-------------------------------------------------------------------------------- Requirements/Sources The official U.S. recommendations for daily intake of iron are as follows: Infants 06 months, 0.27 mg 712 months, 11 mg Children 13 years, 7 mg 48 years, 10 mg Males 913 years, 8 mg 1418 years, 11 mg 19 years and older, 8 mg Females 913 years, 8 mg 1418 years, 15 mg 1950 years, 18 mg 50 years and older, 8 mg Pregnant women, 27 mg Nursing women 9 mg, (10 mg if 18 years old or younger) Iron deficiency is the most common nutrient deficiency in the world; worldwide, at least 700 million individuals have iron-deficiency anemia.1 While iron deficiency is widespread in the developing world, it is also prevalent in developed countries. Groups at high risk are children, teenage girls, menstruating women, pregnant women, and the elderly.2,3 There are two major forms of iron: heme iron and nonheme iron. Heme iron is bound to the proteins hemoglobin or myoglobin, whereas nonheme iron is an inorganic compound. (In chemistry, "organic" has a very precise meaning that has nothing to do with farming. An organic compound contains carbon atoms. Thus "inorganic iron" is an iron compound containing no carbon.) Heme iron, obtained from red meats and fish, is easily absorbed by the body. Nonheme iron, derived from plants, is less easily absorbed. Rich sources of heme iron include oysters, meat, poultry, and fish.The main sources of nonheme iron are dried fruits, molasses, whole grains, legumes, egg yolks, leafy green vegetables, nuts, seeds, and kelp. Acidic foods, such as fruit preserves and tomatoes, are a good source of iron when they've been cooked in iron or stainless steel cookware (some of the iron leaches into the food). Iron absorption may be affected by the following substances: antibiotics in the quinolone (Floxin, Cipro)48 or tetracycline9,10,11 families, levodopa,12 methyldopa,13,14 carbidopa,15 penicillamine,16 thyroid hormone,17 captopril (and possibly other ACE inhibitors),18 calcium,1922 soy,23 zinc,24 copper,25 or manganese.26 Conversely, iron may inhibit their absorption, too. In addition, drugs in the H2 blocker or proton pump inhibitor families may impair iron absorption.27 -------------------------------------------------------------------------------- Therapeutic Dosages The typical short-term therapeutic dosage to correct iron deficiency is 100 to 200 mg daily. Once your body's iron stores reach normal levels, however, this dose should be reduced to the lowest level that can maintain iron balance. -------------------------------------------------------------------------------- Therapeutic Uses The most obvious use of iron supplements is to treat iron deficiency. Severe iron deficiency causes anemia, which in turn causes many symptoms. Iron deficiency too slight to cause anemia appears to impair health as well. A double-blind trial suggests that women with mild iron deficiency might have difficulty increasing their physical fitness.28 In addition, an observational study suggests that adolescent girls who are marginally iron deficient may experience reduced mental function.29 However, don't take iron just because you feel tired. Make sure to get tested to see whether you are indeed deficient. With iron, more is definitely not better. Heavy menstruation (menorrhagia) can certainly cause iron loss. Iron has also been tried as a treatment for attention deficit disorder, but there is as yet no real evidence that it works. Preliminary studies have linked low iron levels to restless legs syndrome.30,31,32 However, a small double-blind study found no benefit with iron supplements among individuals who were not iron deficient.33 A study of 71 HIV-positive children noted a high rate of iron deficiency.34 One observational study of 296 men with HIV infection linked high intake of iron to a decreased risk of AIDS 6 years later.35 Individuals taking ACE inhibitors frequently develop a dry cough as a side effect. One study suggests that iron supplementation can alleviate this symptom.50 (However, iron can interfere with ACE inhibitor absorption, so it should be taken at a different time of day.) -------------------------------------------------------------------------------- What Is the Scientific Evidence for Iron? Sports Performance A double-blind placebo-controlled trial of 42 non-anemic women with evidence of slightly low iron reserves found that iron supplements significantly increased the benefits gained from exercise.36 Participants were put on a daily aerobic training program for the latter 4 weeks of this 6-week trial. At the end of the trial, those receiving iron showed significantly greater gains in speed and endurance as compared to those given placebo. In addition, a double-blind placebo-controlled study of 40 non-anemic elite athletes with mildly low iron stores found that 12 weeks of iron supplementation enhanced aerobic performance.37 Menorrhagia One small double-blind study found good results using iron supplements to treat heavy menstruation. This study, which was performed in 1964, saw an improvement in 75% of the women who took iron (compared to 32.5% of those who took placebo). Women who began with higher iron levels did not respond to treatment.38 This suggests once more that supplementing with iron is only a good idea if you are deficient in it. -------------------------------------------------------------------------------- Safety Issues At the recommended dosage, iron is quite safe. Excessive dosages, however, can be toxicdamaging the intestines and liver, and possibly resulting in death. Iron poisoning in children is a surprisingly common problem, so make sure to keep your iron supplements out of their reach. Mildly excessive levels of iron may be unhealthy for another reason: it acts as an oxidant (the opposite of an antioxidant), perhaps increasing the risk of cancer and heart disease, although this is controversial.39 Elevated levels of iron may also play a role in brain injury caused by stroke.40 In addition, excess iron appears to increase complications of pregnancy.41 Simultaneous use of iron and high-dose vitamin C can cause excessive iron absorption.4249 -------------------------------------------------------------------------------- Interactions You Should Know About If you are taking Antibiotics in the tetracycline or quinolone (Floxin, Cipro)families, levodopa, methyldopa, carbidopa, penicillamine, thyroid hormone, calcium , soy, zinc, copper, or manganese:To avoid absorption problems, wait at least 2 hours following your dose of medication or supplement before taking iron. Drugs that reduce stomach acid such as antacids, H2 blockers and proton pump inhibitors: You may need extra iron. High doses of vitamin C: You may absorb too much iron. ACE inhibitors: Iron may reduce coughing side effect; however, to avoid absorption problems, you should wait at least 2 hours following your dose of medication before taking iron. -------------------------------------------------------------------------------- References 1. Shils ME, Olson JA, Shike M, eds. Modern Nutrition in Health and Disease. 9th ed. Baltimore: Williams & Wilkins; 1999: 1772. 2. Shils ME, Olson JA, Shike M, eds. Modern Nutrition in Health and Disease. 9th ed. Baltimore: Williams & Wilkins; 1999: 210, 860, 1422, 1424. 3. Nelson M, Ash R, Mulvhill C, et al. Iron status, diet and cognitive function in British adolescent girls. Poster presented at: The Nutrition Society's Nutrition 2000 Research Themes for the New Millenium; June 2630; University College, Cork, Ireland. 4. Kara M, Hasinoff BB, McKay DW, et al. Clinical and chemical interactions between iron preparations and ciprofloxacin. Br J Clin Pharmacol. 1991;31:257261. 5. Polk RE, Healy DP, Sahai J, et al. Effect of ferrous sulfate and multivitamins with zinc on absorption of ciprofloxacin in normal volunteers. Antimicrob Agents Chemother. 1989;33:18411844. 6. Campbell NR, Kara M, Hasinoff BB, et al. Norfloxacin interaction with antacids and minerals. Br J Clin Pharmacol. 1992;33:115116. 7. Lehto P, Kivisto KT. Different effects of products containing metal ions on the absorption of lomefloxacin. Clin Pharmacol Ther. 1994;56:477482. 8. Lehto P, Kivisto KT, and Neuvonen PJ. The effect of ferrous sulphate on the absorption of norfloxacin, ciprofloxacin and ofloxacin. Br J Clin Pharmacol. 1994;37:8285. 9. Neuvonen PJ. Interactions with the absorption of tetracyclines. Drugs. 1976;11:4554. 10. Campbell NR, Hasinoff BB. Iron supplements: a common cause of drug interactions. Br J Clin Pharmacol. 1991;31:251255. 11. Heinrich HC, Oppitz KH, Gabbe EE. Inhibition of iron absorption in man by tetracycline [in German]. Klin Wochenschr. 1974;52:493498. 12. Campbell NR, Hasinoff BB. Iron supplements: a common cause of drug interactions. Br J Clin Pharmacol. 1991;31:251255. 13. Campbell N, Paddock V, Sundaram R. Alteration of methyldopa absorption, metabolism, and blood pressure control caused by ferrous sulfate and ferrous gluconate. Clin Pharmacol Ther. 1988;43:381386. 14. Campbell NR, Hasinoff BB. Iron supplements: a common cause of drug interactions. Br J Clin Pharmacol. 1991;31:251255. 15. Campbell NR, Hasinoff BB. Iron supplements: a common cause of drug interactions. Br J Clin Pharmacol. 1991;31:251255. 16. Osman MA, Patel RB, Schuna A, et al. Reduction in oral penicillamine absorption by food, antacid, and ferrous sulfate. Clin Pharmacol Ther. 1983;33:465470. 17. Campbell NR, Hasinoff BB, Stalts H, et al. Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism. Ann Intern Med. 1992;117:10101013. 18. Campbell NR, Hasinoff BB. Iron supplements: a common cause of drug interactions. Br J Clin Pharmacol. 1991;31:251255. 19. Hallberg L. Does calcium interfere with iron absorption? Am J Clin Nutr. 1998;68:34. 20. Cook JD, Dassenko SA, Whittaker P. Calcium supplementation: effect on iron absorption. Am J Clin Nutr. 199153:106111. 21. Dawson-Hughes B, Seligson FH, Hughes VA. Effects of calcium carbonate and hydroxyapatite on zinc and iron retention in postmenopausal women. Am J Clin Nutr. 1986;44:8388. 22. Sokoll LJ, Dawson-Hughes B. Calcium supplementation and plasma ferritin concentrations in premenopausal women. Am J Clin Nutr. 1992;56:10451048. 23. Hallberg L, Rossander L, Skanberg AB. Phytates and the inhibitory effects of bran on iron absorption in man. Am J Clin Nutr. 1987;45:988996. 24. Sandstrom B, Davidsson L, Cederblad A, et al. Oral iron, dietary ligands and zinc absorption. J Nutr. 1985;115:411414. 25. Haschke F, Ziegler EE, Edwards BB, et al. Effect of iron fortification of infant formula on trace mineral absorption. J Pediatr Gastroenterol Nutr. 1986;5:768773. 26. Freeland-Graves JH. Manganese: an essential nutrient for humans. Nutr Today. 1988;23:1319. 27. Champagne ET. Low gastric hydrochloric acid secretion and mineral bioavailability. Adv Exp Med Biol. 1989;249:173184. 28. Hinton PS, Giordano C, Brownlie T, et al. Iron supplementation improves endurance after training in iron-depleted, nonanemic women. J Appl Physiol. 2000;88:11031111. 29. Nelson M, Ash R, Mulvhill C, et al. Iron status, diet and cognitive function in British adolescent girls. Poster presented at: The Nutrition Society's Nutrition 2000Research Themes for the New Millennium; June 2630; University College, Cork, Ireland. 30. O'Keeffe ST. Restless legs syndrome. A review. Arch Intern Med. 1996;156:243248. 31. Sun ER, Chen CA, Ho G, et al. Iron and the restless legs syndrome. Sleep. 1998;21:371377. 32. O'Keeffe ST, Gavin K, Lavan JN. Iron status and restless legs syndrome in the elderly. Age Ageing. 1994;23:200203. 33. Davis BJ, Rajput A, Rajput ML, et al. A randomized, double-blind placebo-controlled trial of iron in restless legs syndrome. Eur Neurol. 2000;43:7075. 34. Castaldo A, Tarallo L, Palomba E, et al. Iron deficiency and intestinal malabsorption in HIV disease. J Pediatr Gastroenterol Nutr. 1996;22:359363. 35. Abrams B, Duncan D, Hertz-Picciotto I. A prospective study of dietary intake and acquired immune deficiency syndrome in HIV-seropositive homosexual men. J Acquir Immune Defic Syndr. 1993;6:949958. 36. Hinton PS, Giordano C, Brownlie T, et al. Iron supplementation improves endurance after training in iron-depleted, nonanemic women. J Appl Physiol. 2000;88:11031111. 37. Friedmann B, Weller E, Mairbaurl H, et al. 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Gastroenterology. 1968;55:3545. 44. Brise H, Hallberg L. Effect of ascorbic acid on iron absorption. Acta Med Scand. 1962;171(suppl 376):51. 45. Lynch SR, Cook JD. Interaction of vitamin C and iron. Ann N Y Acad Sci. 1980;355:3244. 46. Hunt JR, Gallagher SK, Johnson LK. Effect of ascorbic acid on apparent iron absorption by women with low iron stores. Am J Clin Nutr. 1994;59:13811385. 47. Diplock AT. Safety of antioxidant vitamins and beta-carotene. Am J Clin Nutr. 1995;62(suppl 6):1510S1516S. 48. Hoffman KE, Yanelli K, Bridges KR. Ascorbic acid and iron metabolism: alterations in lysosomal function. Am J Clin Nutr. 1991;54(suppl 6):1188S1192S. 49. Siegenberg D, Baynes RD, Bothwell TH, et al. Ascorbic acid prevents the dose-dependent inhibitory effects of polyphenols and phytates on nonheme-iron absorption. Am J Clin Nutr. 1991;53:537541. 50. Lee SC, Park SW, Kim DK, et al. Iron supplementation inhibits cough associated with ACE inhibitors. Hypertension. 2001;38:166170. |
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