Vitamins, Minerals and Dietary Supplements
What is Zinc?
Zinc is an important trace mineral. A bluish-white, metallic element, it is second only to iron in terms of its concentration in the body.
Why do we need it?
Zinc plays an important role in the proper functioning of the body's immune system. Several studies have shown that zinc lozenges shorten the duration of cold symptoms in adults.
Zinc is required for a number of activities related to cell reproduction and wound healing. It has also been linked to improvements in one's senses of smell and taste, and is involved in the body's ability to metabolize carbohydrates for energy consumption.
How much should I take?
According to the National Academy of Sciences, the recommended daily allowance (RDA) for zinc is as follows:
- Adult men: 15 milligrams/day
- Adult women: 12 milligrams/day
- Children (7-10 years): 10 milligrams/day
- Infants: 5 milligrams/day
- Pregnant and lactating women: 19 milligrams/day
Higher levels of zinc are usually reserved for treating certain health conditions. Such supplementation should take place only under the supervision of a health care professional.
What are some good sources of zinc?
High-protein foods such as chicken, beef, eggs and tofu contain high amounts of zinc. The dark meat of a chicken has a higher zinc content than the light meat. Other good sources include peanuts, peanut butter and legumes (such as beans, peas and lentils).
What can happen if I don't get enough zinc?
Symptoms associated with zinc deficiency include slow or impaired growth, decreased resistance to infections, slower wound healing and loss of hair. The senses of smell and taste can also be impaired by low zinc levels.
What can happen if I take too much?
Taking large amounts of zinc supplements (70 or more times the recommended daily allowance) may cause diarrhea, nausea, abdominal cramps and vomiting within 3-10 hours after taking the supplements. These symptoms can be reversed or diminished by discontinuing supplement use.
It should also be known that zinc inhibits copper absorption, which can lead in some cases to anemia and lower levels of HDL ("good") cholesterol. Fortunately, most zinc supplements also contain extra amounts of copper to prevent inhibition from occurring.
- National Academy of Sciences. Recommended Daily Allowances, 10th ed., 1989.
- Macknin ML, Piedmonte M, Calendine C, et al. Zinc gluconate lozenges for treating the common cold in children. A randomized controlled trial. JAMA 1998;279:1962-67.
- Prasad A. Discovery of human zinc deficiency and studies in an experimental human model. Am J Clin Nutr 1991;53:403-12 [review].
- Prasad AS. Zinc in human health: an update. J Trace Elements Exper Med 1998;11:63-87.
- Sandstead HH. Requirements and toxicity of essential trace elements, illustrated by zinc and copper. Am J Clin Nutr 1995;61(suppl):621S-24S [review].