High levels of toxic metals detected in popular chocolate brands

A George Washington University study found significant heavy metal contamination in U.S. cocoa products, particularly organic ones, highlighting the need for cautious consumption due to potential health risks.

The authors suggest that those who enjoy dark chocolate should consider limiting their consumption to one ounce per day to be on the safe side.

A recent study from George Washington University found that a worrying percentage of cocoa products in the United States exceed limits for heavy metals, with organic products having even higher concentrations.

GW researchers tested 72 consumer cocoa products, including dark chocolate, every two years over an eight-year period for contamination with lead, cadmium and arsenic, heavy metals that pose a significant health hazard in sufficient quantities.

“We all love chocolate, but it’s important to consume it in moderation, as with other foods that contain heavy metals, including large fish like tuna and unwashed brown rice,” said Leigh Frame, director of integrative medicine and associate professor of clinical research and leadership at the GW School of Medicine and Health Sciences. “While it’s not practical to completely avoid heavy metals in your diet, you should be mindful of what and how much you eat.”

The unique study was led by Leigh Frame and lead study author Jacob Hands, a medical student researcher in the Frame-Corr lab at the GW School of Medicine and Health Sciences.

The researchers used a maximum allowable dose threshold to assess the extent of heavy metal contamination in a range of chocolate products found on grocery store shelves.

Main conclusions:

  • 43% of the products studied exceeded the maximum admissible dose of lead.
  • 35% of the products studied exceeded the maximum authorized dose for cadmium.
  • None of the products exceeded the maximum permitted dose for arsenic.
  • Surprisingly, products labeled organic had higher levels of lead and cadmium than non-organic products.

Key takeaways:

For the average consumer, consumption of a single serving of these cocoa products does not pose significant health risks, given the median concentrations observed. However, consumption of multiple servings or combining consumption with other sources of heavy metals could result in exposures exceeding the maximum permitted dose.

Foods with high lead content may include animal-based foods that can bioaccumulate heavy metals (shellfish, offal) and plant-based foods or supplements grown in contaminated soils and/or imported from countries with less stringent regulations (e.g., China, Nigeria, India, Egypt). For cadmium, the main concerns are the same with the addition of certain seaweeds, particularly Hijiki seaweed. Consumers should be aware of the potential risks of cumulative exposure, particularly with cocoa products labeled organic, as they may contain higher concentrations of heavy metals. A serving of dark chocolate is typically 30 g and has been widely suggested to have health benefits, including cardiovascular health, cognitive performance, and chronic inflammation. However, research is limited and concerns about heavy metals have not yet been addressed.

Reference: “A Multi-Year Heavy Metal Analysis of 72 U.S. Dark Chocolate and Cocoa Products” by Jacob M. Hands, Mark L. Anderson, Tod Cooperman, Jared E. Balsky, and Leigh A. Frame, June 25, 2024, The Frontiers of Nutrition.
DOI: 10.3389/fnut.2024.1366231

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