A recent study has revealed that dark chocolate and similar cocoa products contain significant levels of lead and cadmium, two neurotoxic metals associated with severe health risks, including cancer, chronic diseases, and reproductive and developmental problems, especially in children. These findings were published in the journal Frontiers in Nutrition.

Lead and cadmium are naturally occurring elements found in the Earth’s crust, making them almost impossible to avoid entirely in agricultural products. The concentration of these metals in crops varies depending on soil composition, and can be exacerbated by the extensive use of metal-containing fertilizers and persistent industrial pollution.

But the study also found that organic dark chocolate, despite being cultivated in environments with fewer pesticides and contaminants, often had some of the highest levels of these toxic metals.

The study focused exclusively on pure dark chocolate products due to their high content of cacao, or the unprocessed part of the cacao bean, and excluded candies or baking chocolates with additional ingredients.

However, it did not disclose the specific brands or manufacturers of the tested chocolate products, leaving consumers with the challenging task of navigating these findings without detailed guidance.

Jane Houlihan, national director of science and health for Healthy Babies Bright Futures, said that the average levels of lead and cadmium found in cocoa-containing products in this study were at or above the average amounts detected by the U.S. Food and Drug Administration (FDA) in some of the most contaminated foods they test, CNN reported.

The study analyzed 72 consumer cocoa products for levels of lead, cadmium, and arsenic over an eight-year period (2014, 2016, 2018, and 2020). Conducted by Consumer Labs, a nonprofit providing third-party testing on health and nutrition products, the research found that 43% of chocolate products exceeded the maximum allowable dose level for lead set by California’s Proposition 65, while 35% surpassed the Prop 65 limit for cadmium. Fortunately, no significant levels of arsenic were detected.

Proposition 65’s limits are stricter than federal standards. The FDA’s maximum allowable level of lead in children’s candy is 0.1 parts per million, whereas Prop 65 sets a safety standard at 0.05 parts per million for chocolate.

In a statement to Fast Company, Christopher Gindlesperger, senior vice president of public affairs and communications for the National Confectioners Association, said, “Chocolate and cocoa are safe to eat and can be enjoyed as treats as they have been for centuries. Food safety and product quality remain our highest priorities and we remain dedicated to being transparent and socially responsible.”

For healthy adults, indulging in one ounce of dark chocolate occasionally poses minimal risk, Tewodros Godebo, an assistant professor of environmental geochemistry at Tulane University, told CNN. “Of course, we want close to zero exposure, but that’s impossible,” he said. “Everything we eat likely contains some level of these contaminants. But it is a relative risk.”

However, the risk of heavy metal exposure from chocolate increases for medically compromised individuals, pregnant women, and young children, he added.

Children are particularly vulnerable, as they can absorb up to 100% of ingested lead on an empty stomach, leading to severe developmental issues, according to the World Health Organization. And over time, consuming low levels of cadmium can damage the kidneys. The Environmental Protection Agency labels cadmium a probable human carcinogen.