New study confirms concerning heavy metal contamination in cocoa

A ​new study​ from George Washington (GW) University finds a concerning number of cocoa products in the US contain excessive levels of heavy metals. Organic cocoa products are the worst offenders, with concentrations that surpass recommended guidelines.

The global chocolate industry is expected to bring in $133.60 billion (€121.9 bn) in revenue in 2024, with most of this coming from the US, totalling $23,210 million, Statista data shows​. Dark chocolate is the fastest-growing segment in chocolate around the world, data insights from Mordor Intelligence ​show. Predictions put its compound annual growth rate (CAGR) between 2024 and 2030 at 5.48%.

Now, these new scientific findings risk dampening the US chocolate and cocoa industry sales, particularly dark chocolate.

The study, published on July 31 in the Frontiers in Nutrition journal, saw researchers from GW University analyze cocoa-containing confectionery sold in the US over eight years. Following their results, the study’s authors recommend dark chocolate enthusiasts limit their daily intake to one ounce.

Finding metal in chocolate​

Researchers analyzed 72 consumer cocoa products every other year over eight years. They studied samples, which included dark chocolate, to look for contamination of lead, cadmium or arsenic. In high amounts, these heavy metals pose a significant health risk to consumers.

“We all love chocolate, but it’s important to indulge with moderation as with other foods that contain heavy metals, including large fish like tuna and unwashed brown rice,” says Leigh Frame, director of integrative medicine and associate professor of clinical research and leadership at the GW School of Medicine and Health Sciences.

For many consumers, it’s not easy to remove heavy metals from our diets as they’re contained in numerous food items. Yet, what the researchers of this latest study recommend is that it’s possible to be aware of foods that contain heavy metals and monitor consumption of these. “While it’s not practical to avoid heavy metals in your food entirely, you must be cautious of what you are eating and how much,” Frame adds.

The GW University scientists established a maximum acceptable dose limit to determine the amount of heavy metals in cocoa. They applied this to various chocolate products available for purchase at grocery stores.

Out of the 72 cocoa items assessed, 43% exceeded the maximum allowable dose level for lead, and 35% exceeded this level for cadmium. None of the products studied, however, exceeded the maximum allowable dose level for arsenic. In a surprise finding for the researchers, organic-labelled products had higher levels of both lead and cadmium compared to non-organic products.

Understanding our fears: An eight-year investigation​

Despite this new research, concerns that heavy metals may exist in confectionery products are not new.​ “We have known about potential heavy metal contamination in cocoa and dark chocolate for some years,” says Jacob Hands, the study’s lead author and a medical student researcher at the George Washington University School of Medicine and Health Sciences.

Beyond confirming whether their suspicions were correct, the eight-year research project has always focused on consumer health. “We were interested in looking at whether or not these levels could be meaningful from a public health standpoint,” Hands adds.

If researchers’ concerns were present, some might ask why conducting their study over eight years was so important rather than opt for a shorter time frame between their research concept and results. The answer lies in the way heavy metals behave in confectionery. “Changes over time are key,” says Hands.

Drawing on the history of other food groups, the study’s lead author felt understanding the impact heavy metal has or could have in confectionery needed to be done over time. Taking the example of supplements, Hands says these generally used to be far more contaminated than they are today, due to “a raft of enhanced oversight and consumer interest groups”. “Therefore, to really make sense of this topic, we have to plot its progress or lack thereof,” Hands says.

In the case of confectionery, fast routes to market are commonplace, leading to a wide range of new products entering the industry every year. “Companies have gotten a lot better at limiting lead in their products over time,” Hands adds.

The multi-year study also explains how these heavy metals found their way into cocoa products. “Often, these levels arise from post-harvesting contamination,” Hands confirms. For example, there are reports of other metal-polluting industries located next to cacao plants. Thus, cacao becomes contaminated during a particular stage of its creation – its drying process – and makes its way into the bar from there.

Is cocoa safe?​

Following the research team’s findings, many consumers may question whether they should avoid cocoa products. For a sector that is continuing to battle rising raw material costs and reduced production volumes, this could be disastrous for manufacturers and brands that have already been looking for ways to manage the cocoa crisis.

 “Dark chocolate consumption is still, on average, quite safe,” says Hands. Consumers should just be aware that certain brands may expose them to potentially biologically significant levels of certain heavy metals like cadmium,” Hands adds. However, it’s unclear how significant its consumption would be at this level.

For consumers who want to avoid metals, consumer interest groups like ​Consumer Labs​ and consumer reports exist to ensure that they’re not consuming heavy metals when enjoying their favourite chocolate products.

After eight long research years to prove their theory, scientists behind the findings hope to see the cocoa industry become aware of the problem. They hope they strive to protect consumers from heavy metals and not treat it as an oversight.

 “I doubt most companies even know that their chocolate is contaminated to any serious degree,” says Hands. “Understanding and having an honest and direct conversation about risk and how to mitigate the introduction of metals from their resource sites is advisable.” Hands adds.

Source: ​Hands JM, Anderson ML, Cooperman T, Balsky JE and Frame LA (2024) A multi-year heavy metal analysis of 72 dark chocolate and cocoa products in the USA. Front. Nutr​. 11:1366231. doi: 10.3389/fnut.2024.1366231