Vitamin C
Myth: Taking high doses of vitamin C will prevent a cold.
Reality: The function of vitamin C in the prevention and treatment of the common cold has been a focus of controversy for the past sixty years. Public interest in the topic persists, and vitamin C continues to be widely sold and used as a preventive and curative agent for this common illness. Unfortunately, studies conducted over the past forty years have all come to the same conclusion: There is no conclusive evidence to support the notion that taking large doses of vitamin C will prevent one from getting a cold. So, where did this myth originate from?
In 1970, Nobel Prize-winning scientist Linus Pauling’s book, Vitamin C and the Common Cold, was introduced to the general public. The book’s main assertion was that taking one gram (1,000 mg) of vitamin C daily would reduce the occurrence of colds by 45 percent for the majority of people, while others might need to take much larger amounts. Dr. Pauling’s subsequent books suggested people take even more vitamin C (as much as 2,300 mg or more a day) for optimum health. Consequently, millions of Americans became convinced that taking large doses of vitamin C would keep them from getting sick.
The popular belief that vitamin C can ward off colds was put to test in a study done by Dr. Terence Anderson and his colleagues at the University of Toronto. Anderson divided some 3,500 volunteers into eight groups: six groups were given various daily dosages of vitamin C, while two groups were given placebos for three months. At the end of the experiment, researchers found that there was no difference in the incidence of colds found among the group taking the placebos and those taking vitamin C dosages of 250 mg, 1,000 mg, or 2,000 mg daily. In fact, volunteers who took dosages of 4,000 mg or 8,000 mg per day when a cold began did no better than those taking only 250 mg per day. However, researchers noted that the severity of cold symptoms decreased slightly in the vitamin C group. For those who took vitamin C (250 mg or higher per day) before they became sick, the illness did not last as long.
The Upside: Since our bodies do not produce vitamin C, it is important that we get it from other sources like fruits, vegetables, and/or supplements. Vitamin C has natural antihistamine properties and assists in neutralizing pollutants. It aids in your body’s ability to fight off “foreign” invaders and is needed for antibody production. Vitamin C is also vital to the production of collagen, which is involved in the building and health of cartilage, joints, skin, and blood vessels.
The Downside: In healthy adults, the most common adverse reaction to a high dose of vitamin C is gastrointestinal and includes nausea, abdominal cramps, flatulent distention, and chronic diarrhea. These reactions are attributed to the slow change in concentration of unabsorbed vitamin C passing through the intestine. Rare adverse reactions have been reported in healthy individuals taking high oral doses of vitamin C. These include elevation of serum glucose, gastrointestinal obstruction, and esophagitis (inflammation of the esophagus). High doses of vitamin C also increase the risk of kidney stones.
In conclusion, high dosages of Vitamin C won’t stop you from getting sick, but it might help you, to some extent, recover faster from the colds you do catch. As the experiment mentioned above implies, when high doses of vitamin C are administered after the onset of cold symptoms, there is no consistent effect on either the duration or severity of symptoms. However, regular vitamin C supplementation (at least 250 mg per day prior to illness) has been associated with a small reduction in the duration and severity of common cold symptoms. Although more studies are needed to look at the effects of large vitamin C doses, one thing is for certain: The belief that taking large dosages of vitamin C to prevent a cold is nothing but a myth.