Dark chocolate and other cocoa products contain lead and other heavy metals, study finds

A concerning percentage of chocolate products on U.S. grocery store shelves contain levels of heavy metals that exceed guidelines, with the highest concentrations found in organic products, a new study finds.

A multiyear analysis of 72 consumer cocoa products found 43% contaminated with lead above acceptable levels, while 35% surpassed cadmium thresholds, according to research led by scientists at George Washington University and published Wednesday in Frontiers in Nutrition. 

"Cocoa-containing products are notoriously rich in metals owing to cultivation and manufacturing practices required to produce such products," according to the study. "Dark chocolate in particular is a rich source of earth metals and contamination in the course of its processing has been well documented."  

The study based its findings on a California law that sets maximum allowable dose levels for heavy metals in food.

The state regulations are frequently used as a safety standard as the U.S. Food and Drug Administration does not specify limits on heavy metals in most foods, although the agency does have suggested limits for chocolate and sugar-based candy but solely for kids. There is no known safe level of exposure to lead, according to the FDA. 

Surprisingly, organic products were found to contain higher levels of lead and cadmium compared to nonorganic items. 

None of the products surpassed the maximum for arsenic. 

The findings suggest eating less chocolate as a means of limiting exposure, Leigh Frame, director of integrative medicine at George Washington University School of Medicine and Health Sciences.

"Chocolate is not dangerous, it's not that bad. But, as with any food potentially contaminated with heavy metals, diversifying your diet is important so you don't get exposed to the same things, whether it's too much heavy metals in chocolate or too much vitamin A if you're eating carrots," Frame told CBS MoneyWatch. 

The researcher recommends restricting consumption to one ounce of dark chocolate a day — or one third of the average candy bar. "Many people, including myself, have a hard time limiting themselves to an ounce," said Frame. "So have two ounces every other day," the researcher advised. 

"Chocolate and cocoa are safe to eat and can be enjoyed as treats as they have been for centuries," the National Confectioners Association stated in response to the findings.