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Dark Chocolate May Pose Slight Heavy Metal Risk to Children

Bits of chocolate stacked.
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Most dark chocolate bars don’t pose a heavy metal health risk to adults or children, according to a new study.

A minority of bars (4 out of 155) tested by researchers, however, did contain levels of cadmium unsafe for children to consume in excess (more than 2 bars per week).

The findings appear to stand in contrast to the well-publicized results of a 2023 Consumer Report, which concluded that a third of chocolate products tested contained harmful levels of lead and cadmium.

The results of the new study were published in Food Research International.

Heavy handed

Cocoa crops can absorb heavy metals, particularly cadmium, from surrounding soil. The harvested cocoa beans can then become contaminated with lead during handling and processing.

Cadmium exposure has been linked with a heightened risk of cancers and kidney, bone and lung diseases. Lead exposure can lead to anemia, hypertension and renal impairment.

To help determine the level of heavy metals in chocolate in the US, Tulane University researchers first went out to stores and bought 155 chocolate bars, 101 of which were dark chocolate, all made from cocoa sourced from 5 major regions: Asia Pacific, West Africa, East Africa, South America and Central America.

Samples from bars were tested for 16 heavy metals, ranging from the toxic (lead and cadmium) to the essential (copper, iron, zinc).

To gauge the safety of eating the bars, the researchers modeled the risk of eating 1 ounce (28 grams) of the chocolates per day, which is equivalent to consuming more than 2 whole chocolate bars a week.

For every respective heavy metal, the average level found in the 155 bars was within acceptable, safe-to-consume limits for adults.

Only 1 brand of Colombian dark chocolate exceeded the international limit for cadmium in bars (800 micrograms per kilogram) set by the European Commission Regulation. Four dark chocolate bars contained cadmium levels that could pose a risk to children weighing 33 pounds (15 kilograms) or less, the average weight of a 3-year-old in the US.

“For adults there is no adverse health risk from eating dark chocolate, and although there is a slight risk for children in 4 of the 155 chocolate bars sampled,” said lead author Dr. Tewodros Godebo, assistant professor of environmental health sciences at Tulane University School of Public Health and Tropical Medicine.

Godebo tempered the concerning finding, however, saying that a child would need to consume at least two bars of dark chocolate a week to be at significant risk.

“It is not common to see a three-year-old regularly consume more than two bars of chocolate per week,” she added. “What we’ve found is that it’s quite safe to consume dark chocolate and milk chocolates.”

Cacao originating from West African countries tended to contain lower cadmium and lead levels than those sourced from Central and South America.

Two chocolate bars contained lead levels above California’s interim standards for dark chocolates, but neither bar was determined by the researchers to pose adverse risks to children or adults.

All essential heavy metals (magnesium, calcium, etc.) were more present in the dark chocolate bars than the milk chocolate ones. Several of the bars provided more than 50% of the daily requirement for children and adults – a health benefit of dark chocolates that shouldn’t be overshadowed by the study’s few unsavory findings, said Godebo.

“Not only is it [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.

This article is a rework of a press release issued by Tulane University. Material has been edited for length and content.

Godebo TR, Stoner H, Kodsup P, et al. Occurrence of heavy metals coupled with elevated levels of essential elements in chocolates: Health risk assessment. Food Res Int 2024. doi: 10.1016/j.foodres.2024.114360