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.
“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.
Just 1 Serving of Dark Chocolate May Exceed Recommended Cadmium Levels
Compared with other types of chocolate and sweets, experts consider dark chocolate to be healthy. It has lower added fat and sugar, and contains beneficial antioxidants called flavonoids that are good for the heart and overall health.
It’s potentially worrisome that for some of the products, a single serving — which for dark chocolate could be just 30 grams (g) — may already exceed these reference values for lead and cadmium, says Katarzyna Kordas, PhD, an associate professor in the departments of epidemiology and environmental health at the University at Buffalo, who was not involved in the study.
“On the flip side, since we do not know what types of chocolate products were tested in this study (with the exception of dark chocolate), we have no idea about the products or the actual serving sizes,” says Dr. Kordas.
“Consumers should be alarmed that experts other than the U.S. Food and Drug Administration (FDA) are the first to identify these problems,” says Jerold Mande, MPH, an adjunct professor of nutrition at the Harvard T.H. Chan School of Public Health in Cambridge, Massachusetts, who was not involved in the study.
Unfortunately, the study report doesn’t include specific products and names, which doesn’t really help people figure out how to buy cocoa products with lower levels of heavy metals, says Mande.
Recently, Consumer Reports measured the amounts of heavy metals in 28 different dark chocolate bars, and that analysis did contain brand names, he says.
Heavy Metal Levels Decreased in the Later Years of the Study
For over 50 to 65 percent of the products, the levels of lead and cadmium were below the stringent reference values cited in California’s Proposition 65, says Kordas.
“Furthermore, levels of all three metals were lower in later years of the study than in earlier years. That could potentially mean that food contamination is going down,” she says.
Based on these findings, though, it’s still unclear whether the average person should be alarmed or change their behavior, says Kordas. This study and others like it leave many questions unanswered, she adds.
For instance, she says, how much do lead and cadmium from chocolate contribute to heavy metals in the human body, and do they result in any health effects?
“Unfortunately, we do not have answers to these questions, and the answers are likely to be complicated by [additional questions like]: How much chocolate is consumed by individuals? Is it milk or dark chocolate? Is it consumed after a meal or as a snack to stave off hunger? All those factors matter,” says Kordas.
What Are the Health Risks of Cadmium and Lead?
“Metals occur in cocoa products because, depending on field conditions and location, they may be incorporated into cocoa beans from soil or water as the plants grow. Contamination could also occur during the manufacturing process,” says Kordas.
Cocoa isn’t the only food that contains cadmium. Humans are exposed to small amounts of cadmium through a variety of foods, such as shellfish, lettuce, potatoes, and mushrooms.
Cadmium can cause vomiting and diarrhea when ingested, while inhalation can cause kidney damage, fragile bones, and certain cancers.
Although lead has been banned in gasoline and paints in the United States, it’s still used in metal mixtures and industrial products, including ammunition, older pipes, car radiators, glass, and pottery.
While lead exposure is associated with health risks at any age, young children are the most vulnerable and can suffer developmental and cognitive problems from lead exposure.
Consumers have the right to demand foods that are as low in contaminants as possible, and some products are clearly better than others when it comes to heavy metal content, says Kordas.
“As we live in an increasingly contaminated world, a completely ‘pure’ food may be a myth,” she says.
