Featured Nutrient: Zinc

Complain of a head cold and stuffy nose and chances are some well-intentioned acquaintance will suggest a zinc lozenge, the very supplement that male would-be swingers were popping in the '70s to increase bedroom stamina. For a trace mineral, needed in only tiny amounts, zinc has garnered a lot of attention in recent years. Much of it is well deserved, although surprisingly not for the reasons many suspect.

What it does:

Zinc is integral to almost every cell of the human body, it keeps the immune system healthy, helps heal wounds, aids in breaking down carbohydrates, fats and proteins, maintains the body's keen sense of both taste and smell, regulates testosterone and supports the body in growing and developing properly. In addition, scientists continue to investigate the role that zinc may play in preventing prostate cancer and diabetes, in regulating male fertility and in warding off macular degeneration—an age-related condition that can lead to blindness. As for preventing the common cold and enhancing sexual prowess, current research suggests that any benefit may stem more from a placebo effect than a true remedy, although the jury is still out on whether zinc can help shorten the duration of a cold. Health professionals are quick to warn, however, that people can easily harm themselves by taking too much supplemental zinc.

Although zinc is readily available through diet, about 20 percent of men and 40 percent of women in this country fail to get enough. True zinc deficiencies are rare in the United States, but health researchers are finding that low levels have a multitude of consequences: difficulty healing wounds, diminished appetite, low birth weight, possible infertility in men, muscle fatigue and diminished strength.

One study recently showed that young men's muscle strength and endurance dropped when they ate a low-zinc diet (4 milligrams/day) for 9 weeks, compared to a similar time period when they consumed a higher-zinc diet (15 mg/day). According to the researcher, Hank Lukaski, a physiologist at the USDA Human Nutrition Research Center in Grand Forks, North Dakota, zinc activates an enzyme that helps the body shed carbon dioxide, which is produced when we burn carbohydrates and fat. A buildup of carbon dioxide will cause the cells to malfunction, and make even simple physical chores more difficult. "We're talking about normal activities, nothing more than someone carrying two shopping bags out of the grocery store," Lukaski says.

How much you need:

As essential as zinc is, you don't need much for a healthy body. The recommended dietary intake for men is 11 mg/day, for women 8 mg/day (11 and 12 mg, respectively, if pregnant or lactating). Adolescents and the elderly are two populations at risk of getting too little zinc. Strict vegans, who don't eat meat, dairy or eggs, should also keep an eye on their zinc intake.

But unless you have a health condition that warrants zinc supplementation, most health professionals advise against it. While a balanced vitamin/mineral supplement is fine, too much zinc, near the upper limit of 40 mg/day and above, may affect the body's ability to absorb and store calcium and copper, and may eventually lead to a debilitating anemia.

Food Sources of zinc:

It's easy to enter the danger zone with supplemented zinc, so dietitians encourage most people to depend on diet instead. Oysters offer a particularly rich source, but lean red meats and chicken, along with legumes, whole grains and dairy products, also pack a tidy sum.

Oysters, steamed (3 oz.) = 30.0 mg

Cooked beef tenderloin (3 oz.) = 4.8 mg

Turkey, dark meat, roasted (3 oz.) = 3.9 mg

Chickpeas (7 oz.) = 2.8 mg

Roast chicken leg = 2.7 mg

Pumpkin seeds (1/4 cup) = 2.6 mg

Cooked pork tenderloin (3 oz.) = 2.5 mg

Plain low-fat yogurt (1 cup) = 2.2 mg

Wheat germ (2 Tbsp.) = 1.8 mg

Tofu (4 oz.) = 1.7 mg

Dry roasted cashews (1 oz.) = 1.6 mg

Swiss cheese (1 oz.) = 1.0 mg