Zinc

Antioxidant Protection

Zinc is needed to make an important antioxidant enzyme called zinc-copper superoxide dismutase. Like vitamins E and C—other antioxidants that your body needs—this enzyme helps neutralize free radicals, the free-roaming, unstable molecules that can cause a chain reaction of damage throughout your body. "Superoxide dismutase is found in every cell in the body, but it’s especially concentrated in the liver and kidneys, where it helps to neutralize toxins before they have a chance to cause problems," Dr. Reeves says.

Your lungs also get the support of this enzyme, which they need because they’re constantly exposed to potentially damaging oxygen. Your eyes, too, get some protection from superoxide dismutase, as it helps shield them from the effects of ultraviolet light.

Zinc also helps to stabilize the structure of cell membranes, says Dr. Reeves. That’s an important role because the membranes that surround cells act as a kind of security system. When they are intact and working right, they help to carefully regulate what goes in and out of a cell. Needed nutrients go in, and wastes go out.

"Zinc-dependent enzymes help to protect both proteins and fats in the membrane from being damaged by oxygen," Dr. Reeves observes.

If a cell’s normally fluidlike membrane is damaged, though, it becomes rigid, interfering with the necessary flow of nutrients and wastes into and out of the cell. Specific receptor sites and transport systems—a cell’s loading platforms—don’t work. "The receptor sites for insulin, for instance, are one type that may be protected by zinc," Dr. Reeves says.

Are You Getting Enough?

Our bodies try to conserve zinc if we’re not eating much, and we absorb more zinc from foods when it’s available. "The absence of evidence of deficiency suggests that most people in the United States do get enough zinc, even if they’re not always getting the Daily Value," says Janet Hunt, R.D., Ph.D., also with the USDA research center in North Dakota. In the United States, people average about 10 milligrams a day of zinc, two-thirds of the Daily Value of 15 milligrams. Most of that comes from meat, fish, and poultry.

So who’s most likely to be short on zinc? Vegetarians who aren’t getting enough good nonmeat sources of zinc, such as beans; older people who simply aren’t eating enough food; and people on diets that shortchange them on numerous nutrients. Severe zinc deficiency is also a well-known complication of alcohol abuse.

If you’re taking a zinc supplement, you don’t need to worry about the form of zinc in the tablet, Dr. Hunt says. Most commercial forms are readily absorbed and utilized.

Mingling Your Metals

Zinc can interfere with copper absorption at amounts as low as 20 milligrams a day, so you should get 1 milligram of copper for every 10 milligrams of zinc that you take in through diet or supplements. Most people don’t need to take more than 15 milligrams of supplemental zinc and 1.5 milligrams of copper a day, Dr. Hunt says. These amounts of zinc and copper are available in many multivitamin/mineral supplements.