Regular meals will provide enough zinc


February 18, 1992|By Colleen Pierre, R.D. | Colleen Pierre, R.D.,Contributing Writer

Belly up to the bar -- the raw bar, that is.

Six raw oysters contain enough zinc to rev up your immune system and improve your health.

But beware of zinc supplements. Too much of a good thing can have exactly the opposite effect.

Zinc is a mineral your body needs in relatively small amounts. The National Research Council suggests 15 milligrams a day for men and 12 milligrams a day for women generously covers the needs of all healthy people, even strict vegetarians whose food choices contain zinc that is not easily absorbed by the body.

Most Americans get their zinc from meat: 3-ounce portions of lean beef provide 5 milligrams; lean pork, 3 milligrams; liver, 4 milligrams; chicken breast, 0.85 milligrams; chicken thigh, 2 milligrams; turkey (mixed light and dark), 3 milligrams.

On the grain side, 1 cup of cooked oatmeal offers 1 milligram; barley, 1 milligram; and bulgur wheat, 3 milligrams.

A 1984 survey of U.S. foods found that it took a 2,850-calorie diet to provide 13 milligrams of zinc.

Even marginal zinc deficiency results in loss of appetite, retarded growth in children, depression of the immune system, delayed wound healing and loss of taste sensation.

In addition, a 1988 study showed that zinc supplements slowed the rate of visual loss for people with macular degeneration.

So, should you start popping zinc? Not really.

First, zinc is subject to strong homeostatic regulation. That means no matter how much you consume, whether in food or supplements, your body adjusts its absorption rate based on a lot of other factors.

Also, the small amounts found in food are absorbed more efficiently than the large amounts from supplements.

And, when zinc stores are low, you absorb more. A well-balanced diet provides enough zinc.

On the other hand, overdosing on zinc is relatively easy to do, but hard to detect.

A large overdose, 2,000 milligrams or more a day, is easy to spot. It produces gastrointestinal irritation and vomiting.

But small overdoses of 18.5 milligrams and 25 milligrams per day over a period of time produce no symptoms, yet have been shown to interfere with copper absorption.

Mid-sized overdoses can produce anemia and bleeding in the stomach, as well as reducing HDL (good) cholesterol, increasing risk for heart disease.

Recent advertising encourages supplementation, often at levels of 40 milligrams a day or more. And daily overdosing eventually leads to toxicity.

If you're taking a supplement, check the label. Be sure you're getting no more than 100 percent of the RDA for zinc, 15 milligrams.

Getting your zinc from food is different.

You get varying amounts each day, and a big day once in a while helps your daily average.

So, if you're hungry, belly up to the raw bar. Six medium oysters provide 34 milligrams of zinc.

Colleen Pierre, a registered dietitian, is the nutrition consultant to the Union Memorial Sports Medicine Center in Baltimore and director of Eating Together in Baltimore

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