Myth: Vitamin C prevents the common cold.

Fact: After decades and dozens of studies, it appears the idea that vitamin C prevents colds is just an old wives’ tale. But there is some evidence that high doses of the vitamin, which is found in citrus fruit and other produce, may slightly shorten the length of a cold.

The conclusions come from a 2004 study by researchers at Australia’s National Centre for Epidemiology and Population Health who reviewed more than 30 published trials investigating vitamin C’s ability to prevent and treat the cold.

Combined, the studies involved more than 10,000 participants. The reviewers determined that people taking vitamin C daily, in doses as high as 1 gram, caught roughly the same number of colds as people who were not taking extra vitamin C.

The combined trials also found that cold symptoms did not last quite as long in people who took extra vitamin C daily through several winter months. On average, colds for these people were about half a day shorter than for people who did not take vitamin C.

In addition to taking on colds, the body uses vitamin C, also known as ascorbic acid, to strengthen bones, cartilage and muscle, and aid in the absorption of iron. The National Institutes of Health recommend 90 milligrams of vitamin C per day for men and 75 milligrams for women.

If you’re looking to boost your vitamin C intake with vitamin pills or powder, research at Purdue suggests you shouldn’t store the vitamin in the bathroom or kitchen. Vitamin C is a crystalline substance that will dissolve in water. Steamy places, like near showers or cooking surfaces, will deplete the vitamin’s strength in as little as one week, even if it’s stored in a container with a lid.

Citrus fruits, dark green vegetables, peppers, strawberries and cantaloupe are all good natural sources of vitamin C, but storage and cooking can take their toll. The longer a food is stored, the more vitamin C it loses, and cooking and steaming dissolves some of the nutrient. To maximize the vitamin C you get from food, the National Institutes of Health recommend eating fruits and vegetables fresh and raw.

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Kathryn Roethel