Diet File: Vitamin C

Why you need it:
Vitamin C helps repair wounds and strengthen blood vessels, is vital for healthy teeth and gums, and may even boost your immune system. This important antioxidant also helps protect against heart disease, certain cancers, cataracts, and macular degeneration, a disorder that causes gradual loss of vision in older adults. Vitamin C is also linked to a decreased risk of osteoporosis, possibly because it helps form collagen, a protein that supports healthy bones. Yet another health benefit is increased absorption of iron from food. And, though vitamin C probably won't prevent it, it may lessen a cold's severity and duration.

How much you need:
Recommended daily allowance (RDA) and tolerable upper intake (UI) level in milligrams. (See the chart.)

Note: Smokers need 35 milligrams per day more than nonsmokers.

Where you get it:
The best food sources are citrus fruits (such as grapefruits and oranges) and their juices, berries, kiwifruit, peppers, broccoli, potatoes and melons. Since cigarette smoke decreases vitamin C stores in the body, smokers need more vitamin C than nonsmokers. But nonsmokers who live with smokers also need to boost their vitamin C intake. One study, published in the American Journal of Clinical Nutrition, found a significant reduction in plasma vitamin C levels in children aged two to 12 who were exposed to smoke. Although there is no established vitamin C requirement for kids who are regularly exposed to secondhand smoke, they should be encouraged to eat foods rich in this vitamin.

See food source chart.

Can you take too much?
Consuming more than the recommended daily allowance of vitamin C probably won't hurt you because this vitamin is water-soluble and any excess is likely excreted through the urine. However, while this vitamin acts as an antioxidant when consumed at moderate levels, some scientists believe that high levels may act conversely as a pro-oxidant, causing certain cancers. But more research is needed in this area, and until all the answers are in, you should not consume more than the tolerable upper intake level. Think twice about megadoses — you're likely peeing your money away or worse.