Brigham launches large study to see if chocolate compounds can prevent heart disease

With the recent placement of deep dark chocolate bars in the “health food aisle’’ at CVS pharmacies, Brigham and Women’s Hospital researchers announced Monday that they’ve received a $20 million grant from industry to determine whether chocolate components act like a drug to protect our hearts.

The 18,000 healthy volunteers won’t be eating chocolate bars but will be randomly assigned to take a daily supplement with cocoa flavanols — equivalent to the amount in a medium size dark chocolate bar — or a placebo for at least four years to see whether it will prevent heart attacks, strokes and heart disease deaths.


“The amount of flavanols they’ll be getting is more than 10 times the average chocolate intake by Americans,’’ said Dr. JoAnn Manson, chief of the division of Preventive Medicine at Brigham who will lead the trial. “Eating this amount in chocolate would lead to significant weight gain.’’

She and her colleagues will also be the first to try to determine whether women who take a typical multivitamin — containing the daily recommended amounts of more than 20 vitamins and minerals — develop fewer cancers than those who take placebos.

The only previous large trial to test multivitamins for cancer prevention, also conducted at the Brigham, involved just men.

Don’t think about joining the study, though, unless you’ve already volunteered for other research studies at Brigham. Female participants age 65 and over will be recruited from those who participated in the Women’s Health Initiative — which Manson also led — while men age 60 and older will be recruited from a pool who volunteered for but were unable to join a trial of vitamin D and fish oil supplements, another study led by Manson that is underway.

Nutrition researchers not involved in the new trial reacted enthusiastically to the possibility of learning once and for all whether taking a daily multivitamin can help healthy people avoid cancer and whether cocoa flavanols would live up to the heart-protective promise seen in small clinical trials of short duration.


A 2012 analysis of 42 small clinical trials involving a total of nearly 1,300 patients found that eating cocoa flavanols in chocolate, cocoa, or supplements for a few weeks or months had beneficial effects on blood pressure, insulin, and cholesterol levels with no side effects.

“I’m 90 percent certain they’ll find something beneficial with cocoa flavanols,’’ said Eric Ding, a nutrition researcher at the Harvard School of Public Health. “For multivitamins, it’s really hard to say. I’m in the camp where I do think they have some benefit, but I’m not sure the study will be long enough to really see if cancers can be prevented.’’

The earlier study of multivitamins in men found that those who took multivitamins for nearly 15 years had only a slightly lower risk of getting cancer compared with a placebo group. The benefits were larger for men over 70, who had an 18 percent lower risk of getting cancer, according to Manson, who helped conduct the research published two years ago in the Journal of the American Medical Association.

Based on that finding and a handful of smaller studies, a large government-sponsored task force concluded last month that there was insufficient evidence to recommend for or against taking multivitamins for cancer prevention. “I think it’s terrific and really exciting that this study will be done; it’s exactly the kind of research that we called for,’’ said Dr. Virginia Moyer, chairwoman of the group, which is called the US Preventive Services Task Force.

Results aren’t expected until 2019.

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