The old theory about vitamin C, that it helps prevent the common cold, still hasn't proved true.
But a new study says it might help prevent something more important: heart disease.
A study tracking more than 85,000 nurses over 16 years found that those taking vitamin C supplements had a 28 percent lower risk of getting heart disease.
"Mama was right - drink your orange juice," joked Dr. Joel Strom, director of the division of cardiovascular disease at the University of South Florida.
The study doesn't conclusively prove that vitamin C helps prevent heart disease, and doctors aren't ready to recommend it to all patients. But Strom and others said the study should reassure those who choose to take it.
"People who want to take vitamin C won't be harmed," Strom said. "That's one of the key findings."
Biochemist Balz Frei, director of the Linus Pauling Institute at Oregon State University, called the study "very intriguing." Frei wrote an editorial to accompany the study, both published in today's issue of the journal Cardiology.
"A multivitamin makes a lot of sense to me as health insurance," Frei said.
The maximum benefit would come from taking 400 to 500 mg per day, Frei said. The body can't absorb more.
Vitamin C, or ascorbic acid, is found in citrus as well as other fruits and vegetables. The U.S. recommended dietary allowance is 90 mg a day for men and 75 mg a day for women.
The study used data from the Nurses' Health Study, run by researchers from Harvard University and several Boston hospitals and funded by the National Institutes of Health.
Starting in 1976, nurses completed questionnaires every two years, answering detailed information about what foods they ate. About 19 percent of them took daily vitamin C supplements.
Sixteen years later, 1,356 women had developed heart disease. But women taking supplements were less likely to do so.
But scientists still are cautious. They pointed out that the nurses chose whether to take vitamin C. Despite the size of the study, the results don't carry as much weight as a clinical trial, in which doctors assign patients at random to take a drug or a dummy pill, then compare the results.
Doctors are even more cautious after last year's findings that hormone therapy, after years of observational studies that showed benefits, actually proved harmful in clinical trials.
"We learned a lot from the hormone lessons," said Kevin Garner, director of cardiac rehabilitation at Bayfront Medical Center in St. Petersburg. "What makes sense and looks appealing . . . could still be wrong."
Just as with hormone therapy, women who took vitamin C were more likely to exercise and less likely to smoke. Researchers took those factors into account and adjusted their findings, but it's still possible that some lifestyle differences couldn't be measured.
Researchers believe vitamin C helps keep low-density lipoprotein, the "bad" cholesterol that contributes to heart disease, from building up on artery walls.
Other vitamins and foods, from beta carotene to soy, are being studied in search of the same effect - keeping bad cholesterol from oxidizing, which makes it more likely to stick to arteries.
"Is there this perfect antioxidant out there that will do the job?" Garner said.
In this study, researchers didn't find a connection between getting vitamin C from fruits and vegetables and a reduced risk of heart disease. That could be because the questionnaires are an imprecise way of measuring what people really eat. But researchers also said it could be a sign that vitamin C itself, not just other substances in foods, has a benefit.
"They do have pretty compelling data that in this particular study, vitamin C did have an effect, it's not just eating fruits and vegetables," Frei said.More may be better
f,10,hr0 rr Vitamin C is found in citrus and other fruits and vegetables. The U.S. recommended dietary allowance is 90 mg a day for men and 75 mg for women. Taking a supplement that raises that to 400 to 500 mg per day would give the maximum benefit, an expert says.