Excerpted from: Nancy Clark MS, RD, THE PHYSICIAN AND SPORTSMEDICINE - VOL 24 - NO. 6 - JUNE 96
In the quest to eat right, don't overlook minerals - they're an important part of your diet. If you are active, you may be considering taking some of the popular supplements - iron, zinc, chromium, and selenium. But just what are these minerals?
Minerals are often referred to as trace elements because humans need only small amounts of them. There are specific recommended dietary allowances (RDAs) for iron and zinc. But because less is known about chromium and selenium, there are only "safe and adequate" daily ranges for them. The low end of the range prevents deficiencies that can impair your body's function; the high end of the range is below toxic (poisonous) doses.
People who take mineral supplements do so to optimize their health. But if you are taking a mineral supplement, keep in mind that over-supplementing may lead to a mineral imbalance or toxicity. The theory "if a little bit is good, more must be better" doesn't work for mineral supplements because more of one mineral may keep your body from absorbing another mineral. Exceeding the RDA is not recommended.
Iron is a part of red blood cells and helps transport oxygen to exercising muscles. If you have low levels of iron and become anaemic, your muscles will receive less oxygen and produce more lactic acid. A build-up of lactic acid results in premature fatigue when you work out. Anaemia is more common among women than men because women tend to lose iron through menstrual bleeding.
The RDA for iron is 10 mg for men and 15 mg for women.
Zinc is in every tissue throughout your body and is an important component in energy metabolism (using food for energy). Zinc is essential for making protein, which means it helps grow muscles and other tissues. It can also aid in injury healing and immunity against diseases. If you have a zinc deficiency, you may have rough, dry skin and you may lose your appetite and your ability to taste foods. The RDA for zinc is 12 mg per day for women and 15 mg for men. This is the amount commonly added to multivitamin and mineral supplements. Vegetarians tend to have lower zinc levels than do meat eaters. So if you don't eat meat, taking a zinc supplement may make sense to help guard against a deficiency.
Be careful to avoid the “more is better” rule here, as studies have shown that zinc supplements in large doses (between 50 mg to 100 mg) might have adverse consequences, such as altered copper and iron status, impaired immune function, and a decline in "good" cholesterol.
Chromium is an essential mineral that you need in small amounts to maintain normal blood sugar balance. The reference daily intake (which is a new type of guideline similar to the RDA) for chromium is 120 micrograms per day for men and women. Be aware that excess chromium interacts with iron and zinc, so you should keep your total intake under 200 micrograms per day.
If you have diabetes and are deficient in chromium, supplementation may help you control your blood sugar. Although chromium deficiency is not the primary cause of diabetes in the United States, if you have a family history of late-onset (type II) diabetes, supplementation may be beneficial.
Selenium is a powerful antioxidant that works together with vitamin E. Antioxidants are compounds that protect you from oxygen particles that cause cell damage that in turn can lead to cancer and other diseases. The RDA for selenium is 55 micrograms for women and 70 micrograms for men. Because intakes greater than 200 micrograms may be toxic, the best advice to date is to limit selenium intake to the RDA.
Remember, if you are not getting adequate amounts of minerals from your diet, you may want to consider supplementing… Mind your Minerals!