This article is from the WebMD Medical News Archive

March 12, 2003 (Denver) -- The popular belief that vitamin C can ward off the common cold may have some validity to it, say researchers who have studied changes in immune cells' response to vitamin C.

According to Susan Ritter, a graduate student at the University of Texas Health Sciences Center , several studies have looked at people taking vitamin C and the number of colds that they develop, but no research has looked at the immune system cells' response to vitamin C.

Presenting at the 60th Anniversary Meeting of the American Academy of Allergy, Asthma, and Immunology (AAAAI) on Tuesday, Ritter and colleagues reported that 12 healthy subjects who took one gram of vitamin C a day for two weeks showed a boosted immune system response during that time.

What's more, when they looked at responses in four of the patients, they found that in two of them, the response to vitamin C took place within five hours. According to Ritter, this might mean that taking a vitamin C tablet at the first sign of a cold could achieve an effect quickly enough to ward off that cold. "You may not have to take it every day," she says.

Ritter and colleagues drew blood from the subjects before and after they had taken one gram of vitamin C a day for two weeks. They isolated the immune system cells from the blood of the subjects and measured the levels of immunity boosting substances called cytokines.

Certain virus-fighting cytokines were increased after two weeks of taking the vitamin; however, when they measured the levels two weeks later, they found that the levels had returned to normal, suggesting that the effect is short-lived.

Ritter pointed out that previous studies of vitamin C have recommended several grams a day of vitamin C, which could potentially be toxic. But in their study, the patients took a much lower amount.

"We did not see any toxic side effects in the subjects," she tells WebMD.

Stephen Tilles, MD, with the Northwest Asthma & Allergy Center in Seattle, called the study "impressive" because it measures what's going on at the level of the cell.

"This study legitimizes some of the popular assumptions about vitamin C and helps validate the effect of vitamin C on the immune system," he tells WebMD.

He says that larger studies are needed to test these findings further. But he said, "this is the equivalent of about five glasses of orange juice a day, so it's way more practical and safer than the many grams per day that had been proposed earlier."

SOURCES: 60th anniversary Meeting of the American Academy of Allergy, Asthma, and Immunology, Denver, March 7-12, 2003. Susan Ritter, University of Texas Health Sciences Center, Houston. Stephen Tilles, MD, Northwest Asthma & Allergy Center, Seattle.

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