On December 15, 2022, Consumer Reports published an article in which they report that some dark chocolate bars contain excessive amounts of cadmium and lead. Cadmium and lead are heavy metals that have been linked to adverse health effects.

Scientists at Consumer Reports measured the amount of heavy metals in 28 dark chocolate bars from a variety of brands. Cadmium and lead were detected in all of the bars that were tested. Further, the article notes that for 23 of the bars, eating an ounce per day could exceed levels established by public health authorities and Consumer Reports.

The article notes that dark chocolate has a reputation for being healthier treat because of its cocoa solids which include antioxidants. However, the cocoa solids also contain the heavy metals. For that reason, the article concludes that dark chocolate is generally higher in heavy metals than milk chocolate.

Research shows that lead and cadmium may get into the cacao in different ways – with cadmium being absorbed from the soil during growth and lead getting in after beans are harvested. Thus, Consumer Reports suggests that addressing the contamination will require different solutions for each heavy metal. In the meantime, the article urges consumers to be mindful of the risks and minimize potential harms where possible.