorporated into red cell hemoglobin. An average
adult produces 2 x 1011 red cells daily, for a red cell renewal rate of 0.8 percent per day. Each red cell
contains more than a billion atoms of iron, and each ml of red cells contains 1 mg of iron. To meet this
daily need for 2 x 1020 atoms (or 20 mg) of elemental iron, the body has developed regulatory mechanisms
whereby erythropoiesis profoundly influences iron absorption. Plasma iron turnover (PIT) represents the
mass turnover of transferrin-bound iron in the circulation, expressed as mg/kg/day (Huff et al., 1950).
Accelerated erythropoiesis increases plasma iron turnover, which is associated with enhanced iron uptake
from the gastrointestinal tract (Weintraub et al., 1965). The mechanism by which PIT alters iron absorption
is unknown.
ÝA circulating factor related to erythropoiesis that modulates iron absorption has been hypothesized, but not
identified (Beutler and Buttenweiser, 1960); (Finch, 1994). Several candidate factors have been excluded,
including transferrin (Aron et al., 1985) and erythropoietin (Raja et al., 1986). Clinical manifestations of this
apparent communication between the marrow and the intestine includes iron overload that develops in
patients with severe thalassemia in the absence of transfusion. The accelerated (but ineffective)
erythropoiesis in this condition substantially boosts iron absorption. In some cases, the coupling of increased
PIT and increased gastrointestinal iron absorption is beneficial. In pregnancy, placental removal of iron
raises the PIT. This process enhances gastrointestinal iron absorption thereby increasing the availability of
the element to meet the needs of the growing and developing fetus.
ÝCompetition studies suggest that several other heavy metals share the iron intestinal absorption pathway.
These include lead, manganese, cobalt and zinc (Table 1). Enhanced iron absorption induced by iron
deficiency also augments the uptake of these elements. As iron deficiency often coexists with lead
intoxication, this interaction can produce particularly serious medical complications in children (Piomelli et
al., 1987). Interestingly, copper absorption and metabolism appear to be handled mechanisms different to
those of iron.
References:
Andrews NC. (2000). Intestinal iron absorption: current concepts circa 2000. Dig Liver Dis Jan-
Feb;32(1):56-61.
Banerjee, D., Flanagan, P. R., Cluett, J., and Valberg, L. S. (1986). Transferrin receptors in the human
gastrointestinal tract. Relationship to body iron stores. Gastroenterology 91, 861.
Bannerman, R. M. (1976). Genetic defects of iron transport. Federation Proceedings 35, 2281.
Beutler, E., and Buttenweiser, E. (1960). The regulation of iron absorption. I. A search for humoral
factors. Journal of Laboratory and Clinical Medicine 55, 274.
Bezwoda, W. R., MacPhail, A. P., Bothwell, T. H., Baynes, R. D., Derman, D. P., and Torrance, J. D.
(1986). Failure of transferrin to enhance iron absorption in achlorhydric human subjects. Br. J.
Haematol. 63, 749.
Bothwell, T. H., and Charlton, R. W. (1982). A general approach of the problems of iron deficiency
and iron overload in the population at large. Seminars in Hematology 19, 54.
Cartwright, G. E., Gubler, C. J., Bush, J. A., and Wintrobe, M. M. (1956). Studies on copper
metabolism. XVII. Further observations on the anemia of copper deficiency in swine. Blood 11, 143.
Conrad, M. E., and Umbreit, J. N. (1993). A concise review: Iron absorption - the mucin-mobilferrinintegrin
pathway. A competitive pathway for metal absorption. American Journal of Hematology 42,
67.
Cook, J. D., Skikne, B. S., and al., e. (1986). Estimates of iron sufficiency in the US population.
Blood 68, 726.
Craven, C. M., Alexander, J., Eldridge, M., Kushner, J. P., Bernstein, S., and Kaplan, J. (1987).
Tissue distribution and clearance kinetics of non-transferrin-bound iron in the hypotransferrinemic
mouse: a rodent model for hemochromatosis. Proceedings of the National Academy of Sciences
(USA) 84, 3457.
Dancis, A., Haile, D., Yuan, D.S., Klausner, R.D. (1994). The Saccharomyces cerevisiae copper
transport protein (Ctr1p). Biochemical characterization, regulation by copper, and physiologic role in
copper uptake. J. Biol. Chem. 269, 25660-7
De Silva, D. M., Askwith, C. C., Eide, D., and Kaplan, J. (1995). The FET3 gene product required for
high affinity iron transport in yeast is a cell surface ferroxidase. Journal of Biological Chemistry 270,
1098-101.
Finch, C. (1994). Regulators of iron balance in humans. Blood 84, 1697.
Gibson, R. S., MacDonald, A. C., and Smit-Vanderkooy, P. D. (1988). Serum ferritin and dietary iron
parameters in a sample of Canadian preschool children. J. Can. Dietetic Assoc. 49, 23.
Goyer, RA. (1993) Lead toxicity: current concerns. Environ Health Perspect 100: 177-187.
Gubler, C. J., Lahey, M. E., Chase, M. S., Cartwright, G. E., and Wintrobe, M. M. (1952). Studies on
copper metabolism. III. The metabolism of iron in copper deficient swine. Blood 7, 1075.
Harford, J. B., Rouault, T. A., Huebers, H. A., and Klausner, R. D. (1994). Molecular mechanisms of
iron metabolism. In The Molecular Basis of Blood Diseases, G. Stamatoyannopoulos, A. W. Nienhuis,
P. W. Majerus and H. Varmus, eds. (Philadelphia: W.B. Saunders Co.), pp. 351-378.
Heilmeyer, L., Keller, W., Vivell, O. Keiderling, W., Betke, K., Wohler, F., Schultze, H.E. (1961)
Congenital transferrin deficiency in a seven-year old girl. German Medical Monthly 6, 385
Iron Absorption 7/27/08 1:23 PM
http://sickle.bwh.harvard.edu/iron_absorption.html Page 6 of 6
Huebers, H. A., Huebers, E., and al., e. (1983). The significance of transferrin for intestinal iron
absorption. Blood 61, 283.
Huff, R. L., Hennessey, T. G., Austin, R. E., Garcia, J. F., Roberts, B. M., and Lawrence, J. H.
(1950). Plasma and red cell iron turnover in normal subjects and in patients having various
hematopoietic disorders. Journal of Clinical Investigation 29, 1041.
Idzerda, R. L., Huebers, H., and al., e. (1986). Rat transferrin gene expression: tissue-specific
regulation by iron deficiency. Proceedings of the National Academy of Sciences (USA) 83, 3723.
Kappas, A., Drummond, G. S., and Galbraith, R. A. (1993). Prolonged clinical use of a heme
oxygenase inhibitor: hematological evidence for an inducible but reversible iron-deficiency state.
Pediatrics 91, 537-539.
Klausner R.D., van Renswoude J., Ashwell G., Kempf, C, Schechter, AN, Dean, A, Bridges, KR.
(1983) Receptor-mediated endocytosis of transferrin in K562 cells. J. Biol. Chem. 258: 4715 - 4724.
Lahey, M. E., Gubler, C. J., Chase, M. S., Cartwright, G. E., and Wintrobe, M. M. (1952). Studies on
copper metabolism. II. Hematologic manifestations of copper deficiency in swine. Blood 7, 1075.
Levin, M. J., Tuil, D., and al., e. (1984). Expression of transferrin gene during development of nonhepatic
tissues: High level of transferrin mRNA in fetal muscle and adult brain. Biochem. Biophys.
Res. Commun. 122, 212.
McCance, R. A., and Widdowson, E. M. (1938). The absorption and excretion of iron following oral
and intravenous administration. J. Phys. 94, 148.
Muir, A., and Hopfer, U. (1985). Regional specificity of iron uptake by smal intestinal brush-boarder
membranes from normal and iron deficient mice. Gastrointestinal and Liver Pathology 11, 6376-6379.
Parmley, R. T., Barton, J. C., and Conrad, M. E. (1985). Ultrastructural localization of transferrin,
transferrin receptor and iron-binding sites on human placental and duodenal microvilli. Br. J.
Haematol. 60, 81.
Piomelli, S., Seaman, C., and Kapoor, S. (1987). Lead-induced abnormalities of porphyrin
metabolism. The relationship with iron deficiency. Ann. NY Acad. Sci. 514, 278.
Raja, K. N., Pippard, M. J., Simpson, R. J., and Peters, T. J. (1986). Relationship between
erythropoiesis and the enhanced intestinal uptake of ferric iron in hypoxia in the mouse. British
Journal of Haematology 64, 587.
Schumann, K., Schafer, S. G., and Forth, W. (1986). Iron absorption and biliary excretion of
transferrin in rats. Res. Exp. Med. 186, 215.
Simpson, R. J., Osterloh, K. R. S., Raja, K. B., Snape, S. D., and Peters, T. J. (1986). Studies on the
role of transferrin and endocytosis on the uptake of Fe3+ from Fe-nitriloacetate by mouse duodenum.
Biochim. Biophys. Acta 884, 166.
Stearman, R., Yuan, D. S., Yamaguchi-Iwai, Y., Klausner, R. D., and Dancis, A. (1996). A permeaseoxidase
complex involved in high-affinity iron uptake in yeast. Science 271, 1552-1557.
Weintraub, L. R., Conrad, M. E., and Crosby, W. H. (1965). Regulation of the intestinal absorption of
iron by the rate of erythropoiesis. British Journal of Hematology 2, 432.
Yuan, D. S., Stearman, R., Dancis, A., Dunn, T., Beeler, T., and Klausner, R. D. (1995). The
Menkes/Wilson disease gene homologue in yeast provides copper to a ceruloplasmin-like oxidase
required for iron uptake. Proceedings of the National Academy of Sciences (USA) 92, 2632-2636.
Overview
Despite the fact that iron is the second most abundant metal in the earth's crust, iron
deficiency is the world's most common cause of anemia. When it comes to life, iron is more precious than
gold. The body hoards the element so effectively that over millions of years of evolution, humans have
developed no physiological means of iron excretion. Iron absorption is the sole mechanism by which iron
stores are physiologically manipulated.
The average adult stores about 1 to 3 grams of iron in his or her body. An exquisite balance between dietary
uptake and loss maintains this balance. About 1 mg of iron is lost each day through sloughing of cells from
skin and mucosal surfaces, including the lining of the gastrointestinal tract (Cook et al., 1986). Menstration
increases the average daily iron loss to about 2 mg per day in premenopausal female adults (Bothwell and
Charlton, 1982). No physiologic mechanism of iron excretion exists. Consequently, absorption alone
regulates body iron stores (McCance and Widdowson, 1938). The augmentation of body mass during
neonatal and childhood growth spurts transiently boosts iron requirements (Gibson et al., 1988).
Iron Absorption
Iron absorption occurs predominantly in the duodenum and
upper jejunum ( Muir and Hopfer, 1985) (Figure 1). The
mechanism of iron transport from the gut into the blood
stream remains a mystery despite intensive investigation
and a few tantalizing hits (see below). A feedback
mechanism exists that enhances iron absorption in people
who are iron deficient. In contrast, people with iron
overload dampen iron absorption.
The physical state of iron entering the duodenum greatly
influences its absorption however. At physiological pH,
ferrous iron (Fe2+) is rapidly oxidized to the insoluble ferric
(Fe3+) form. Gastric acid lowers the pH in the proximal
duodenum, enhancing the solubility and uptake of ferric
iron (Table 1). When gastric acid production is impaired
(for instance by acid pump inhibitors such as the drug,
prilosec), iron absorption is reduced substantially.
Heme is absorbed by machinery completely different to that
of inorganic iron. The process is more efficient and is
independent of duodenal pH . Consequently meats are
excellent nutrient sources of iron. In fact, blockade of heme
catabolism in the intestine by a heme oxygenase inhibitor
The iron is coupled to transferrin (Tf) in the
circulation which delivers it to the cells of the
body. Phytates, tannins and antacids block
iron absorption.
Table 1. Factors That Influence Iron Absorption
Physical State (bioavailability) heme > Fe2+ > Fe3+
Inhibitors phytates, tannins, soil clay, laundry starch, iron overload, antacids
Competitors lead, cobalt, strontium, manganese, zinc
Facilitators ascorbate, citrate, amino acids, iron deficiency
can produce iron deficiency (Kappas et al., 1993). The
paucity of meats in the diets of many of the people in the
world adds to the burden of iron deficiency.
A number of dietary factors influence iron absorption. Ascorbate and citrate increase iron uptake in part by
acting as weak chelators to help to solubilize the metal in the duodenum (Table 1) (Conrad and Umbreit,
1993). Iron is readily transferred from these compounds into the mucosal lining cells. Conversely, iron
absorption is inhibited by plant phytates and tannins. These compounds also chelate iron, but prevent its
uptake by the absorption machinery (see below). Phytates are prominent in wheat and some other cereals,
while tannins are prevalent in (non-herbal) teas.
Lead is a particularly pernicious element to iron metabolism (Goya, 1993). Lead is taken up by the iron
absorption machinery, and secondarily blocks iron through competitive inhibition. Further, lead interferes
with a number of important iron-dependent metabolic steps such as heme biosynthesis. This multifacted
attack has particularly dire consequences in children, were lead not only produces anemia, but can impair
cognitive development. Lead exists naturally at high levels in ground water and soil in some regions, and
can clandestinely attack children's health. For this reason, most pediatricians in the U.S. routinely test for
lead at an early age through a simple blood test.
Immaturity of the gastrointestinal tract can exacerbate iron deficiency in newborns. The gastrointestinal tract
does not achieve competency for iron absorption for several weeks after birth. The problem is even more
severe for premature infants, who tend to be anemic for a variety of reasons. A substantial portion of iron
stores in newborns are transferred from the mother late in pregnancy. Prematurity shortcircuits this process.
Parenteral iron replacement is possible, but not often used because of the often delicate health of premature
infants. Transfusion becomes the default option in this circumstance.
The mechanism by which iron enters the mucosal cells lining the upper gastrointestinal tract is unknown. Most
cells in the rest of the body are believed to acquire iron from plasma transferrin (an iron-protein chelate),
via specific transferrin receptors and receptor-mediated endocytosis (Klausner, et al, 1983). The hypothesis
that apotransferrin (or an equivalent molecule) secreted by intestinal cells or present in bile chelates
intestinal iron and facilitates its absorption(Huebers et al., 1983) is unsubstantiated. The transferrin gene is
not expressed in intestinal cells. Later work indicated that transferrin found in the intestinal lumen is derived
from plasma (Idzerda et al., 1986). Plasma transferrin entering bile is fully saturated with iron, obviating
any intraluminal chelating function (Schumann et al., 1986). Furthermore, hypoxia, which greatly increases
iron absorption, has no effect on intestinal transferrin levels (Simpson et al., 1986). Exogenous transferrin
cannot donate iron to intestinal mucosal cells (Bezwoda et al., 1986), and the brush boarder membrance
lacks transferrin receptors (Parmley et al., 1985) (although they are present on the basolateral surface of
intestinal epithelial cells (Levin et al., 1984); (Banerjee et al., 1986). Lastly and perhaps most compellingly,
humans and mice with hypotransferrinemia paradoxically absorb more dietary iron than normal. Although
the erythron is iron deficient, these individuals develop hepatic iron overload (Heilmeyer et al., 1961);
(Craven et al., 1987).
Mechanism of Iron Absorption
In searching for molecules involved in intestinal iron transport, Conrad and co-workers took the approach of
characterizing proteins that bind iron [summarized in (Conrad and Umbreit, 1993)]. Their hypothesis of iron
transport is based on identification of iron binding proteins at several key sites. They propose that mucins
bind iron in the acid environment of the stomach, thereby maintaining it in solution for later uptake in the
alkaline duodenum. According to their model, mucin-bound iron subsequently crosses the mucosal cell
membrane in association with integrins. Once inside the cell, a cytoplasmic iron-binding protein, dubbed
"mobilferrin", accepts the element, and shuttles it to the basolateral surface of the cell, where it is delivered
to plasma. In this model mobilferrin could serve as a rheostat sensitive to plasma iron concentrations. Fully
occupied mobilferrin would dampen mucosal iron uptake, and while the process would be enhanced by
unsaturated mobilferrin (Conrad and Umbreit, 1993). This model has not gained universal acceptance
however.
A very different scheme of iron uptake has been proposed by investigators studying iron transport in yeast.
Yeast face the problem of taking in iron from the environment, a process similar to that of intestinal
mucosal cells. Dancis et al. used genetic selection to isolate Sacchromyces cerevisiae mutants with defective
iron transport (Dancis et al., 1994); (Stearman et al., 1996). They constructed an expression plasmid in
which an enzyme necessary for histidine biosynthesis was under the control of an iron-repressible promoter.
The plasmid was introduced into a yeast histidine auxotroph (i.e. a strain of yeast that requires histidine to
survive). Mutants were selected in the absence of histidine, in the presence of high levels of iron. Among
the mutats they isolated, were cells with defective iron uptake. They discovered that membrane iron
transport depends absolutely upon copper transport. In this model, ferric iron in yeast culture medium is
reduced to its ferrous form by an externally oriented reductase (FRE1). The element is shuttled rapidly into
the cell by a ferrous transporter, which appears to be coupled to an externally oriented copper-dependent
oxidase (FET3) embedded in the cell membrane (De Silva et al., 1995); (Stearman et al., 1996). FET3 is
strikingly homologous to the mammalian copper oxidase ceruloplasmin. The re-oxidation of ferrous to ferric
iron is apparently an obligatory step in the transport mechanism, although the coupling mechanism of
oxidation and membrane transport is unclear. (De Silva et al., 1995); (Stearman et al., 1996); (Yuan et al.,
1995). Although the genetic evidence for this scheme is compelling, the central component, the ferrous
transporter itself, remains elusive. These investigators speculate that mammalian intestinal iron transport is
analogous to the yeast iron uptake process (Harford et al., 1994). This assertion is supported by studies of
copper-deficient swine, which show co-existing iron deficiency unresponsive to iron therapy (Lahey et al.,
1952); (Gubler et al., 1952); (Cartwright et al., 1956).
Genetic Insights into Mammalian Iron Absorption
Mouse genetics provides a different perspective on mammalian intestinal iron transport. Mouse breeders
readily recognize pale animals, and have developed anemic stocks with various mutations. Intestinal
mucosal iron transport is defective in two mutant strains. Microcytic (mk) mice and sex-linked anemia (sla)
mice have severe iron deficiency due apparently to defects in iron uptake and release, respectively, from the
intestinal cell (reviewed in [Bannerman, 1976].) Mice with the homozygous autosomal recessive mk
mutation absorb iron poorly, have low serum iron levels, and lack stainable iron in intestinal mucosal cells.
These findings are consistent with a defect in an apical iron transport molecule. Intriguingly, mk/mk mice
Iron Absorption 7/27/08 1:23 PM
http://sickle.bwh.harvard.edu/iron_absorption.html Page 4 of 6
are not rescued by parenteral iron replacement. Anemia develops in normal mice tranplanted with mk bone
marrow, indicating that mk erythroid precursor cells also have a defect in red cell iron uptake. A common
component to iron transport may therefore exist in intestinal cells and red cell precursors (Andrews, et al,
2000).
ÝMice that are homozygous or heterozygous for the sla mutation (sla/sla or sla/y) also have low serum iron
levels. In contrast to mk mice, they have abnormal iron deposits within intestinal mucosal cells, suggesting
that this X-linked defect impairs intracellular iron trafficking or basolateral export of iron to the plasma. The
sla animals differ further from the mk mice by correction of anemia by parenteral iron. Based on studies of
these mutants, distinct apical and basolateral iron transport systems possibly exist that function coordinately
to transfer iron from intestinal lumen to plasma.
ÝWhatever the mechanism of iron uptake, normally only about 10% of the elemental iron entering the
duodenum is absorbed. However, this value increases markedly with iron deficiency (Finch, 1994). In
contrast, iron overload reduces but does not eliminate absorption, reaffirming the fact that absorption is
regulated by body iron stores. In addition, both anemia and hypoxia boost iron absorption. A portion of the
iron that enters the mucosal cells is retained sequestered within ferritin. Intracellular intestinal iron is lost
when epithelial cells are sloughed from the lining of the gastrointestinal tract. The remaining iron traverses
the mucosal cells, to be coupled to transferrin for transport through the circulation.
Erythropoiesis and Iron Absorption
ÝApproximately 80% of total body iron is ultimately incorporated into red cell hemoglobin. An average
adult produces 2 x 1011 red cells daily, for a red cell renewal rate of 0.8 percent per day. Each red cell
contains more than a billion atoms of iron, and each ml of red cells contains 1 mg of iron. To meet this
daily need for 2 x 1020 atoms (or 20 mg) of elemental iron, the body has developed regulatory mechanisms
whereby erythropoiesis profoundly influences iron absorption. Plasma iron turnover (PIT) represents the
mass turnover of transferrin-bound iron in the circulation, expressed as mg/kg/day (Huff et al., 1950).
Accelerated erythropoiesis increases plasma iron turnover, which is associated with enhanced iron uptake
from the gastrointestinal tract (Weintraub et al., 1965). The mechanism by which PIT alters iron absorption
is unknown.
ÝA circulating factor related to erythropoiesis that modulates iron absorption has been hypothesized, but not
identified (Beutler and Buttenweiser, 1960); (Finch, 1994). Several candidate factors have been excluded,
including transferrin (Aron et al., 1985) and erythropoietin (Raja et al., 1986). Clinical manifestations of this
apparent communication between the marrow and the intestine includes iron overload that develops in
patients with severe thalassemia in the absence of transfusion. The accelerated (but ineffective)
erythropoiesis in this condition substantially boosts iron absorption. In some cases, the coupling of increased
PIT and increased gastrointestinal iron absorption is beneficial. In pregnancy, placental removal of iron
raises the PIT. This process enhances gastrointestinal iron absorption thereby increasing the availability of
the element to meet the needs of the growing and developing fetus.
ÝCompetition studies suggest that several other heavy metals share the iron intestinal absorption pathway.
These include lead, manganese, cobalt and zinc (Table 1). Enhanced iron absorption induced by iron
deficiency also augments the uptake of these elements. As iron deficiency often coexists with lead
intoxication, this interaction can produce particularly serious medical complications in children (Piomelli et
al., 1987). Interestingly, copper absorption and metabolism appear to be handled mechanisms different to
those of iron.
References:
Andrews NC. (2000). Intestinal iron absorption: current concepts circa 2000. Dig Liver Dis Jan-
Feb;32(1):56-61.
Banerjee, D., Flanagan, P. R., Cluett, J., and Valberg, L. S. (1986). Transferrin receptors in the human
gastrointestinal tract. Relationship to body iron stores. Gastroenterology 91, 861.
Bannerman, R. M. (1976). Genetic defects of iron transport. Federation Proceedings 35, 2281.
Beutler, E., and Buttenweiser, E. (1960). The regulation of iron absorption. I. A search for humoral
factors. Journal of Laboratory and Clinical Medicine 55, 274.
Bezwoda, W. R., MacPhail, A. P., Bothwell, T. H., Baynes, R. D., Derman, D. P., and Torrance, J. D.
(1986). Failure of transferrin to enhance iron absorption in achlorhydric human subjects. Br. J.
Haematol. 63, 749.
Bothwell, T. H., and Charlton, R. W. (1982). A general approach of the problems of iron deficiency
and iron overload in the population at large. Seminars in Hematology 19, 54.
Cartwright, G. E., Gubler, C. J., Bush, J. A., and Wintrobe, M. M. (1956). Studies on copper
metabolism. XVII. Further observations on the anemia of copper deficiency in swine. Blood 11, 143.
Conrad, M. E., and Umbreit, J. N. (1993). A concise review: Iron absorption - the mucin-mobilferrinintegrin
pathway. A competitive pathway for metal absorption. American Journal of Hematology 42,
67.
Cook, J. D., Skikne, B. S., and al., e. (1986). Estimates of iron sufficiency in the US population.
Blood 68, 726.
Craven, C. M., Alexander, J., Eldridge, M., Kushner, J. P., Bernstein, S., and Kaplan, J. (1987).
Tissue distribution and clearance kinetics of non-transferrin-bound iron in the hypotransferrinemic
mouse: a rodent model for hemochromatosis. Proceedings of the National Academy of Sciences
(USA) 84, 3457.
Dancis, A., Haile, D., Yuan, D.S., Klausner, R.D. (1994). The Saccharomyces cerevisiae copper
transport protein (Ctr1p). Biochemical characterization, regulation by copper, and physiologic role in
copper uptake. J. Biol. Chem. 269, 25660-7
De Silva, D. M., Askwith, C. C., Eide, D., and Kaplan, J. (1995). The FET3 gene product required for
high affinity iron transport in yeast is a cell surface ferroxidase. Journal of Biological Chemistry 270,
1098-101.
Finch, C. (1994). Regulators of iron balance in humans. Blood 84, 1697.
Gibson, R. S., MacDonald, A. C., and Smit-Vanderkooy, P. D. (1988). Serum ferritin and dietary iron
parameters in a sample of Canadian preschool children. J. Can. Dietetic Assoc. 49, 23.
Goyer, RA. (1993) Lead toxicity: current concerns. Environ Health Perspect 100: 177-187.
Gubler, C. J., Lahey, M. E., Chase, M. S., Cartwright, G. E., and Wintrobe, M. M. (1952). Studies on
copper metabolism. III. The metabolism of iron in copper deficient swine. Blood 7, 1075.
Harford, J. B., Rouault, T. A., Huebers, H. A., and Klausner, R. D. (1994). Molecular mechanisms of
iron metabolism. In The Molecular Basis of Blood Diseases, G. Stamatoyannopoulos, A. W. Nienhuis,
P. W. Majerus and H. Varmus, eds. (Philadelphia: W.B. Saunders Co.), pp. 351-378.
Heilmeyer, L., Keller, W., Vivell, O. Keiderling, W., Betke, K., Wohler, F., Schultze, H.E. (1961)
Congenital transferrin deficiency in a seven-year old girl. German Medical Monthly 6, 385
Iron Absorption 7/27/08 1:23 PM
http://sickle.bwh.harvard.edu/iron_absorption.html Page 6 of 6
Huebers, H. A., Huebers, E., and al., e. (1983). The significance of transferrin for intestinal iron
absorption. Blood 61, 283.
Huff, R. L., Hennessey, T. G., Austin, R. E., Garcia, J. F., Roberts, B. M., and Lawrence, J. H.
(1950). Plasma and red cell iron turnover in normal subjects and in patients having various
hematopoietic disorders. Journal of Clinical Investigation 29, 1041.
Idzerda, R. L., Huebers, H., and al., e. (1986). Rat transferrin gene expression: tissue-specific
regulation by iron deficiency. Proceedings of the National Academy of Sciences (USA) 83, 3723.
Kappas, A., Drummond, G. S., and Galbraith, R. A. (1993). Prolonged clinical use of a heme
oxygenase inhibitor: hematological evidence for an inducible but reversible iron-deficiency state.
Pediatrics 91, 537-539.
Klausner R.D., van Renswoude J., Ashwell G., Kempf, C, Schechter, AN, Dean, A, Bridges, KR.
(1983) Receptor-mediated endocytosis of transferrin in K562 cells. J. Biol. Chem. 258: 4715 - 4724.
Lahey, M. E., Gubler, C. J., Chase, M. S., Cartwright, G. E., and Wintrobe, M. M. (1952). Studies on
copper metabolism. II. Hematologic manifestations of copper deficiency in swine. Blood 7, 1075.
Levin, M. J., Tuil, D., and al., e. (1984). Expression of transferrin gene during development of nonhepatic
tissues: High level of transferrin mRNA in fetal muscle and adult brain. Biochem. Biophys.
Res. Commun. 122, 212.
McCance, R. A., and Widdowson, E. M. (1938). The absorption and excretion of iron following oral
and intravenous administration. J. Phys. 94, 148.
Muir, A., and Hopfer, U. (1985). Regional specificity of iron uptake by smal intestinal brush-boarder
membranes from normal and iron deficient mice. Gastrointestinal and Liver Pathology 11, 6376-6379.
Parmley, R. T., Barton, J. C., and Conrad, M. E. (1985). Ultrastructural localization of transferrin,
transferrin receptor and iron-binding sites on human placental and duodenal microvilli. Br. J.
Haematol. 60, 81.
Piomelli, S., Seaman, C., and Kapoor, S. (1987). Lead-induced abnormalities of porphyrin
metabolism. The relationship with iron deficiency. Ann. NY Acad. Sci. 514, 278.
Raja, K. N., Pippard, M. J., Simpson, R. J., and Peters, T. J. (1986). Relationship between
erythropoiesis and the enhanced intestinal uptake of ferric iron in hypoxia in the mouse. British
Journal of Haematology 64, 587.
Schumann, K., Schafer, S. G., and Forth, W. (1986). Iron absorption and biliary excretion of
transferrin in rats. Res. Exp. Med. 186, 215.
Simpson, R. J., Osterloh, K. R. S., Raja, K. B., Snape, S. D., and Peters, T. J. (1986). Studies on the
role of transferrin and endocytosis on the uptake of Fe3+ from Fe-nitriloacetate by mouse duodenum.
Biochim. Biophys. Acta 884, 166.
Stearman, R., Yuan, D. S., Yamaguchi-Iwai, Y., Klausner, R. D., and Dancis, A. (1996). A permeaseoxidase
complex involved in high-affinity iron uptake in yeast. Science 271, 1552-1557.
Weintraub, L. R., Conrad, M. E., and Crosby, W. H. (1965). Regulation of the intestinal absorption of
iron by the rate of erythropoiesis. British Journal of Hematology 2, 432.
Yuan, D. S., Stearman, R., Dancis, A., Dunn, T., Beeler, T., and Klausner, R. D. (1995). The
Menkes/Wilson disease gene homologue in yeast provides copper to a ceruloplasmin-like oxidase
required for iron uptake. Proceedings of the National Academy of Sciences (USA) 92, 2632-2636.
Wednesday, July 16, 2008
Shingles vaccine .. Pros and Cons
Maybe you haven't heard anything about the shingles vaccine. Or maybe you have, but decided against getting it for any of a number of reasons like these:
- Although it has been approved by the U.S. Food and Drug Administration and by the European Commission for people 60 and older, you are only 45.
- It protects just half of those vaccinated, and you would just as soon take your chances.
- No one yet knows how long the benefits will last.
- No one yet knows about delayed side effects.
- You do not know anything about shingles, so how common or bad can it be?
- Your insurance does not cover it.
Before dismissing the vaccine entirely, you may want to consider Merritt ClappSmith's recent encounter with shingles. Although at 39 she is much younger than the typical shingles patient, her experience with confusing symptoms and a twice-missed diagnosis occurs at all ages. This is her story:
"My shingles case began with the periodic sensation that bugs were crawling in my hair. Three weeks later, I developed a headache that was one-sided but unlike a migraine. The pain was so bad I couldn't go to work. That evening, I discovered a raised and very tender ridge on my scalp.
"Unable to sleep and in terrible pain, I went to the local emergency room. The doctor there gave me an intravenous painkiller, tested me for meningitis or encephalitis, and concluded that I had a migraine and infected hair follicle.
"The terrible head pain grew, as did the sensitivity of the rash, and at 3 a.m. the next day, my husband drove me to a major hospital. The doctor cursorily looked at the blistering rash and treated me for a migraine. He had no explanation for the rash.
"After another horrible night and day of pain and a growing rash, my husband drove me to Urgent Care, where a nurse immediately suspected shingles, and the doctor concluded 'shingles' in 30 seconds. I got acyclovir for the virus and Vicodin for pain. I slept a lot, and my eye swelled. When the blisters scabbed over, I returned to work, but I was so tired and my eye was so sensitive to light that I had to cut short my workdays."
ClappSmith, an urban planner from St. Paul, Minnesota, said that after her experience she encouraged her mother, who is 71, to get the shingles vaccine. But that decision is not always simple.
Shingles, or herpes zoster, can afflict anyone who has had chickenpox. Both are caused by the varicella zoster virus. It is not known whether shingles can develop in people who received the chickenpox vaccine, which contains a live attenuated form of the virus.
This virus never leaves the body. It lies dormant for years in nerve roots near the spinal cord and can be reactivated as a shingles infection at any time, especially in people whose immune system is weakened by advanced age, extreme stress, a disease like cancer or AIDS or medications like chemotherapy, steroids and drugs used to prevent organ rejection. Sometimes, a physical stress like cold or sunburn can bring on an attack.
Reactivated, the virus migrates down the nerve until it reaches the skin, where it causes vague symptoms of irritation, pain, numbness, itching or tingling, followed in two or three days by a painful, blistering rash on one side of the face, head or body. Untreated, the rash lasts two to four weeks.
The pain can be severe and may be accompanied by headache, fever, chills and an upset stomach. In rare cases, it can lead to pneumonia, hearing loss, blindness, encephalitis and, rarer still, death.
After the rash clears, about one patient in five develops post-herpetic neuralgia, or PHN, a debilitating pain that does not always respond to treatment and can be devastating to ordinary life for months or even years.
Treatment with the antiviral drug acyclovir is best administered as early as possible, preferably within 72 hours of the first sign of a rash, to shorten the course of the disease and prevent the severe symptoms that ClappSmith experienced. Anti-viral drugs, if taken early, can reduce the severity of subsequent post-herpetic neuralgia, but starting anti-virals after PHN develops is of no help.
About one million cases of shingles a year occur in the United States, and the risk of it and of PHN increases with age. Half of 85-year-olds will have had shingles and, as people age, shingles-associated nerve pain increases in frequency and severity.
Debilitating nerve pain occurs in nearly a third of people with shingles who are 60 or older, and about 12 percent of older people who have shingles have pain that lasts three months or longer. The pain of PHN, which is difficult to treat, has been described as burning, throbbing, aching, stabbing or shooting. Even clothing touching the skin or a cool breeze can cause excruciating pain.
The shingles vaccine, Zostavax by Merck, was licensed in May 2006 in the United States after a study of more than 38,500 men and women 60 and older showed that it prevented about half of cases of shingles and reduced the risk of PHN by two-thirds.
"Among vaccine recipients who did get shingles, the episodes generally were far milder than they otherwise would have been," said Dr. Stephen Straus, an infectious disease specialist at the National Institute of Allergy and Infectious Diseases.
The vaccine, given in a single dose by injection, contains the same attenuated virus as the chickenpox vaccine, but is 14 times as potent.
The side effects have been minimal, usually redness, soreness, swelling or itching at the injection site and, rarely, headaches.
Based on the study, the researchers estimated that the vaccine could prevent 250,000 cases of shingles a year in the United States and significantly reduce its severity and complications in another 250,000 people. The vaccine is most effective in people 60 to 69, and less so with advancing age.
The vaccine is approved for use in people 60 and older who have had chickenpox. The Advisory Committee on Immunization Practices for the Centers for Disease Control and Prevention recommended that it be given to people who have had shingles, though the chances of another attack are low. The manufacturer's price for the vaccine is about $150. The patients' cost in the United States is often $300.
Because people in their 50s account for one in every seven cases of shingles, some physicians administer the vaccine "off label" to those younger than 60, even though its safety and effectiveness in younger people are not known. Also unknown is whether the vaccine is safe to administer to people whose immune systems are already weakened.
Follow-up studies are under way to determine how long the vaccine remains effective. If immunity wanes, a booster shot may be necessary.
Until the unknowns are resolved, the vaccine is not recommended for those with immune systems weakened by disease or drug treatment, women who are pregnant or might be pregnant and people with active untreated tuberculosis. Nor should the vaccine be given to anyone who has had a life-threatening allergic reaction to gelatin or the antibiotic neomycin.
- Although it has been approved by the U.S. Food and Drug Administration and by the European Commission for people 60 and older, you are only 45.
- It protects just half of those vaccinated, and you would just as soon take your chances.
- No one yet knows how long the benefits will last.
- No one yet knows about delayed side effects.
- You do not know anything about shingles, so how common or bad can it be?
- Your insurance does not cover it.
Before dismissing the vaccine entirely, you may want to consider Merritt ClappSmith's recent encounter with shingles. Although at 39 she is much younger than the typical shingles patient, her experience with confusing symptoms and a twice-missed diagnosis occurs at all ages. This is her story:
"My shingles case began with the periodic sensation that bugs were crawling in my hair. Three weeks later, I developed a headache that was one-sided but unlike a migraine. The pain was so bad I couldn't go to work. That evening, I discovered a raised and very tender ridge on my scalp.
"Unable to sleep and in terrible pain, I went to the local emergency room. The doctor there gave me an intravenous painkiller, tested me for meningitis or encephalitis, and concluded that I had a migraine and infected hair follicle.
"The terrible head pain grew, as did the sensitivity of the rash, and at 3 a.m. the next day, my husband drove me to a major hospital. The doctor cursorily looked at the blistering rash and treated me for a migraine. He had no explanation for the rash.
"After another horrible night and day of pain and a growing rash, my husband drove me to Urgent Care, where a nurse immediately suspected shingles, and the doctor concluded 'shingles' in 30 seconds. I got acyclovir for the virus and Vicodin for pain. I slept a lot, and my eye swelled. When the blisters scabbed over, I returned to work, but I was so tired and my eye was so sensitive to light that I had to cut short my workdays."
ClappSmith, an urban planner from St. Paul, Minnesota, said that after her experience she encouraged her mother, who is 71, to get the shingles vaccine. But that decision is not always simple.
Shingles, or herpes zoster, can afflict anyone who has had chickenpox. Both are caused by the varicella zoster virus. It is not known whether shingles can develop in people who received the chickenpox vaccine, which contains a live attenuated form of the virus.
This virus never leaves the body. It lies dormant for years in nerve roots near the spinal cord and can be reactivated as a shingles infection at any time, especially in people whose immune system is weakened by advanced age, extreme stress, a disease like cancer or AIDS or medications like chemotherapy, steroids and drugs used to prevent organ rejection. Sometimes, a physical stress like cold or sunburn can bring on an attack.
Reactivated, the virus migrates down the nerve until it reaches the skin, where it causes vague symptoms of irritation, pain, numbness, itching or tingling, followed in two or three days by a painful, blistering rash on one side of the face, head or body. Untreated, the rash lasts two to four weeks.
The pain can be severe and may be accompanied by headache, fever, chills and an upset stomach. In rare cases, it can lead to pneumonia, hearing loss, blindness, encephalitis and, rarer still, death.
After the rash clears, about one patient in five develops post-herpetic neuralgia, or PHN, a debilitating pain that does not always respond to treatment and can be devastating to ordinary life for months or even years.
Treatment with the antiviral drug acyclovir is best administered as early as possible, preferably within 72 hours of the first sign of a rash, to shorten the course of the disease and prevent the severe symptoms that ClappSmith experienced. Anti-viral drugs, if taken early, can reduce the severity of subsequent post-herpetic neuralgia, but starting anti-virals after PHN develops is of no help.
About one million cases of shingles a year occur in the United States, and the risk of it and of PHN increases with age. Half of 85-year-olds will have had shingles and, as people age, shingles-associated nerve pain increases in frequency and severity.
Debilitating nerve pain occurs in nearly a third of people with shingles who are 60 or older, and about 12 percent of older people who have shingles have pain that lasts three months or longer. The pain of PHN, which is difficult to treat, has been described as burning, throbbing, aching, stabbing or shooting. Even clothing touching the skin or a cool breeze can cause excruciating pain.
The shingles vaccine, Zostavax by Merck, was licensed in May 2006 in the United States after a study of more than 38,500 men and women 60 and older showed that it prevented about half of cases of shingles and reduced the risk of PHN by two-thirds.
"Among vaccine recipients who did get shingles, the episodes generally were far milder than they otherwise would have been," said Dr. Stephen Straus, an infectious disease specialist at the National Institute of Allergy and Infectious Diseases.
The vaccine, given in a single dose by injection, contains the same attenuated virus as the chickenpox vaccine, but is 14 times as potent.
The side effects have been minimal, usually redness, soreness, swelling or itching at the injection site and, rarely, headaches.
Based on the study, the researchers estimated that the vaccine could prevent 250,000 cases of shingles a year in the United States and significantly reduce its severity and complications in another 250,000 people. The vaccine is most effective in people 60 to 69, and less so with advancing age.
The vaccine is approved for use in people 60 and older who have had chickenpox. The Advisory Committee on Immunization Practices for the Centers for Disease Control and Prevention recommended that it be given to people who have had shingles, though the chances of another attack are low. The manufacturer's price for the vaccine is about $150. The patients' cost in the United States is often $300.
Because people in their 50s account for one in every seven cases of shingles, some physicians administer the vaccine "off label" to those younger than 60, even though its safety and effectiveness in younger people are not known. Also unknown is whether the vaccine is safe to administer to people whose immune systems are already weakened.
Follow-up studies are under way to determine how long the vaccine remains effective. If immunity wanes, a booster shot may be necessary.
Until the unknowns are resolved, the vaccine is not recommended for those with immune systems weakened by disease or drug treatment, women who are pregnant or might be pregnant and people with active untreated tuberculosis. Nor should the vaccine be given to anyone who has had a life-threatening allergic reaction to gelatin or the antibiotic neomycin.
Sunday, July 13, 2008
Hepatitis C - The Facts
What is hepatitis C?
Hepatitis C is a disease caused by the hepatitis C virus which results in infection of the liver. Hepatitis C is the most common (but not the only) cause of post-transfusion hepatitis in the United States.
Who gets hepatitis C?
Anyone can get hepatitis C, but IV drug users, transfusion recipients, and dialysis patients are at high risk of getting the infection. Health care workers who have frequent contact with blood have also been shown to be at risk.
How is the virus spread?
The hepatitis C virus is spread by contact with contaminated blood or plasma. Contaminated needles and syringes are a source of spread among IV drug users. The role of person-to-person contact and sexual activity in the spread of this disease is unclear. While spread may occur by these routes, it is less frequent than with the hepatitis B virus.
Hepatitis C virus is NOT spread through casual contact or in typical school, office, or food service settings. It is NOT spread by coughing, sneezing, or drinking out of the same glass.
What are the symptoms?
Symptoms develop slowly and may include loss of appetite, stomach pain, nausea, vomiting. Jaundice (yellowing of the skin or whites of the eyes) does not occur as commonly with hepatitis C as it does with hepatitis B. The severity of the illness can range from no symptoms to fatal cases (rare). Long-term infection is common. Liver disease may result from long-term infection, but the illness more often improves after two to three years. People who have a long term infection may or may not have symptoms. People who do not have symptoms can spread disease.
How soon do the symptoms appear?
Symptoms commonly appear within six to nine weeks. However, they can occur as soon as two weeks and as long as six months after infection.
How long can an infected person spread the virus?
Infected people may spread the virus indefinitely.
How is hepatitis C diagnosed?
A positive blood test for hepatitis C virus antibody can mean any of the following:
Current or acute infection - This diagnosis is usually made if a person has signs and symptoms of liver disease, blood tests showing abnormal liver function, and negative tests for hepatitis A and B.
Chronic carrier - A chronic carrier is a person who was infected more than 6 months prior to the positive antibody blood test. The carrier does not have signs or symptoms of liver disease although there may be abnormal liver function tests. The carrier can transmit the virus to others. Over time the virus may cause liver damage, carriers should be followed closely by a physician. If there is evidence of progressive liver damage, the patient should be referred to a doctor specializing in the treatment of liver disease.
Immunity - The person was infected with hepatitis C in the past but has cleared the virus from their body. The person has a positive hepatitis C antibody test, no signs or symptoms of liver disease, and normal liver function tests. The immune person cannot spread hepatitis C to anyone else, and the antibodies protect them from infection in the future.
False Positive Test - The blood test is not 100% accurate. Rarely, the test is positive even though the person has never been infected with hepatitis C. There is no evidence of liver disease. Repeat hepatitis C antibody tests may be negative.
How good is the blood test?
The hepatitis C test used by blood donation centers is only a screening test to eliminate hepatitis C virus from the nation’s blood and plasma supply. Individuals who test positive on the hepatitis C virus antibody test should be retested using the RIBA hepatitis C test or testing for hepatitis C virus using PCR technology. These tests cannot determine whether the disease is acute or chronic.
How can hepatitis C be prevented?
Syringes, tattooing, and acupuncture needles should not be reused. Control measures against hepatitis B infection also apply. Blood banks should properly discard units of blood that are positive for the hepatitis C virus.
UTAH DEPARTMENT OF HEALTH
BUREAU OF EPIDEMIOLOGY
August 2001
Hepatitis C is a disease caused by the hepatitis C virus which results in infection of the liver. Hepatitis C is the most common (but not the only) cause of post-transfusion hepatitis in the United States.
Who gets hepatitis C?
Anyone can get hepatitis C, but IV drug users, transfusion recipients, and dialysis patients are at high risk of getting the infection. Health care workers who have frequent contact with blood have also been shown to be at risk.
How is the virus spread?
The hepatitis C virus is spread by contact with contaminated blood or plasma. Contaminated needles and syringes are a source of spread among IV drug users. The role of person-to-person contact and sexual activity in the spread of this disease is unclear. While spread may occur by these routes, it is less frequent than with the hepatitis B virus.
Hepatitis C virus is NOT spread through casual contact or in typical school, office, or food service settings. It is NOT spread by coughing, sneezing, or drinking out of the same glass.
What are the symptoms?
Symptoms develop slowly and may include loss of appetite, stomach pain, nausea, vomiting. Jaundice (yellowing of the skin or whites of the eyes) does not occur as commonly with hepatitis C as it does with hepatitis B. The severity of the illness can range from no symptoms to fatal cases (rare). Long-term infection is common. Liver disease may result from long-term infection, but the illness more often improves after two to three years. People who have a long term infection may or may not have symptoms. People who do not have symptoms can spread disease.
How soon do the symptoms appear?
Symptoms commonly appear within six to nine weeks. However, they can occur as soon as two weeks and as long as six months after infection.
How long can an infected person spread the virus?
Infected people may spread the virus indefinitely.
How is hepatitis C diagnosed?
A positive blood test for hepatitis C virus antibody can mean any of the following:
Current or acute infection - This diagnosis is usually made if a person has signs and symptoms of liver disease, blood tests showing abnormal liver function, and negative tests for hepatitis A and B.
Chronic carrier - A chronic carrier is a person who was infected more than 6 months prior to the positive antibody blood test. The carrier does not have signs or symptoms of liver disease although there may be abnormal liver function tests. The carrier can transmit the virus to others. Over time the virus may cause liver damage, carriers should be followed closely by a physician. If there is evidence of progressive liver damage, the patient should be referred to a doctor specializing in the treatment of liver disease.
Immunity - The person was infected with hepatitis C in the past but has cleared the virus from their body. The person has a positive hepatitis C antibody test, no signs or symptoms of liver disease, and normal liver function tests. The immune person cannot spread hepatitis C to anyone else, and the antibodies protect them from infection in the future.
False Positive Test - The blood test is not 100% accurate. Rarely, the test is positive even though the person has never been infected with hepatitis C. There is no evidence of liver disease. Repeat hepatitis C antibody tests may be negative.
How good is the blood test?
The hepatitis C test used by blood donation centers is only a screening test to eliminate hepatitis C virus from the nation’s blood and plasma supply. Individuals who test positive on the hepatitis C virus antibody test should be retested using the RIBA hepatitis C test or testing for hepatitis C virus using PCR technology. These tests cannot determine whether the disease is acute or chronic.
How can hepatitis C be prevented?
Syringes, tattooing, and acupuncture needles should not be reused. Control measures against hepatitis B infection also apply. Blood banks should properly discard units of blood that are positive for the hepatitis C virus.
UTAH DEPARTMENT OF HEALTH
BUREAU OF EPIDEMIOLOGY
August 2001
Traveling to Costa Rica - be prepared
Travel to Costa Rica has increased remarkably lately so I thought that I would post the recommended vaccinations so you can be prepared for travel.
Malaria: Prophylaxis with chloroquine is recommended for the provinces of Alajuela, Limon (except for Limon City), Guanacaste, and Heredia.
Vaccinations:
Hepatitis A Recommended for all travelers
Typhoid Recommended for all travelers
Hepatitis B For travelers who may have intimate contact with local residents, especially if visiting for more than 6 months
Yellow fever Required for travelers arriving from a yellow-fever-infected country in Africa or the Americas
Measles, mumps, rubella (MMR) Two doses recommended for all travelers born after 1956, if not previously given
Tetanus-diphtheria Revaccination recommended every 10 years
Malaria: Prophylaxis with chloroquine is recommended for the provinces of Alajuela, Limon (except for Limon City), Guanacaste, and Heredia.
Vaccinations:
Hepatitis A Recommended for all travelers
Typhoid Recommended for all travelers
Hepatitis B For travelers who may have intimate contact with local residents, especially if visiting for more than 6 months
Yellow fever Required for travelers arriving from a yellow-fever-infected country in Africa or the Americas
Measles, mumps, rubella (MMR) Two doses recommended for all travelers born after 1956, if not previously given
Tetanus-diphtheria Revaccination recommended every 10 years
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