Scan a list of the health problems associated with poor zinc intake, and you’ll get an immediate sense of this essential mineral’s wide and varied roles in the body. When children lack zinc in their diets, researchers have found, they tend to grow more slowly than normal, and their sexual maturity is delayed. Zinc deprivation has also been linked to poor appetite, decreased resistance to infection, slow wound healing, infertility, and low hormone levels, especially in men. Some people with zinc deficiency experience hair loss, skin and nail problems, taste and smell difficulties, night blindness, and ulcers on the surface of the eyes, among other ailments.
The deficiency doesn’t have to be drastic for some of these problems to appear. "The body’s immune system seems particularly sensitive to zinc status," says Philip Reeves, Ph.D., research chemist with the U.S. Department of Agriculture Human Nutrition Research Center in Grand Forks, North Dakota. "Even a mild deficiency can cause immunity problems, and a severe deficiency can have devastating effects."
Zinc is needed by more than 300 enzymes, the spark plugs that get chemical reactions going in our bodies. It’s found in every organ and every tissue—anyplace there is protein—because it is needed for the process of making protein.
Producing Protein
Since protein is needed to make tissues such as skin and muscles, it’s no surprise that a zinc shortage leads to slow wound healing, skin breakdown, or muscle loss. Additionally, it is used for immune cells that fight infection; hormones that regulate growth, appetite, and sex drive; neurotransmitters that allow our various body parts to communicate with one another; and even the pigments in the backs of our eyes that allow us to see.
Zinc’s role in protein processing is varied. In some cases, proteins called zinc fingers reach out and grab specific parts of DNA so that it can begin the process of making other proteins. Zinc also helps to retrieve and copy the "recipe"—the amino acid sequence—for a particular protein from the cell’s genetic material.
Zinc also participates when a cell needs to produce a copy of its genes as it prepares to divide. "Some enzymes that string together the bits that make up the long chains of DNA and RNA are zinc-dependent," Dr. Reeves says. "When these enzymes don’t work correctly, a cell’s genetic material isn’t made." When there’s a lack of genetic material, he points out, there’s a general slowdown in growth and tissue maintenance because new cells aren’t being produced. There is a drop-off in the production of immune system cells and a breakdown in muscle and skin tissue.
SUPPLEMENTSNAPSHOT
| Zinc May help: Macular degeneration, cataracts, male infertility associated with low hormone levels, hair loss, wound healing, impotence, prostate problems, dermatitis, canker sores, bedsores, loss of appetite, low immunity, taste and smell problems, genital herpes, binge-eating disorder, osteoarthritis, HIV, and inflammatory conditions such as lupus and rheumatoid arthritis. Zinc throat lozenges may help treat colds. Daily Value: 15 milligrams. Special instructions: Take with food to reduce stomach irritation, but avoid taking with a lot of high-fiber foods, since fiber interferes with absorption. Calcium also interferes, so if your calcium intake from food and supplements is 1,200 milligrams daily, you should take 18 milligrams or more of zinc every day. Absorption can also be compromised by large amounts of iron; for best results, do not get more than 30 milligrams of iron daily from food and supplements. Since large amounts of zinc impair copper absorption, get 1 milligram of copper for every 10 milligrams of zinc. Who’s at risk for deficiency: Pregnant women, infants, elderly people who don’t eat well, vegetarians, people with diabetes, and alcoholics. Good food sources: Cooked oysters, clams, crab, red meat, poultry, fish, and beans. Cautions and possible side effects: Do not take more than 20 milligrams a day of zinc (and no more than 2 milligrams a day of copper) unless directed by your physician. |
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.
Large amounts of iron can interfere with your ability to absorb zinc, so if you are taking supplemental iron to correct iron-deficiency anemia, you should take it separately from any zinc supplements, Dr. Hunt says.
