Zinc and Magnesium Deficiency Problems

Zinc and magnesium are critical for athletes, but deficiencies are prevalent, primarily because it is difficult to get the proper amounts—12 mg/day zinc for adults, 280 mg/day magnesium for women, 350 mg/day magnesium for men—through diet alone.¹ USDA studies reveal that 68 percent of self-selected diets in the general population contain less than two-thirds of the RDA for zinc, ² and 39 percent contain less than two-thirds of the RDA for magnesium.³

Although many foods contain zinc, magnesium, and vitamin B6 athletes rarely take in sufficient quantities. One reason may be that foods rich in these minerals—oysters and beef liver—are not diet staples.

Do athletes get sufficient zinc, magnesium, or vitamin B6 from their multiple vitamin/mineral supplements? In a study conducted at the department of physiology and applied nutrition at the Australian Institute of Sport, blood indicators of eight vitamins (A, B1, B2, B6, B12, C, E, and folate) and five minerals (calcium, copper, magnesium, phosphorus, and zinc) were measured in 86 athletes before and after a seven- to eight-month training period.⁴ During this time, half consumed a multivitamin/mineral supplement and a matched group took placebo. Afterwards, blood indicators of vitamins B1, B6, B12, and folate increased—but there were no effects on blood-mineral levels. These minerals may not have been absorbed because of competitive and antagonistic interactions. For example, zinc and magnesium are poorly absorbed when taken with calcium-containing foods or supplements. So why are combination calcium-magnesium supplements sold? Probably because they are both poorly absorbed and formulators are trying to increase their uptake by the body.

Research indicates that zinc deficiency in athletes can result in decreased blood levels of testosterone and IGF-1 (insulinlike growth factor), increased serum estrogen levels, and compromised androgen receptor activity.⁵ It is important to activate androgen receptors because they promote testosterone effectiveness.

—E.B.

References

1. Singh A, et al. Magnesium, zinc, and copper status of U.S. Navy SEAL trainees. Am J Clin Nutr 1989;49(4):695-700.

2. Holden J, et al. Zinc and copper in self-selected diets. J Am Diet Assoc 1979;75(1):23-8.

3. Morgan K, et al. Magnesium and calcium dietary intakes of the U.S. population. J Am Coll Nutr 1985;4(2):195-206.

4. Telfor R, et al. The effect of 7 to 8 months of vitamin/mineral supplementation on the vitamin and mineral status in athletes. Int J Sports Nutr 1992;2(2):123-34.

5. Brun J, et al. Serum zinc in highly trained adolescent gymnasts. Bio Trace Elem Res 1995;47:273-8.