Do You Need to Worry About Heavy Metals in Dark Chocolate?

Do You Need to Worry About Heavy Metals in Dark Chocolate?

There’s some good news for dark chocolate lovers: The sweet treat doesn’t pose a health risk for adults, a recent study found. 

For the study, published June 6 in Food Research International, scientists from Tulane University tested more than a hundred dark and milk chocolate bars sold in the U.S. for levels of heavy metals, including toxic ones like lead and cadmium. They concluded that the products are safe for adults and that a small minority may pose a slight risk to young children—but only if eaten in large amounts. 

The findings come a year after a paper by Consumer Reports showed harmful levels of lead and cadmium in some brands of dark chocolate, raising concerns about the safety of eating dark chocolate. 

“What we’ve found is that it’s quite safe to consume dark and milk chocolates,” lead author Tewodros Godebo, PhD, assistant professor of environmental health sciences at Tulane University School of Public Health and Tropical Medicine, said in a press release.

Here’s what you need to know about the study’s findings, what previous research has shown, and what experts uninvolved with the study think about how safe it is to chow down on dark chocolate.

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For the Consumer Reports study, researchers tested 48 products across five categories: cocoa powder, chocolate chips, milk chocolate bars, dark chocolate bars, and mixes for brownies, chocolate cake, and hot chocolate. They focused on lead and cadmium, metals that can impact the brain and nervous system, with children especially vulnerable to symptoms.

The researchers discovered that dark chocolates had higher levels of heavy metals than their milk chocolate counterparts. Every dark chocolate bar tested had detectable amounts of lead and cadmium, with 71% of them exceeding California’s standard maximum allowable dose levels for lead, cadmium, or both.

Researchers used California’s standard because there are no federal limits for how much lead and cadmium most foods can have. The daily maximum allowable dose for lead is 0.5 micrograms (mcg) and 4.1 mcg for cadmium.

The research built on a Consumer Reports study from 2022, which found that 82% of dark chocolate bars tested had levels of lead or cadmium that exceeded California’s threshold.

Cadmium can end up in dark chocolate because cocoa beans absorb it from contaminated soil, James E. Rogers, PhD, director and acting head of product safety testing at Consumer Reports, previously told Health. Lead can get onto the cocoa beans after harvest, potentially from dust and soil, while beans dry outside.

The Tulane team analyzed samples from 155 dark and milk chocolates from a range of brands sold in the U.S., including well-known ones such as Dove, Ghirardelli, Hershey, Lindt, and Trader Joe’s. Each was tested for the presence of 16 heavy metals, ranging from the essential, like copper, iron, and zinc, to the harmful, like lead and cadmium.

Researchers then calculated the risk of eating an ounce of chocolates a day, which equates to more than two chocolate bars a week.

They discovered that only one brand of dark chocolate—Lok Dark Chocolate from Columbia—exceeded the European Union limit of 800 mcg per kilogram (mcg/kg) for cadmium in bars with more than 50% cacao.

Four dark chocolate bars had cadmium levels that the researchers deemed risky for kids who weigh a maximum of 33 pounds, the weight of an average three-year-old in the United States. The bars were:

  • Lok Dark Chocolate
  • Marou
  • Mexican Vivio Foods organic cacao powder
  • Peruvian Pascha dark chocolate chips

Two chocolate bars, Napolitains Dark and Blanxart chocolate, had lead levels above California’s standard of 150 (mcg/kg) for dark chocolates. However, researchers found that they still weren’t likely to harm adults or kids.

“For adults, there is no adverse health risk from eating dark chocolate,” Godebo said. “Although there is a slight risk for children in four of the 155 chocolate bars sampled, it is not common to see a 3-year-old regularly consume more than two bars of chocolate per week.”

The study also found that dark chocolate contained high levels of important nutrients like copper, iron, manganese, magnesium, and zinc. Some bars even had more than 50% of the daily nutritional requirements for kids and adults.

“Not only is [dark chocolate] packed with these essential minerals, but they can potentially reduce the absorption of toxic metals in the intestine since these metals compete for the same site,” Godebo said. “While two previous studies in the U.S. examined the presence of lead and cadmium in chocolate, this study employed the largest sample size, expanded the scope of testing to 16 metals, and included a risk assessment of toxic metals that accounted for the nutritional contribution of essential minerals.”

Portion size is a factor to consider when assessing the risk of eating dark chocolate, Jamie Alan, PharmD, PhD, an associate professor of pharmacology and toxicology at Michigan State University, told Health. “If people are consistently eating more than one ounce of dark chocolate a day,” she explained, the findings from the most recent study “may not be applicable.” 

However, it’s unlikely that most adults “consume enough dark chocolate for these potentially harmful substances to cause a problem,” Deborah Cohen, DCN, an associate professor in the clinical and preventive nutrition sciences department at Rutgers University School of Health Professions, told Health.

She added that dark chocolate does have perks, including being rich in plant chemicals called flavanols that may help protect the heart. 

“Dark chocolate contains up to two to three times more flavanol-rich cocoa solids than milk chocolate,” she said. “Flavanols in chocolate can increase insulin sensitivity in short-term studies; In the long run, this could reduce the risk of diabetes.” 

But Cohen stressed that you shouldn’t start viewing dark chocolate as being on par with fruits and vegetables. “Vegetables contain so many other important nutrients—antioxidants, phytochemicals, fiber,” she said. “However, if one has a craving for a bit of chocolate every once in a while, a bite or two or an ounce or two won’t hurt.”

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