March 1, 2001 (San Antonio) -- If you're counting on vitamins to help prevent heart disease, you may want to start taking them early. Research presented here at the American Heart Association epidemiology meeting suggest that vitamin E supplements and vitamin C-rich foods only help if you take them before you show signs of heart disease.
The theory behind taking antioxidant vitamins -- vitamin E and vitamin C -- is that they can block the artery-blocking effects of cholesterol. But studies investigating the role of these supplements have been wildly contradictory.
Last year, University of Southern California researcher James H. Dwyer, PhD, reported preliminary data showing that vitamin C supplements actually increase the risk of heart disease. Now intermediate data support that finding -- but suggest that a diet rich in foods that contain vitamin C helps prevent heart disease. The study also finds that high-dose -- but not low-dose -- vitamin E supplements are protective.
"We found that only people with high intake of vitamin E supplements -- 500 to 1,000 IU/day -- showed markedly reduced arterial-wall thickness," Dwyer says. "This was a bit surprising as vitamin E has previously shown protection at lower doses."
The most alarming finding in early trial data was that vitamin C supplements appeared to do far more harm than good.
"We still find an adverse relationship between high-dose vitamin C supplements and disease progression," Dwyer tells WebMD. Substances thought of as antioxidant, such as vitamin C, could work in the opposite way in high doses -- causing damage to tissue and possibly heart disease, Dwyer says.
Getting vitamin C from foods instead of a pill bottle made a gigantic difference.
"If you look at vitamin C levels in the blood, higher levels look more protective -- but that is driven by the effects of dietary vitamin C intake," Dwyer says. "One explanation is that vitamin C intake from food is a marker of fresh fruit and vegetable intake. So if you are getting vitamin C along with fiber and the other benefits of healthy food, I would expect to see a benefit."
Other studies presented at the conference suggest that the reason why vitamin E studies have been so difficult to interpret is that they often enroll patients who already have heart disease.
"Our hypothesis is that for populations with severe heart disease, it is too late to take vitamin E," says researcher Eric Rimm, ScD, of the Harvard School of Public Health.
Rimm led a study of vitamin E supplements (100 IU/day) in 38,884 men aged 40-75 without heart disease. Those who received vitamin E had a 25% reduction in risk of heart disease.
"We found that vitamin E lowered risk, but that it is much more effective in those without pre-existing disease," Rimm says. "We should not be throwing vitamin E aside. I think eventually we will prove that vitamin E is important in the primary prevention of heart disease."
Ronald M. Krauss, MD, senior scientist and head of the molecular medicine department at Lawrence Berkeley National Laboratory in Berkeley, Calif., is the official AHA spokesman for nutrition.
"The AHA has found no conclusive evidence that vitamin E supplementation prevents heart disease," says Krauss, who would not say whether he himself takes the vitamin. "These observational studies are not controlled, and without a series of clinical trials showing a benefit, we urge great caution in interpreting this data."