Can Vitamin C Shorten a Cold?

Vitamin C, Zinc, Echinacea May Help

From the WebMD Archives

Oct. 2, 2002 -- There is still no cure for the common cold, but as the season of sniffles and sneezes approaches are there any proven remedies to lessen the misery they bring? Do megadoses of vitamin C really help? How about echinacea and zinc?

Americans spend billions on the supplements each year, and while some studies have shown them to be effective for reducing the length or severity of colds, the evidence remains inconclusive.

It has been three decades since Nobel-prize winning chemist Linus Pauling told the world that megadoses of vitamin C prevented colds and lessened their severity. The latest study to weigh in on the issue found that people who took a patented form of vitamin C, known as Ester C, during cold season had fewer colds and less severe symptoms than those who took placebos.

There were 37 colds among the 84 study participants who took vitamin C, compared to 50 colds among an equal number of participants who took a placebo. The study was published last spring in the journal Advances in Therapy.

The findings contradict most studies conducted since Pauling published the book, Vitamin C and the Common Cold in 1997, Stephen Lawson of The Linus Pauling Institute tells WebMD. These studies did not find, as Pauling originally claimed, that vitamin C prevents colds from occurring.

"There is good evidence that large doses of vitamin C shorten the duration of the common cold by about a day and that symptoms are ameliorated," he says. "Some people say a one-day reduction is not meaningful, but if you think of it in terms of the entire population of the United States, you are talking about a substantial impact in terms of public health and economic consequences."

People with colds need to take 1,000 or 2,000 mg (1 or 2 grams) of vitamin C a day to gain a therapeutic effect, Lawson says.

Karla Birkholz, MD, tells WebMD there is little conclusive evidence regarding the effectiveness of vitamin C, the herbal supplement Echinacea, or zinc lozenges.

"We just don't know a lot," she says. "The early studies suggested that Echinacea had an antiviral effect, but newer, better-designed studies don't back that up. There is a little better evidence that zinc is effective for shortening the course of a cold, but again, it is inconclusive."

Like the vitamin C studies, those finding that Echinacea and zinc shorten the length of colds suggest a modest reduction of a day or so. And while all three supplements are touted as reducing cold symptoms, Birkholz says this is very difficult to prove in clinical studies.

"You can't really measure how sick you would have been without the treatment," she says. "But the bottom line is that these supplements appear to be safe, and they may do some good. We just don't know."

The Phoenix doctor says the best way to prevent a cold is to take good care of yourself during cold season. In other words, eat well, exercise, get enough sleep, don't smoke, and keep stress to a minimum.

She also recommends washing hands frequently, and sneezing into your arm, instead of your hand, to avoid spreading germs each time you touch something.

"It sounds kind of silly," she says. "But if you think about it, it makes perfect sense."