A recent study has revealed the presence of lead and cadmium, two toxic metals known to be linked to a range of health issues including cancer and developmental problems, in dark chocolate and other cocoa-based products. These metals are naturally occurring elements in the Earth's crust and find their way into the soil where crops are cultivated, making their presence in food items, unfortunately, inevitable. However, certain agricultural practices and environmental pollution can lead to higher concentrations of these metals in certain regions.

Surprisingly, the research indicated that organic dark chocolates, which are typically grown with fewer synthetic pesticides and contaminants, were found to contain some of the highest levels of these harmful metals. This contradicts the common belief that organic products are inherently safer. Dark chocolate is widely recognized for its rich content of flavonoids, antioxidants, and beneficial minerals, which are associated with numerous health benefits such as improved heart health, enhanced cognitive function, and reduced chronic inflammation.

The study, published in the Frontiers in Nutrition journal, focused exclusively on pure dark chocolate products, which contain the highest concentration of cacao—the raw, unroasted form of the cacao bean. Products that included additional ingredients, such as candies or baking chocolates, were not considered in this research. The identities of the specific products and manufacturers tested were not disclosed to maintain the study's impartiality.

Jane Houlihan, the national director of science and health for Healthy Babies Bright Futures—an organization dedicated to minimizing children's exposure to neurotoxic chemicals—commented on the findings, stating that "the average levels of lead and cadmium in cocoa-containing products in the new study are at or above the average amounts the US Food and Drug Administration finds for lead and cadmium in the most highly contaminated foods they test."

According to the FDA, baby food sweet potatoes, baby food teething biscuits, sandwich cookies, white wine, and ranch dressing are among the foods most contaminated with lead. Meanwhile, sunflower seeds, spinach, potato chips, leaf lettuce, and french fries are known to contain the highest levels of cadmium.  emphasized that the typical health risks associated with consuming chocolate are generally below the federal government's official safe thresholds, mainly because people tend to consume chocolate in small quantities.

However, she warned that there could be heightened risks for young children, pregnant women, and individuals who consume chocolate regularly, particularly dark chocolate. The National Confectioners Association, representing the chocolate industry, assured consumers that "chocolate and cocoa are safe to eat and can be enjoyed as treats as they have been for centuries. Food safety and product quality remain our highest priorities, and we remain dedicated to being transparent and socially responsible."

The study analyzed 72 consumer cocoa products for the presence of lead, cadmium, and arsenic over an eight-year period, from 2014 to 2020. This longitudinal approach provided a more comprehensive understanding of the issue compared to previous studies that only examined chocolate at a single point in time. The testing was conducted by Consumer Labs, a non-profit organization known for its third-party testing of health and nutrition products, which sent samples to various laboratories to ensure accuracy.

The results showed that 43% of the chocolate products tested exceeded the maximum allowable dose level for lead as set by California’s Proposition 65, while 35% exceeded the same standard for cadmium. No significant levels of arsenic were detected in the products. It is important to note that Proposition 65's limits are more stringent than those set by the federal government. For instance, the FDA allows a maximum of 0.1 parts per million of lead in children's candy, whereas California’s Proposition 65 has a safety standard of 0.05 parts per million for chocolate.

Danielle Fugere, president and chief counsel for As You Sow, a non-profit focused on shareholder advocacy, explained the significance of Proposition 65's standards, saying, "Proposition 65 sets a protective level which allows consumers to make a rational choice and say, 'OK, how much do I want?'" She added that there are many sources of lead, including water, vegetables, fruits, soil, dust, and air, and that each individual must make their own decision about whether they feel comfortable consuming chocolate that may contain lead.

Leigh Frame, the senior study author and executive director of the Office of Integrative Medicine and Health at George Washington University, advised that healthy adults who consume chocolate in moderation should not be overly concerned. She stated, "A typical serving of dark chocolate is 1 ounce, so eating 1 ounce every day or so is a pretty small risk in the grand scheme of things. But it’s something we need to be aware of in case we are also around other sources of lead exposure, such as lead paint in an old home."

However, the risk of heavy metal exposure increases for certain vulnerable populations, such as those who are medically compromised, pregnant, or young children, according to Tewodros Godebo, an assistant professor of environmental geochemistry at Tulane University School of Public Health and Tropical Medicine. He noted that over time, the consumption of even low levels of cadmium can lead to kidney damage, and the Environmental Protection Agency classifies the metal as a probable human carcinogen.

Godebo, who was not involved in the study, highlighted the particular risks for sensitive individuals, such as those with kidney disease who may not be able to efficiently eliminate metals from their bodies, and for pregnant women who are protecting the developing fetus. Children, in particular, can absorb a significant amount of ingested lead, with absorption rates of about 50% after a meal and up to 100% on an empty stomach. The World Health Organization states that there is no safe level of lead, especially for children, as it can adversely affect brain development, leading to reduced IQ, behavioral changes, and lower educational achievements.

Nevertheless, for healthy adults, Godebo's risk analysis suggests that the occasional indulgence in 1 ounce of dark chocolate is not a significant cause for concern. He concluded, "Of course, we want close to zero exposure, but that's impossible. Everything we eat likely contains some level of these contaminants. But it is a relative risk."