Vitamin C does little to prevent colds

DEAR DOCTOR K: Whatever happened to the idea that vitamin C can boost your immune system and prevent colds?

DEAR READER: Vitamin C, also known as ascorbic acid, was promoted as a health supplement for decades. It is perhaps best known for its one-time reputation for preventing and treating the common cold. This idea was heavily promoted in the 1970s by one of the 20th century’s most celebrated biochemists, Nobel laureate Linus Pauling. But Pauling did not win the Nobel Prize for his theories about vitamin C.

Vitamin C is crucial for making collagen, the substance that lends structural support to tendons, ligaments, bones and blood vessels.

Vitamin C is also a potent antioxidant. As the cells in our body do their jobs, they produce a group of harmful chemical waste products called “free radicals.” These free radicals are also created by environmental factors such as tobacco smoke, ultraviolet rays and air pollution. Antioxidants can chemically combine with free radicals, rendering them harmless.

Unfortunately, despite the hype, vitamin C does not appear to prevent colds, and its ability to shorten the duration of colds is minimal. A recent summary of 29 studies involving more than 10,000 people confirmed the lack of benefit of regular vitamin C supplementation.

There also is little evidence that vitamin C supplements prevent cancer, heart disease or cataracts.

The recommended daily allowance for men is 90 milligrams per day. Women should get 75 milligrams per day. If you are a smoker, add 35 milligrams per day to your recommended amount. Taking vitamin C supplements in amounts far higher than the RDA offers no proven health benefits, but it probably won’t hurt.

Most people meet the RDA for vitamin C through their diets. Citrus fruits are rich in vitamin C. Sweet red pepper is another excellent, but less well known, source of vitamin C. I’ve put a table listing good food sources of vitamin C on my website, AskDoctorK.com.