Beta-Carotene Supplements May Increase Mortality Risk
by Karla Gale
NEW YORK (Reuters Health) Jun 12 - Beta-carotene supplementation leads to a small but significant increase in all-cause mortality and mortality from cardiovascular disease (CVD), according to results of a new meta-analysis reported in the June 14th issue of The Lancet. And while vitamin E supplementation is associated with no such risk, it does not exhibit clinically beneficial effects. Dr. Marc S. Penn and associates at the Cleveland Clinic Foundation in Ohio analyzed seven randomized controlled trials of vitamin E treatment and eight trials of beta-carotene treatment, all of which included at least 1000 patients.
Beta-carotene use was examined in close to 140,000 patients, among whom all-cause mortality rate was 7.4% in the active treatment group and 7.0% in the control group (p = 0.003). In the six trials that evaluated cardiovascular death specifically, rates of death were 3.4% in the treatment group and 3.1% in the control group. Only one trial failed to show a detrimental effect of beta-carotene on death rates. Dr. Penn's group points out that beta-carotene has adverse effects on lipids, and that cigarette smoking destabilizes the beta-carotene molecule with deleterious results.
Therefore, "the use of vitamin supplements containing beta-carotene and vitamin A... should be actively discouraged," they conclude, and "clinical studies of beta-carotene should be discontinued." Among the more than 80,000 patients included in vitamin E trials, the lack of efficacy leads the authors to "not support the continued use of vitamin E treatment."
In fact, Dr. Penn told Reuters Health that a previous study has shown that vitamin E can block the effects of statins and niacin, which are established therapies. "So I think there's no evidence they're good and there is a hint that they may be harmful." Therefore, Dr. Penn and his associates recommend that vitamin E be excluded in trials of patients at high risk of coronary artery disease. Dr. Penn also noted that ophthalmologists recommend large doses of vitamin supplements for macular degeneration. Certainly, if there is a risk of other diseases, and beta-carotene has been shown to be efficacious, the supplements should still be taken, he added.
Otherwise, "we should really be focusing on healthy diets," he said. "The concept of vitamin supplements to overcome bad dietary habits is not a valid thesis, at least with vitamin E and beta carotene."
However, the Council for Responsible Nutrition, a trade association representing the dietary supplement industry, blasted the Cleveland Clinic's analysis, calling it "irresponsible, over interpreted, and old news disguised as something new for publicity purposes," in a press statement.
The Council further notes that beta-carotene risk is associated primarily with smoking. They also maintain that vitamin E has potential benefits for vision, Alzheimer's disease, cancer and coronary disease.
References: Lancet 2003;361:2017-2023.