Iron for Sports & Fitness

Also known as: Ferrous Sulphate

What is it?

Iron is an essential mineral. It is part of haemoglobin, the oxygen-carrying component of the blood. Iron-deficient people tire easily in part because their bodies are starved for oxygen. Iron is also part of myoglobin, which helps muscle cells store oxygen. Without enough iron, adenosine triphosphate (ATP; the fuel the body runs on) cannot be properly synthesised. As a result, some iron-deficient people become fatigued even when their haemoglobin levels are normal (i.e., when they are not anaemic).

Where is it found?

The most absorbable form of iron, called “heme” iron, is found in oysters, meat and poultry, and fish. Non-haem iron is also found in these foods, as well as in dried fruit, molasses, leafy green vegetables, wine, and iron supplements. Acidic foods (such as tomato sauce) cooked in an iron pan can also be a source of dietary iron.

Why do athletes use it?*

Some athletes say that iron

helps boost energy levels.

What do the advocates say?*

Athletes are not at risk of developing iron deficiency or anaemia any more than others; however, metabolically, athletes utilise more minerals, including iron, than non-athletes do.

Women have a greater risk of developing iron deficiency than men. Premenopausal women, in particular, are at risk of becoming iron-deficient because of the blood loss that occurs every month during menstruation.

Doctors often screen for iron deficiency by testing for anaemia. However, individuals who have a mild deficiency of iron may not be anaemic, since blood counts do not typically drop until iron stores in the body are almost completely depleted. If you suspect you are deficient in iron, ask your doctor to perform a more specific blood test, known as a “ferritin” test, rather than the routine “CBC” or “total iron” tests.

Prior to taking supplemental iron, people should be tested by a doctor to make sure such supplementation is appropriate. Although supplemental iron may help those who are deficient, too much iron may cause adverse side effects, including stomach and intestinal cramps, nausea, and constipation.

How much is usually taken by athletes?

Iron is important for an athlete because it is a component of haemoglobin, which transports oxygen to muscle cells. Some athletes, especially women, do not get enough iron in their diet. In addition, for reasons that are unclear, endurance athletes, such as marathon runners, frequently have low body-iron levels.¹ ² ³ However, anaemia in athletes is often not due to iron deficiency and may be a normal adaptation to the stress of exercise.⁴ Supplementing with iron is usually unwise unless a deficiency has been diagnosed. People who experience undue fatigue (an early warning sign of iron deficiency) should have their iron status evaluated by a doctor. Athletes who are found to be iron deficient by a physician are typically given 100 mg per day until blood tests indicate they are no longer deficient. Supplementing iron-deficient athletes with 100 to 200 mg per day of iron increased aerobic exercise performance in some,⁵ ⁶ ⁷ though not all,⁸ ⁹ double-blind studies. A recent double-blind trial found that iron-deficient women who took 20 mg per day of iron for six weeks were able to perform knee strength exercises for a longer time without muscle fatigue compared with those taking a placebo.¹⁰

Are there any side effects or interactions?

Iron (ferrous sulphate) is the leading cause of accidental poisonings in children.¹¹ ¹² ¹³ The incidence of iron poisonings in young children increased dramatically in 1986. Many of these children obtained the iron from a child-resistant container opened by themselves or another child, or left open or improperly closed by an adult.¹⁴ Deaths in children have occurred from ingesting as little as 200 mg to as much as 5.85 grams of iron.¹⁵ Keep iron-containing supplements out of a child’s reach.

Haemochromatosis, haemosiderosis, polycythaemia, and iron-loading anaemias (such as thallasaemia and sickle cell anaemia) are conditions involving excessive storage of iron. Supplementing iron can be quite dangerous for people with these diseases.

Supplemental amounts required to overcome iron deficiency can cause constipation. Sometimes switching the form of iron (see “Which forms of supplemental iron are best?” above), getting more exercise, or treating the constipation with fibre and fluids is helpful, though fibre can reduce iron absorption (see below). Sometimes the amount of iron must be reduced if constipation occurs.

Some researchers have linked excess iron levels to diabetes,¹⁶ cancer,¹⁷ increased risk of infection,¹⁸ systemic lupus erythematosus (SLE),¹⁹ exacerbation of rheumatoid arthritis,²⁰ and Huntington’s disease.²¹ The greatest concern has surrounded the possibility that excess storage of iron in the body increases the risk of heart disease.²² ²³ ²⁴ Two analyses of published studies came to different conclusions about whether iron could increase heart disease risk.²⁵ ²⁶ One trial has suggested that such a link may exist, but only in some people (possibly smokers or those with elevated cholesterol levels).²⁷ The link between excess iron and any of the diseases mentioned earlier in this paragraph has not been definitively proven. Nonetheless, too much iron causes free radical damage, which can, in theory, promote or exacerbate most of these diseases. People who are not iron deficient should generally not take iron supplements.

Patients on kidney dialysis who are given injections of iron frequently experience “oxidative stress”. This is because iron is a pro-oxidant, meaning that it interacts with oxygen molecules in ways that can damage tissues. These adverse effects of iron therapy may be counteracted by supplementation with vitamin E.²⁸

Supplementation with iron, or iron and zinc, has been found to improve vitamin A status among children at high risk for deficiency of the three nutrients. ²⁹

People with hepatitis C who have failed to respond to interferon therapy have been found to have higher amounts of iron within the liver. Moreover, reduction of iron levels by drawing blood has been shown to decrease liver injury caused by hepatitis C.³⁰ Therefore, people with hepatitis C should avoid iron supplements.

In some people, particularly those with diabetes, insulin resistance syndrome, or liver disease, a genetic susceptibility to iron overload has been reported.³¹

Many foods, beverages, and supplements have been shown to affect the absorption of iron.³²

Foods, beverages and supplements that interfere with iron absorption include

Green tea (Camellia sinensis).³³ ³⁴ ³⁵ ³⁶ This effect may be desirable for people with iron overload diseases, such as haemochromatosis. The inhibitory effect of green tea on iron absorption was 26% in one study.³⁷
Coffee (Coffea arabica, C. robusta).³⁸ ³⁹ ⁴⁰
Red wine, particularly the polyphenol component (also found in tea).⁴¹ ⁴² Since wine is also a dietary source of iron, it is not clear whether drinking red wine would lead to a deficiency of iron.
Phytate (phytic acid), found in unleavened wheat products such as matzoh, pita, and some rye crackers; in wheat germ, oats, nuts, cacao powder, vanilla extract, beans, and many other foods, and in IP-6 supplements.⁴³ ⁴⁴ ⁴⁵
Whole wheat bran, independent of its phytate content, has been shown to inhibit iron absorption.⁴⁶
Calcium from food and supplements interferes with haem-iron absorption.⁴⁷ ⁴⁸
Soya protein.⁴⁹ ⁵⁰
Eggs.⁵¹ ⁵²

Foods and supplements that increase iron absorption include

Meat, poultry, and fish.⁵³ ⁵⁴ ⁵⁵ ⁵⁶ ⁵⁷

Although vitamin C increases iron absorption,⁵⁸ ⁵⁹ ⁶⁰ ⁶¹ the effect is relatively minor.⁶²

Taking vitamin A with iron helps treat iron deficiency, since vitamin A improves the absorption and/or utilization of iron.⁶³ ⁶⁴

Although soya protein has been shown to decrease iron absorption (see above), certain soya-containing foods (e.g. tofu, miso, tempeh) have significantly improved iron absorption.⁶⁵ Some soya sauces may also enhance iron absorption.⁶⁶

Alcohol, but not red wine, has been reported to increase the absorption of ferric, but not ferrous, iron.⁶⁷ ⁶⁸

Iron has been reported to potentially interfere with manganese absorption. In one trial, women with high iron status had relatively poor absorption of manganese.⁶⁹ In another trial studying manganese/iron interactions in women, increased intake of “non-haem iron”—the kind of iron found in most supplements—decreased manganese status.⁷⁰ These interactions suggest that taking multiminerals that include manganese may protect against manganese deficiencies that might otherwise be triggered by taking isolated iron supplements.

Are there any drug interactions?
Certain medicines may interact with iron. Refer to drug interactions for a list of those medicines.

Resources

See a list of books, periodicals, and other resources for this and related topics.

*Athletes and fitness advocates may claim benefits for iron based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles on iron. For more complete and detailed information, including references and safety information, see Iron as a nutritional supplement.

References
(To view, roll mouse over heading; to hide, click on heading)

1. Mechrefe A, Wexler B, Feller E. Sports anemia and gastrointestinal bleeding in endurance athletes. Med Health R I 1997;80:216–8.

2. Clarkson PM. Micronutrients and exercise: anti-oxidants and minerals. J Sports Sci 1995;13:S11–24 [review].

3. Smith JA. Exercise, training and red blood cell turnover. Sports Med 1995;19:9–31.

4. Smith JA. Exercise, training and red blood cell turnover. Sports Med 1995;19:9–31 [review].

5. Brownlie T 4th, Utermohlen V, Hinton PS, et al. Marginal iron deficiency without anemia impairs aerobic adaptation among previously untrained women. Am J Clin Nutr 2002;75:734–42.

6. Friedmann B, Weller E, Mairbaurl H, Bartsch P. Effects of iron repletion on blood volume and performance capacity in young athletes. Med Sci Sports Exerc 2001;33:741–6.

7. Hinton PS, Giordano C, Brownlie T, Haas JD. Iron supplementation improves endurance after training in iron-depleted, nonanemic women. J Appl Physiol 2000;88:1103–11.

8. Zhu YI, Haas JD. Altered metabolic response of iron-depleted nonanemic women during a 15-km time trial. J Appl Physiol 1998;84:1768–75.

9. Nielsen P, Nachtigall D. Iron supplementation in athletes. Current recommendations. Sports Med 1998;26:207–16 [review].

10. Brutsaert TD, Hernandez-Cordero S, Rivera J, et al. Iron supplementation improves progressive fatigue resistance during dynamic knee extensor exercise in iron-depleted, nonanemic women. Am J Clin Nutr 2003;77:441–8.

11. FDA Medical Bulletin, U.S. Government Printing Office, document number 386–942/00002; February 6, 1995.

12. Nightingale SL. Action to prevent accidental iron poisoning in children. JAMA 1997;27:1343.

13. Krezenlok EP, Hoff JV. Accidental iron poisoning. A problem of marketing and labeling. Pediatrics 1979;63:591–6.

14. Morris CC. Pediatric iron poisonings in the United States. South Med J 2000;93:352–8.

15. Mills KC, Curry SC. Acute iron poisoning. Emerg Med Clin N Am 1994;12;397–413.

16. Cutler P. Deferoxamine therapy in high-ferritin diabetes. Diabetes 1989;38:1207–10.

17. Stevens RG, Graubard BI, Micozzi MS, et al. Moderate elevation of body iron level and increased risk of cancer occurrence and death. Int J Cancer 1994;56:364–9.

18. Weinberg ED. Iron withholding: a defense against infection and neoplasia. Am J Physiol 1984;64:65–102.

19. Oh VMS. Iron dextran and systemic lupus erythematosus. Br Med J 1992;305:1000 [letter].

20. Dabbagh AJ, Trenam CW, Morris CJ, Blake DR. Iron in joint inflammation. Ann Rheum Dis 1993;52:67–73.

21. Bartzokis G, Cummings J, Perlman S, et al. Increased basal ganglia iron levels in Huntington disease. Arch Neurol 1999;56:569–74.

22. Salonen JT, Nyyssonen K, Korpela H, et al. High stored iron levels associated with excess risk of myocardial infarction in western Finnish men. Circulation 1992;86:803–11.

23. Kechl S, Willeit J, Egger G, et al. Body iron stores and the risk of carotid atherosclerosis. Circulation 1997;96:3300–7.

24. Tzonou A, Lagiou P, Trichopoulou A, et al. Dietary iron and coronary heart disease risk: a study from Greece. Am J Epidemiol 1998;147:161–6.

25. Danesh J, Appleby P. Coronary heart disease and iron status. Meta-analyses of prospective studies. Circulation 1999;99:852–4.

26. de Valk B, Marx MMJ. Iron, atherosclerosis, and ischemic heart disease. Arch Intern Med 1999;159:1542–8 [review].

27. Klipstein-Grobusch K, Koster JF, Grobbee DE, et al. Serum ferritin and risk of myocardial infarction in the elderly: the Rotterdam Study. Am J Clin Nutr 1999;69:1231–6.

28. Roob JM, Khoschsorur G, Tiran A, et al. Vitamin E attenuates oxidative stress induced by intravenous iron in patients on hemodialysis. J Am Soc Nephrol 2000;11:539–49.

29. Muñoz EC, Rosado JL, Lopez P, et al. Iron and zinc supplementation improves indicators of vitamin A status of Mexican preschoolers. Am J Clin Nutr 2000;71:789–94.

30. Di Bisceglie AM, Bonkovsky HL, Chopra S, et al. Iron reduction as an adjuvant to interferon therapy in patients with chronic hepatitis C who have previously not responded to interferon: a multicenter, prospective, randomized, controlled trial. Hepatology 2000;32:135–8.

31. Ferrennini E. Insulin resistance, iron, and the liver. Lancet 2000;355:2181–2 [letter].

32. Hallberg L, Hulthen L. Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability of dietary iron. Am J Clin Nutr 2000;71:1147–60.

33. Disler PB, Lynch SR, Charlton RW, et al. The effect of tea on iron absorption. Gut 1975;16:193–200.

34. Derman D, Sayers M, Lynch SR, et al. Iron absorption from a cereal-based meal containing cane sugar fortified with ascorbic acid. Br J Nutr 1977;38:261–9.

35. Hallberg L, Rossander L. Effect of different drinks on the absorption of non-heme iron from composite meals. Hum Nutr Appl Nutr 1982;36:116–23.

36. Kaltwasser JP, Werner E, Schalk K, et al. Clinical trial on the effect of regular tea drinking on iron accumulation in genetic haemochromatosis. Gut 1998;43:699–704.

37. Samman S, Sandstrom B, Toft MB, et al. Green tea or rosemary extract added to foods reduces nonheme-iron absorption. Am J Clin Nutr 2001;73:607–12.

38. Derman D, Sayers M, Lynch SR, et al. Iron absorption from a cereal-based meal containing cane sugar fortified with ascorbic acid. Br J Nutr 1977;38:261–9.

39. Hallberg L, Rossander L. Effect of different drinks on the absorption of non-heme iron from composite meals. Hum Nutr Appl Nutr 1982;36:116–23.

40. Morck TA, Lynch SR, Cook JD. Inhibition of food iron absorption by coffee. Am J Clin Nutr 1983;37:416–20.

41. Bezwoda WR, Torrance JD, Bothwell TH, et al. Iron absorption from red and white wines. Scand J Haematol 1985;34:121–7.

42. Cook JD, Reddy MB, Hurrell RF. The effect of red and white wines on nonheme-iron absorption in humans. Am J Clin Nutr 1995;61:800–4.

43. Hallberg L, Hulthen L. Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability of dietary iron. Am J Clin Nutr 2000;71:1147–60.

44. Sandberg AS, Brune M, Carlsson NG, et al. Inositol phosphates with different numbers of phosphate groups influence iron absorption in humans. Am J Clin Nutr 1999;70:240–6.

45. Hallberg L, Brune M, Rossander L. Iron absorption in man: ascorbic acid and dose-dependent inhibition by phytate. Am J Clin Nutr 1989;49:140–4.

46. Simpson KM, Morris ER, Cook JD. The inhibitory effect of bran on iron absorption. Am J Clin Nutr 1981;34:1469–78.

47. Hallberg L, Brune M, Erlandsson M, et al. Calcium: effect of different amounts on nonheme- and heme-iron absorption in humans. Am J Clin Nutr 1991;53:112–9.

48. Hallberg L, Rossander-Hulthén L, Brune M, Gleerup A. Inhibition of haem-iron absorption in man by calcium. Br J Nutr 1992;69:533–40.

49. Cook JD, Morck TA, Lynch SR. The inhibitory effect of soy products on nonheme iron absorption in man. Am J Clin Nutr 1981;34:2622–9.

50. Hallberg L, Rossander L. Effect of soy protein on nonheme iron absorption in man. Am J Clin Nutr 1982;36:514–20.

51. Cook JD, Monsen ER. Food iron absorption in human subjects. III. Comparison of the effect of animal proteins on nonheme iron absorption. Am J Clin Nutr 1976;29:859–67.

52. Rossander L, Hallberg L, Bjorn-Rasmussen E. Absorption of iron from breakfast meals. Am J Clin Nutr 1979;32:2484–9.

53. Hallberg L. Bioavailability of dietary iron in man. Annu Rev Nutr 1981;1:123–47 [review].

54. Layrisse M, Martinez-Torres C, Roche M. Effect of interaction of various foods on iron absorption. Am J Clin Nutr 1968;21:1175–83.

55. Cook JD, Monsen ER. Food iron absorption in human subjects. III. Comparison of the effect of animal proteins on nonheme iron absorption. Am J Clin Nutr 1976;29:859–67.

56. Bjorn-Rasmussen E, Hallberg L. Effect of animal proteins on the absorption of food iron in man. Nutr Metab 1979;23:192–202.

57. Hallberg L, Rossander L. Improvement of iron nutrition in developing countries: comparison of adding meat, soy protein, ascorbic acid, citric acid, and ferrous sulphate on iron absorption from a simple Latin American-type of meal. Am J Clin Nutr 1984;39:577–83.

58. 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;59:1381–5.

59. Hallberg L, Brune M, Rossander L. The role of vitamin C in iron absorption. Int J Vitam Nutr Res Suppl 1989;30:103–8.

60. Lynch SR, Cook JD. Interaction of vitamin C and iron. Ann N Y Acad Sci 1980;355:32–44.

61. Hallberg L, Brune M, Rossander L. Effect of ascorbic acid on iron absorption from different types of meals. Studies with ascorbic-acid-rich foods and synthetic ascorbic acid given in different amounts with different meals. Hum Nutr Appl Nutr 1986;40:97–113.

62. 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;59:1381–5.

63. Suharno D, West CE, Muhilal, et al. Supplementation with vitamin A and iron for nutritional anemia in pregnant women in West Java, Indonesia. Lancet 1993;342:1325–8.

64. Semba RD, Muhilal, West KP Jr, et al. Impact of vitamin A supplementation on hematological indicators of iron metabolism and protein status in children. Nutr Res 1992;12:469–78.

65. Macfarlane BJ, van der Riet WB, Bothwell TH, et al. Effect of traditional oriental soy products on iron absorption. Am J Clin Nutr 1990;51:873–80.

66. Baynes RD, Macfarlane BJ, Bothwell TH, et al. The promotive effect of soy sauce on iron absorption in human subjects. Eur J Clin Nutr 1990;44:419–24.

67. Charlton RW, Jacobs P, Seftel H, Bothwell TH. Effect of alcohol on iron absorption. Br Med J 1964;5422:1427–9.

68. Hallberg L, Rossander L. Effect of different drinks on the absorption of non-heme iron from composite meals. Hum Nutr Appl Nutr 1982;36:116–23.

69. Finley JW. Manganese absorption and retention by young women is associated with serum ferritin concentration. Am J Clin Nutr 1999;70:37–43.

70. Davis CD, Malecki EA, Gerger JL. Interactions among dietary manganese, heme iron, and nonheme iron in women. Am J Clin Nutr 1992;56:926–32.

Learn more about Healthnotes, the company.

Learn more about the authors of Healthnotes.

The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2007.