Heart Health
Heavy metals found in popular brands of dark chocolate
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- Reviewed by Christopher P. Cannon, MD, Editor in Chief, Harvard Heart Letter; Editorial Advisory Board Member, Harvard Health Publishing
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.
Chocolate, which is made from seeds of the cacao tree, can be contaminated with cadmium and lead by polluted soil — not only as the crop grows but also during harvesting and processing. You can limit your exposure by choosing dark chocolate brands that Consumer Reports deemed as safer options (see /darkchoc) or simply enjoy it occasionally rather than frequently.
Image: © Rares Caragiale | 500px/Getty Images
About the Author
Julie Corliss, Executive Editor, Harvard Heart Letter
About the Reviewer
Christopher P. Cannon, MD, Editor in Chief, Harvard Heart Letter; Editorial Advisory Board Member, Harvard Health Publishing
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