Heavy metals in dark chocolate pose 'minimal risk' to kids, none for adults, finds new study
Some good news for dark chocolate lovers: Your favorite bittersweet or semisweet treat is safe to eat and poses a low risk of toxic metal ingestion, a new study suggests. The research, published in the journal Food Research International, counters the alarming findings from Consumer Reports last year that found concerning levels of lead or cadmium in about a third of the chocolate they tested.
Here’s what we know now, and why experts say you can have your dark chocolate and eat it too.
What was the concern over metal in chocolate?
In 2023, Consumer Reports found levels of the toxic heavy metals lead and cadmium above California’s allowable standard in 16 out of 48 chocolate products they tested. They looked at a number of types of chocolate: hot chocolate mixes, brownie and cake mixes, cocoa powders, chocolate chips and dark and milk chocolate bars.
Dark chocolate products were most likely to exceed the levels of cadmium or lead considered safe by California, compared to milk chocolate products. Chocolate bars were the worst offenders: 23 out of 28 dark chocolate bars, including those made by Divine Chocolate and Walmart’s in-house brand, Sam’s Choice, had elevated levels of lead or cadmium.
The findings led Consumer Reports to warn that “kids and pregnant people should consume dark chocolate sparingly, if at all, because heavy metals pose the highest risk to young children and developing babies,” the report authors wrote in 2023.
What are the dangers of toxic heavy metals?
Heavy metals are a group of relatively dense metals that occur in nature. Some, like zinc and magnesium, are harmless or even beneficial nutrients. But others, including lead, cadmium and arsenic can be harmful.
“Heavy metal poisoning can lead to a weakened immune system, impaired behavior and psychology, disabilities and higher prevalence of gastrointestinal cancers,” Bryan Quoc Le, a food scientist and consultant, tells Yahoo Life. Lead, which has recently been found in high amounts in Lunchables and cinnamon, is particularly dangerous to children, and exposures from food, paint and other elements of the environment have been linked to diminshed brain development, lower IQs, cardiovascular disease and higher rates of cancer, according to the Environmental Defense Fund. Studies suggest that cadmium can increase the risk of both cardiovascular and kidney disease as well as cancer.
How do heavy metals get into chocolate?
These metals pollute the environment, including the soil, in many parts of the world. Metals — especially cadmium and lead — in contaminated soil can find their way into the plant itself through the roots. The toxic metals reach our bodies when we eat products made from those plants, including chocolate made from the cacao plant, Tewodros Godebo, assistant professor of environmental health sciences at Tulane University and lead author of the new study, tells Yahoo Life.
And the more cacao that’s in a specific chocolate — which makes it darker — the more likely it is to contain heavy metals. “Elements like cadmium are mostly associated with high cacao chocolates coming from [plants grown in] South and Central American countries [while] West African countries like Ivory Coast and Ghana have lower doses of cadmium,” says Godebo.
What did the new study find?
Godebo and his colleagues tested 155 store-bought milk and dark chocolates for 16 different heavy metals (including both toxic and beneficial). Their analysis found just four dark chocolate bars that contained concerning levels of cadmium. It’s important to note, however, that the researchers used a different standard, comparing the levels of metals to the international limits and the limits proposed by the U.S. Environmental Protection Agency, rather than Califonia’s standards, which are the strictest in the nation.
Still, “the important assessment we did was if children or adults [were] consuming one ounce of chocolate daily, which is close to the daily consumption of chocolate, only children exceeded the hazard quotient,” says Godebo.
The researchers found that an ounce of any of the four dark chocolate bars they analyzed did not contain enough heavy metal to pose a danger to adults, but could to young children. Godebo says that if children ate an ounce of dark chocolate a day, they would be consuming two or three chocolate bars a week (for comparison, Lindt chocolate bars are mostly 3.5 oz). So it’s unlikely that a 3-year-old — the assessment was based on the average weight of a child of that age — would consume more than that in a week. “So the risk is even more minimized,” Godebo adds.
For adults, there was no meaningful risk. That’s because their larger bodies are better equipped to get rid of heavy metals compared to kids, says Le. It's also worth noting that the dark chocolate bars were rich in healthy nutrients, including zinc, copper, iron and magnesium; some of the chocolates tested contained more than 50% of the daily requirements of these minerals for adults.
But “dark chocolate for children on a long-term basis should still be avoided, especially in the early years, as the effects of consuming heavy metals can accumulate,” says Le. “Children are less likely to benefit from the compounds found in dark chocolate.”
Adults, on the other hand, should feel free to go ahead and enjoy. “Here, the benefits of consuming dark chocolate outweigh the risk," Le says, "especially as adults reach their older years and the flavonols in dark chocolate can help improve cognitive function and gut health.”