Featured Nutrient: Vitamin C

Vitamin C burst into prominence back in the 1970s, when Nobel Prize-winning scientist Linus Pauling claimed that high doses could stop cancer and might be the long-sought cure for the common cold.

Alas, neither claim has quite held up under scrutiny. Vitamin C doesn't prevent colds. Nor does taking large doses slow or stop cancer. But Pauling's instincts were not entirely wrong. There are still many sound reasons to get plenty of C.

What it does:

Researchers have long known that vitamin C is an essential building block of collagen, the structural material for bone, skin, blood vessels and other tissue. Failing to get enough vitamin C causes inflammation of the gums, scaly skin, nosebleed, painful joints and other problems associated with scurvy.

In addition, many studies show that eating foods rich in C can reduce the risk of developing cancer, particularly cancers that strike the mouth and digestive tract, according to Jane Higdon, a nutrition scientist at the Linus Pauling Institute at Oregon State University. Vitamin C is a potent antioxidant, able to neutralize unstable oxygen molecules that might otherwise damage DNA. Recent findings suggest it may also protect against Helicobacter pylori, bacteria linked to both stomach cancer and ulcers. A 2003 study at the San Francisco Veterans Affairs Medical Center reported that people with high blood levels of vitamin C are less likely to test positive for infection by H. pylori. The vitamin appears to inhibit bacterial growth.

Vitamin C is also proving to be friendly to the heart and arteries. Analyzing data from more than 85,000 women in the Nurses Health Study, researchers at Children's Hospital, Boston, reported in 2003 that those with the highest intake of C had the lowest risk of heart disease over a 16-year period. Here, too, the antioxidant effect may be at work, preventing damage to artery walls that can promote cholesterol buildup. But vitamin C seems to protect in other ways as well. In 2004, scientists from the University of Oslo reported that after volunteers ate two or three vitamin-C-rich kiwis a day for 28 days, platelets in their blood were less likely to clump together and form small blood clots that can jam arteries and lead to heart attack or stroke. Eating kiwis also lowered triglycerides, or fats in the blood, by 15 percent, an effect that scientists credit to kiwis' vitamin C, E and polyphenol content.

Getting plenty of C may be especially important for pregnant moms and infants. Last year a study in Seoul, South Korea, reported higher birth weights among babies born to mothers with high vitamin C levels. This year a report in the European Journal of Clinical Nutrition suggests that vitamin C in breast milk may reduce the risk of allergic dermatitis in predisposed infants.

How much you need:

The current recommended daily intake for men is 90 mg and for women it is 75 mg. "Don't waste your money on megadoses of vitamin C," says Higdon. A National Institutes of Health study showed that the body can only absorb a maximum of about 400 milligrams a day; more than that simply washes out of the system (the upper tolerable limit for vitamin C has been set at 2,000 milligrams per day). Follow the latest advice to eat between five and nine servings of fruits and vegetables a day and chances are you'll get all you need—especially if you choose several foods high in C.

Food Sources of Vitamin C:

Virtually everything in the produce section boasts some vitamin C. Excellent sources (per 1/2 cup serving) include:

green bell pepper = 60 mg

orange = 48 mg

strawberries = 45 mg

broccoli = 39 mg

cantaloupe = 29 mg

tomato = 23 mg

turnip greens, cooked = 20 mg

sweet potato, baked with skin = 20 mg

okra, cooked = 13 mg