Heart Health

Heavy metals found in popular brands of dark chocolate

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By , Executive Editor, Harvard Heart Letter

photo of dark chocolate squares

Because dark chocolate is a rich source of beneficial plant compounds called flavanols, it’s often touted as a heart-healthy treat. However, many popular brands of dark chocolate contain potentially worrisome levels of lead and cadmium, according to a study by Consumer Reports published in December 2022.

Consistent, long-term exposure to even low levels of either of these heavy metals has been linked to various health problems, including cardiovascular disease. Researchers used California’s maximum allowable dose levels for lead (0.5 micrograms, or mcg) and cadmium (4.1 mcg) to gauge the risk posed by dark chocolate. For 23 of the 28 chocolate bars they tested, eating just an ounce per day would put an adult over the maximum dose for at least one of the heavy metals. Five bars contained levels over the limit for both lead and cadmium.

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About the Author

photo of Julie Corliss

Julie Corliss, Executive Editor, Harvard Heart Letter

Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine. She … See Full Bio
View all posts by Julie Corliss

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