New Studies Contradictory on Antioxidants and Chronic DiseaseRisk

New Studies Contradictory on Antioxidants and Chronic DiseaseRisk

OXFORD, England--Two recent studies hadcontradictory conclusions on the impact of vitamin supplementation on chronicdisease risk. The first study, released July 6, found that taking antioxidantvitamins does not significantly reduce the risk of mortality from or incidenceof vascular disease, cancer or other major causes of morbidity (Lancet,360, 9326:7-22, 2002) (www.thelancet.com).

Researchers from the Heart Protection Study at the ClinicalTrial Service Unit and Epidemiological Studies Unit of Radcliffe Infirmaryrandomly assigned 20,536 subjects (aged 40 to 80) to either a vitaminregimen--600 mg/d of synthetic alpha-tocopherol, 250 mg/d of vitamin C and 20mg/d of beta-carotene--or placebo for five years. Of the more than 20,000subjects, 8,510 reported previous myocardial infarction, 4,876 a history ofcoronary disease, and 7,150 no history of coronary disease. Of the 7,150participants without a history of coronary disease, 1,820 had cerebrovasculardisease, 2,701 had peripheral arterial disease, and 3,982 had diabetes mellitus(with some having more than one of these three conditions).

With an average of 83-percent adherence to treatment during thefive-year trial, subjects taking vitamins exhibited a two-fold increase inplasma concentrations of alpha-tocopherol, a one-third increase in vitamin Clevels and a four-fold increase in beta-carotene levels. However, the vitaminregimen was not seen to reduce the risk of mortality--1,446 deaths were reportedin the vitamin group versus 1,389 deaths reported in the placebo group.

Additionally, vitamin supplementation was not found to reducethe risk of any of the primary outcomes, which included the effects ofsupplementation on "major coronary events" (defined as non-fatalmyocardial infarction or death from coronary disease) and on fatal coronaryheart disease. Nor did supplementation reduce the risk of any of the secondaryoutcomes, which included: 1) the effects on major coronary events and on"major vascular events" (defined as major coronary events, strokes ofany type and coronary or non-coronary revascularizations) during the first twoyears and during the latter years of scheduled treatment; and 2) on non-fatal orfatal strokes of any type. And, supplementation was not found to reduce the riskof tertiary outcomes, including site-specific cancer, cerebral hemorrhage,vascular procedures and hospitalization for various causes.

"Based on the presumption that the likelihood of benefitoutweighs any low probability of harm, daily supplementation with a few hundredmg of vitamin E (and with other vitamins) has been recommended for middle-agedand older people," the authors wrote in their conclusion. "But,despite assessing the combined effects of several years of substantial dailydoses of different antioxidant vitamins (including 600 mg of vitamin E) in alarge number of high-risk people, the Heart Protection Study has not been ableto demonstrate any benefit from such supplementation."

In contrast to this study, researchers from Beth IsraelDeaconess Medical Center and Harvard Medical School compiled a research review,which was published in the June 19 issue of the Journal of the AmericanMedical Association (287, 23:3116-26, 2002) (www.jama.com),indicating vitamin intake is essential for health. "Inadequate intake ofseveral vitamins has been linked to chronic diseases, including coronary heartdisease, cancer and osteoporosis," the researchers wrote. Their reviewincluded English-language articles about chronic disease and vitamin intake thatwere published from 1966 through Jan. 11, 2002.

In an accompanying editorial, the same authors wrote, "[L]owlevels of the antioxidant vitamins--vitamins A, E and C--may increase risk forseveral chronic diseases. Most people do not consume an optimal amount of allvitamins by diet alone. Pending strong evidence of effectiveness from randomizedtrials, it appears prudent for all adults to take vitamin supplements."

In late June, the Council for Responsible Nutrition (CRN)released a 100-plus page report--The Benefits of Nutritional Supplements(www.crnusa.org/benefits.html)--whichprovides an overview of more than a decade's worth of scientifically relevantstudies supporting the health benefits of multivitamins and antioxidants, aswell as calcium, omega-3 fatty acids and vitamins D, B6, B9 (folic acid) andB12. "These nutrients are the ones that we considered to be the bestdeveloped, based on the science behind them," said Annette Dickinson,Ph.D., vice president of scientific and regulatory affairs at CRN as well as thereport's author.

"The impact of a rational use of dietary supplements canhelp reduce health care costs that escalate every year as our population growsolder," said Jeffrey Blumberg, Ph.D., a professor at the School ofNutrition Science and Policy at Tufts University who reviewed the CRN reportbefore it was published.