Requirements: The RDA for zinc in adults is 15 mg., with additional amounts needed during pregnancy and lactation. Yet the average diet contains only about 10 mg. of zinc. And when zinc needs are considered, we likely need even more than 15 mg. per day to be sure we are meeting our requirements. Adequate amounts can be met by a good diet, especially with good protein and calorie intake. Vegetarians can eat more whole grains; even with some of the zinc binding to grain phytate, we still get a fair share into our body from these zinc-rich foods. Since absorption is about 30-40 percent, our total zinc body tissue needs are about 4-6 mg. per day.

We probably need 15-30 mg. of available (elemental) zinc daily for maintenance and probably about 30-60 mg. for treatment, though more is sometimes used. Fifteen mg. of zinc is often included in general supplement formulas. Separately, zinc gluconate and sulfate in reasonable amounts are used commonly without any side effects, though zinc gluconate is usually a little better tolerated than zinc sulfate. The amino-acid-chelated zinc is probably the best tolerated and absorbed though it is more expensive. Zinc sulfate tablets or capsules of 220 mg. provide 55 mg. of elemental zinc. A supplement labeled "zinc 25 mg. as gluconate" should provide 25 mg. elemental zinc. In medical treatment or research, zinc sulfate 220 mg. may be used two to three times daily, supplying about 100-150 mg. of available zinc for absorption. This dosage is usually tolerated fairly well.

Although 30-60 mg. of elemental zinc per day is the usual therapeutic level, more may be needed to correct zinc deficiency. Taking zinc alone two hours after meals or first thing in the morning will increase absorption by reducing the competition with other nutrients, such as calcium and copper, or food constituents such as the phytates and fibers in grains. With infections, burns, before or after surgery, in pregnancy, or with aging (often accompanied with lower absorption), 50-75 mg. per day is suggested as a therapeutic dose.

When taking higher amounts of zinc, we must make sure we get adequate amounts of copper-at least 2-3 mg. supplemented, and possibly more with higher zinc intakes-so copper deficiency does not occur. The suggested zinc to copper ratio is about 15:1. About 200 mcg. per day of selenium should also be taken, to prevent depletion by supplemental zinc. Zinc may be taken with magnesium, vitamin C, and B complex vitamins, but it is best to take a regular vitamin-mineral combination with 15-30 mg. of zinc in proper proportion to other minerals, so that deficiencies of zinc or imbalances of the other minerals do not occur.