Millions of Americans take multivitamins daily with the goal of improving their health. Some take them in the belief that they can reduce the risk of a heart attack and/or prevent memory decline. Two new studies published on July 17 in the Annals of Internal Medicine evaluated the role of multivitamins for heart attack risk reduction and memory decline prevention.
The study assessing whether multivitamins reduce cardiovascular events and are safe was conducted by researchers at Mount Sinai Medical Center (Miami Beach, Florida), the National Heart, Lung, and Blood Institute and National Center for Complementary and Alternative Medicine (Bethesda, Maryland), Palmer Center for Chiropractic Research (Davenport, Iowa), Duke Clinical Research Institute (Durham, North Carolina), Biogenesis Medical Center (Landrum, South Carolina), Brigham and Women's Hospital and Harvard Medical School (Boston, Massachusetts), and University of Kansas Medical Center (Kansas City, Kansas).
The researchers conducted a double-blind, placebo-controlled, multicenter, randomized clinical trial, meaning that neither the subjects nor the researchers knew which were receiving the multivitamins. The study encompassed 134 US and Canadian academic and clinical institutions. The study group comprised 1,708 patients aged 50 years or older who had suffered a heart attack (myocardial infarction; MI) at least six weeks earlier. The average age was 65 years, and 18% of the subjects were women They were randomly assigned to ingest a 28-component, high-dose multivitamin and multimineral mixture or a placebo.
The researchers assessed the time to total death, recurrent MI, stroke, coronary revascularization, or hospitalization for angina. They found that the MI that qualified the subject for study inclusion occurred an average of 4.6 years before enrollment. The average follow-up was 55 months. The subjects received vitamins/placebo for an average of 31 months in the vitamin group and 35 months in the placebo group. A total of 645 (76%) of the subjects in the vitamin group and 646 (76%) subjects in the placebo group completed at least one year of oral medication; 400 (47%) subjects in the vitamin group and 426 (50%) subjects in the placebo group completed at least three years. A total of 394 (46%) of the subjects in the vitamin group and 390 (46%) subjects in the placebo group discontinued the vitamin regimen; 17% of the subjects withdrew from the study. Death occurred in 230 (27%) of the subjects in the vitamin group and 253 (30%) of the subjects the placebo group. No evidence was found that suggested harm from vitamin therapy in any category of adverse events.
The investigators noted that a limitation of the study was that there was considerable nonadherence and withdrawal; thus, limiting the ability to draw firm conclusions (particularly regarding safety). They concluded that high-dose oral multivitamins and multiminerals did not statistically significantly reduce cardiovascular events in patients after an MI who received standard medications. However, this conclusion is mitigated by the nonadherence rate.
The study evaluating cognitive decline was conducted by researchers at Brigham and Women's Hospital, Harvard Medical School, Harvard School of Public Health, and Veterans Affairs Boston Healthcare System (all located in Boston, Massachusetts). The investigators noted that, despite widespread use of multivitamin supplements, their effect on cognitive function, which is a critical aging issue, remains inconclusive. They explained that to date, no long-term clinical trials have evaluated multivitamin use and cognitive decline in seniors. Therefore, they conducted a study to assess whether long-term multivitamin supplementation affects cognitive function in later life.
The study group comprised 5,947 male physicians aged 65 years or older whowere enrolled in the Physician’s Health Study II; it ran from 1997 through June 1, 2011. As was the MI study, it was a randomized, double-blind, placebo-controlled trial. The cognitive function substudy began in 1998. All subjects received up to four repeated cognitive assessments by telephone interview that were completed over a course of 12 years. The subjects received either a daily multivitamin or a placebo.
The investigators developed a global composite score that averaged five tests of global cognition, verbal memory, and category fluency. A secondary measure was a verbal memory score that combined four tests of verbal memory; this score is a strong predictor of Alzheimer’s disease.
The researchers found no difference was found in average cognitive decline over time between the multivitamin and placebo groups or in the average level of cognition at any of the four assessments. Furthermore, cognitive performance did not differ between the multivitamin and placebo groups on the secondary measure of verbal memory.
The study authors noted that a limitation of the study was that the doses of vitamins may have been too low or the population may be too well-nourished to benefit from a multivitamin. They concluded that in male physicians aged 65 years or older, long-term use of a daily multivitamin did not provide cognitive benefits.