43% of Dark Chocolates Exceeded Safety Limits for Lead in New Study (2024)

New testing shows that almost half of the dark chocolate products evaluated contain heavy metals, including lead and cadmium. Since some of the worst offenders were organic products, researchers are trying to determine how significant the heavy metal contamination actually is and what’s safe for people to consume.

Heavy metals can enter the food supply through pathways like contaminated soil and water. That’s because these pollutants tend to originate from industrial processes, mining activities, or agricultural practices using certain fertilizers and pesticides.

In the case of cacao, a main ingredient in dark chocolate, “there are reports of metal polluting industries that are situated next to cacao plants. Cacao then becomes contaminated during a certain stage of its creation—its drying process—and makes its way into the [chocolate] bar from there,” study first author Jacob Hands, a medical student at the George Washington University School of Medicine and Health Science, told Verywell.

Consumption of heavy metals at certain levels may be linked to health issues like neurological damage. For pregnant people, elevated exposure to certain heavy metals may be linked to an increased risk of birth defects.

To gauge the pervasiveness of this heavy metal contamination over time, researchers analyzed 72 consumer dark chocolate and cocoa-containing products for contamination with lead, cadmium, and arsenic sourced from four different years: 2014, 2016, 2019, and 2022.

The analysis showed that:

• 43% of the products exceeded the maximum allowable dose levels for lead set by California’s Proposition 65
• 35% of the products exceeded the maximum allowable dose levels for cadmium set by Proposition 65
• 0% of the products exceeded the maximum allowable dose levels for arsenic set by Proposition 65

However, across all chocolates tested, the median concentration (middle value of all detected values) of each metal was lower than even the strictest Proposition 65 limits, indicating some of the chocolates tested are outliers with especially strong metal concentrations.

Surprisingly, chocolates marketed as “organic” products were significantly more likely to demonstrate higher levels of both cadmium and lead versus non-organic chocolate.

This analysis also showed that heavy metal contamination in chocolate is getting better over time; levels decreased between 2014 and 2022.

Should You Avoid Dark Chocolate Because of Heavy Metal Concerns?

The authors of this study note that the risk of heavy metal exposure from just one serving of dark chocolate is low.

But eating more than one serving per day or combining these products with other food sources of heavy metals could lead to higher overall exposure.Some of those foods include:

• Root vegetables, such as carrots and potatoes, may contain small amounts of lead and cadmium from contaminated soil or water.
• Starchy foods like rice and grains may contain cadmium, especially if they were grown in areas with high levels of pollution or contaminated water.
• Certain types of fish, like tuna, can also have trace amounts of metals.

“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,” study principal investigator Leigh Frame, PhD, Executive Director of the Office of Integrative Medicine and Health at the George Washington University, told Verywell.

Starches and root vegetables—which tend to be starches themselves—are nutritious parts of a balanced diet. You don’t need to cut them out because of trace amounts of heavy metals. But a one-serving limit per day is still best for another reason: Too much starch can lead to unhealthy spikes in blood sugar.

As for tuna and other fish that may contain heavy metals, the FDA recommends sticking to no more than two to three servings of canned light tuna per week. If you prefer Albacore or white tuna, stick to just one serving per week, as this type has higher mercury levels. While the FDA’s tuna-eating guidelines were mostly designed for kids and people who might become pregnant, it’s an easy guideline for most people to follow. The FDA also offers guidance on other types of fish and recommends safe weekly limits if you want to include them in your diet.

The serving size for chocolate depends on the brand and form, but you can usually get a sense of a portion based on the weight. Many popular candy brands offer a range of dark chocolates with varying amounts of cacao (shown as a percent).

Here’s an example of what is considered one serving of some popular dark chocolate treats:

• 3 (36 grams) Lindor 60% Dark Chocolate Truffles
• 3 (32 grams) Ghiradelli 72% Cacao Dark Chocolate Squares
• 4 pieces (30 grams) of a Hershey’s Special Dark chocolate bar

“Despite containing heavy metals, dark chocolate can offer health benefits when enjoyed in moderation,” Julie Pace, RDN, a Mississippi-based registered dietitian nutritionist, told Verywell. “It’s packed with antioxidants—especially flavonoids—that may promote heart health, enhance blood flow, and improve mood.”

Pace said pairing chocolate with a healthy snack, like nuts or fruit, can also help you limit your portion while still feeling satisfied. If that’s not the case and your craving is too strong, “consider incorporating other foods rich in magnesium, like nuts and seeds, which might help reduce chocolate cravings naturally,” she said.

Are Certain Populations More At-Risk?

Certain groups are more at risk when exposed to heavy metals due to a variety of factors, including age, health status, and lifestyle.

Children are particularly vulnerable to side effects of heavy metals because their developing bodies can absorb them more readily. Plus, smaller body size means they can experience higher concentrations of toxic substances.

Pregnant people also face increased risks, as heavy metal exposure can adversely affect fetal development.

Individuals with compromised immune systems or preexisting health conditions may be more susceptible to the harmful effects of heavy metals, too.