Zinc is an essential trace element found in every cell of the human body.
What does it do?
Zinc plays many diverse roles in enabling healthy growth and development and in promoting good health in general. The body needs it to:
- enable the activity of more than 200 biological enzymes
- help manufacture proteins and genetic material
- achieve normal growth and skeletal development
- stimulate hair growth
- develop taste perception
- assist in hormonal activity, reproduction and lactation
- carry out immune functions, such as protecting against infection and cancer
As you might surmise from this list, a deficiency of zinc can result in problems such as poor growth, difficulty in wound healing, loss of appetite, undesirable skin changes, and adverse effects on immune-system components.
Where do you get it?
Most of the zinc in the typical U.S. diet comes from animal products, such as:
- seafood (especially oysters)
Zinc is also available from other food sources, such as legumes, whole-grain cereals, wheat germ and nuts. However, as explained in the following section, zinc from these sources may not be absorbed as well as zinc from animal products.
How much do we need?
The Recommended Dietary Allowance (RDA) for zinc is 15 milligrams per day for men and 12 milligrams per day for women. For women who take large amounts of calcium (1400 milligrams) every day, 18 milligrams a day may be recommended.
Since the typical U.S. diet provides about 10 to 15 milligrams of zinc per day, the average man or woman will consume the recommended amount. However, because animal products are the major sources of zinc, vegetarians may not get adequate amounts of this important trace element. This may apply in particular to vegetarian women who restrict their caloric intake as was as their animal-product consumption.
One very important thing to understand is that the amount of zinc you consume is not the only factor that affects whether you are getting enough zinc. You also must take into account the amount that your body actually absorbs. Here are some of the factors that affect the body's ability to absorb zinc.
- Women who take large amounts of calcium (more than 1,400 milligrams a day) have lower zinc absorption than women who do not.
- People with good zinc status will not absorb zinc as efficiently as people with poor zinc status.
- Large amounts of zinc are not absorbed as well as small amounts are.
- Iron in large amounts can inhibit the absorption of zinc.
- Zinc from non-animal sources (legumes, whole-grain cereals, wheat germ and nuts) may not be absorbed as well as zinc from animal products.
- High concentrations of fiber and phytate in the diet may be responsible for lower zinc absorption, but this generally does not pose a problem in the U.S.
Is it safe?
Taking more than 100 milligrams of zinc per day can be dangerous. With zinc gluconate now being promoted as a means of warding off colds, it is especially important to be aware of the risks of taking too much zinc.
- Ironically, too much zinc, like too little zinc, can depress the immune system.
- Excessive zinc can cause anemia, copper deficiencies and lowered levels of good cholesterol
(HDL) in the blood.
- Taking more than the recommended dosage of zinc gluconate in hopes of warding off a cold is ill-advised.
- Using zinc gluconate on a long-term basis is not recommended.
- The effectiveness of 13-milligram zinc gluconate lozenges in preventing colds has been questioned.