Many cocoa products, especially dark chocolate, contain heavy metals including lead and cadmium that exceed recommended safety guidelines, according to a new study. Somewhat surprisingly, higher concentrations of these toxins were found in organic products.[1]
“Consumers should be aware that certain products may expose them to undesirable levels of certain heavy metals,” says the lead author, Jacob Hands, a medical student at the GW School of Medicine and Health Sciences in Washington, DC.
Cadmium and lead are inherently toxic, and if they accumulate in the body, they can affect nearly every single major organ in the body, he says.
“Therefore, the consumption of certain cocoa products over time, and among certain groups, such as pregnant women and children, could be problematic,” says Hands.
Researchers Tested the Most Popular Dark Chocolate and Cocoa Products
While many studies have found heavy metal contamination in chocolate products, the precise amount of the contaminants has been mostly unexplored, according to the authors.
For the study, researchers analyzed 72 of the most popular chocolate items according to an annual consumer survey. The items were purchased on the internet or in grocery stores every other year over an eight-year period.
Scientists tested each product for contamination with three heavy metals — lead, cadmium, and arsenic — to find out if they exceeded allowable dose levels. The study design assumed a person ate one serving per day, and measured that against maximum allowable levels set by California’s Proposition 65.
The study found that 43 percent of the products studied exceeded the maximum allowable dose level for lead, while 35 percent of the products exceeded the maximum allowable dose level for cadmium. None of the products exceeded the maximum allowable dose level for arsenic.
Surprisingly, organic products showed higher levels of both lead and cadmium than non-organic products.
According to the authors, the findings suggest that people should eat dark chocolate and other cocoa products in moderation, as is recommended for other foods that contain heavy metals, including unwashed brown rice and large fish like tuna.
“For the average person, consuming a single serving of these cocoa products may not pose significant health risks based on the median concentrations found. However, consuming multiple servings or combining consumption with other sources of heavy metals could lead to exposures that exceed the maximum allowable dose level,” says Hands.
The fact that a few products had unacceptably high levels of cadmium, and more rarely, lead, should prompt calls for stronger evaluation of cocoa quality and sources, according to the authors.
Chocolate lovers should be aware that in general, cocoa products labeled organic had higher heavy metal concentrations, they wrote.