Test Your Knowledge

Vitamin C is a water-soluble nutrient that people need for normal growth and development. This vitamin helps repair tissues and forms collagen, a protein used to make blood vessels, ligaments, scar tissue, skin and tendons. Vitamin C helps repair wounds and is vital to maintaining healthy bones, cartilage, gums and teeth. Vitamin C also helps the body to absorb iron.

In recent years, there has been a lot of speculation about the role of vitamin C in common cold prevention. Many studies have been conducted, with mixed results. Some studies appear to show that taking anywhere from 1,000 to 6,000 milligrams (mg) of vitamin C daily can reduce the length of a cold by a day, and may slightly relieve symptoms such as runny nose and sore throat.

However, this amount is more than 100 times the recommended dietary allowance (RDA) established by the Food and Nutrition Board of the National Academy of Sciences. This has the potential to lead to health problems. Taking supplemental doses of vitamin C as low as 500 mg daily has been shown to cause diarrhea in some people. Small children and the elderly are particularly at risk for health problems associated with such diarrhea. In addition, other studies have shown that excessive vitamin C consumption has no influence on the number or severity of colds.

Other studies have found that vitamin C supplementation can significantly reduce the number of colds a person catches. Still, experts generally agree that conclusive evidence has yet to emerge about the potential role of vitamin C in preventing colds or reducing the symptoms of these illnesses. The results of some studies even suggest that there may be no link between taking vitamin C and reduced cold symptoms.

For now, people are urged to take only the recommended daily dose of vitamin C. The body is capable of absorbing about 200 mg of vitamin C at one time. Any excess of the vitamin is excreted in urine. Although it is unclear whether or not vitamin C protects against colds, drinking vitamin C-rich beverages, such as orange juice and grapefruit juice, does provide fluids and extra energy necessary to return a patient to good health. Fruits and vegetables contain vitamin C and other important nutrients such as fiber.

Vitamin C does play a role in the immune system. Immune system cells appear to take in high amounts of the vitamin. There has been at least anecdotal evidence of vitamin C helping to fight many different forms of infection, not just the common cold. For example, some studies suggest that vitamin C may help to fight the bacteria that cause stomach ulcers.

The Food and Nutrition Board of the National Academy of Sciences has issued the following RDAs for vitamin C. The figures are expressed in milligrams: