Oranges, grapefruits and other vitamin C-loaded foods have many health benefits. But study after study has shown that the vitamin does little—if anything—to cure, prevent or even shorten the duration of the common cold.
The most recent roundup of vitamin C research, published this spring in the Cochrane Database of Systematic Reviews, evaluated several decades of studies that included more than 11,000 subjects taking 200 or more milligrams of vitamin C each day. (The government's recommended daily allowance is 60 milligrams.) The research found that vitamin C did little to reduce either the length or severity of colds among the general population. However, studies have found that it may lower the risk of catching a cold among people whose bodies are under high physical stress—think marathon runners or soldiers on subarctic exercises. They were 50 percent less likely to catch a cold if they took a daily dose of vitamin C.
For the rest of us, however, that extra glass of orange juice is not going to do much. "The presumption of the millions of people who are taking vast amounts of vitamin C that they're preventing a cold has no foundation," says Robert Douglas, lead author of the study and former president of the Public Health Association of Australia.
So where did the vitamin C-cold connection start? It all stems from Linus Pauling, a Nobel Prize-winning chemist who lived from 1901 to 1994. In 1970 he wrote the book "Vitamin C and the Common Cold," which popularized the notion that this particular vitamin could prevent one of the most common ailments on earth. But the book came with little scientific backing and was largely devoid of evidence, says Pauling biographer Thomas Hager. "He published this very influential health book without writing a single scientific paper on the subject," he says. "He seemed to be prescribing a major change in dietary habits without much evidence." Nonetheless, the book's message stuck.
While the cold-killing effect may not exist, doctors have little incentive to correct the notion that it does, since consumption of vitamin C is not considered a public threat. (In fact, some studies have associated vitamin C's antioxidant properties with a decreased incidence of some cancers.) "Is it worth trying to dissuade people?" asks Arnold Monto, a professor of epidemiology at the University of Michigan's School of Public Health. "You've got to choose your battles in public health. Having an extra glass of orange juice may do some good, and it certainly isn't going to do a lot of harm."
In short, if you like the taste of orange juice, then drink up. But keep the tissues handy.