How Does Cadmium Get Into Chocolate?

December 12, 2025 •

4 min read

According to the U.S. Food and Drug Administration (FDA), chocolate is known to sometimes contain cadmium and lead from environmental origins. The key reason for this is that cacao plants, the source of chocolate, readily absorb cadmium from the soil as they grow. This heavy metal then accumulates in the cocoa beans, which are eventually processed into chocolate.

Quick Summary

Cadmium gets into chocolate through the natural absorption of the heavy metal by cacao plants from the soil during their growth. The contamination source is rooted in the geology and composition of the soil, not in post-harvest handling. Higher cacao content, like in dark chocolate, can result in higher cadmium levels.

Key Points

Soil is the Primary Pathway: Cadmium enters cacao plants by absorption through their root systems from the soil, especially in regions with volcanic geology.
Dark Chocolate Contains Higher Levels: Due to its higher concentration of cocoa solids, dark chocolate typically contains more cadmium than milk chocolate.
Soil Chemistry Plays a Role: Acidic soils increase the bioavailability of cadmium, making it more readily available for uptake by cacao plants.
Genetic Selection Is a Long-Term Solution: The chocolate industry is exploring and breeding cacao genotypes that are low-cadmium accumulators to address the issue at the source.
Post-Harvest Techniques Help: Processing methods such as optimized fermentation, efficient winnowing, and bean blending can effectively reduce the final cadmium content in chocolate products.
Regulation Drives Mitigation: Global and regional regulations, like those in the EU, are setting limits and encouraging the industry to adopt mitigation strategies.

The Primary Source: Soil Absorption

The fundamental way cadmium gets into chocolate is through the soil in which the cacao trees grow. Unlike lead, which often contaminates beans after harvesting, cadmium is a geogenic contaminant, meaning it comes from the earth itself. The cacao tree's root system is particularly effective at absorbing this heavy metal from the ground, which then travels up through the plant and accumulates in the seeds, or cocoa beans.

Factors Influencing Cadmium Uptake

Several environmental and agricultural factors play a role in how much cadmium a cacao plant absorbs:

Soil Composition: Volcanic soils, common in many parts of Latin America where cacao is grown, are naturally richer in cadmium. The weathering of rocks and volcanic eruptions introduce the element into the soil.
Soil pH: The acidity of the soil is a major determinant of cadmium availability. More acidic soils allow cadmium to be more soluble and easily absorbed by the plants. Higher soil pH reduces cadmium solubility and uptake.
Fertilizers: Some phosphate fertilizers contain trace amounts of cadmium. While not the sole source, long-term use can contribute to cadmium buildup in the soil over time.
Plant Age: As cacao trees age, the concentration of cadmium tends to increase within the plant. Older trees may have higher levels of the heavy metal.
Genetic Variation: Some cacao genotypes are more efficient at absorbing and accumulating cadmium than others, even when grown in the same soil. Research is focused on identifying and breeding low-cadmium accumulator genotypes.

Impact of Chocolate Type and Processing

The concentration of cadmium in the final chocolate product is directly related to the amount of cocoa solids used. Dark chocolate, which contains a higher percentage of cocoa, tends to have higher levels of cadmium than milk chocolate. This is because the milk and sugar in milk chocolate effectively dilute the total cadmium concentration. Post-harvest processing techniques can also influence the final levels.

How Post-Harvest Steps Affect Cadmium

Fermentation: Research shows that the fermentation process can influence cadmium levels. Specifically, when beans are fermented to a lower pH (<5), cadmium can migrate from the cocoa nib (the main part used for chocolate) to the testa (the outer shell), which is later discarded.
Blending: Manufacturers can blend beans from different regions with varying cadmium levels to achieve a final product that meets safety limits. Beans from West Africa generally have lower cadmium levels than those from some parts of Latin America.
Winnowing: This process separates the nibs from the outer shell (testa). Since the testa can hold more cadmium in some cases, efficient winnowing can reduce the final cadmium content.

Cadmium vs. Lead Contamination: A Comparison


Aspect	Cadmium	Lead
Primary Source	Cacao tree absorption from soil during growth.	Post-harvest contamination from dust, soil, and fumes.
Mechanism	The plant's root system draws cadmium from the ground, which then accumulates in the beans.	Lead particles stick to the sticky outer surface of the beans during fermentation and drying.
Contamination Stage	Pre-harvest, occurring throughout the tree's lifespan.	Post-harvest, mainly during drying and fermentation.
Mitigation Strategy	Long-term solutions: soil management, genetic selection, and replacing older trees.	Shorter-term solutions: cleaner harvesting, drying away from roads, and thorough bean washing.
Regional Variation	Latin American cocoa often has higher levels due to volcanic soil.	Dependent on local air quality and harvesting practices.

Regulation and Mitigation Efforts

In response to consumer concerns, regulatory bodies and the chocolate industry are actively working on solutions. The European Union has set maximum limits for cadmium in chocolate products, based on their cocoa content. In the US, organizations like Consumer Reports have published findings on cadmium levels in various brands, prompting industry action.

Mitigation strategies include:

Agronomic Practices: Farmers can use soil amendments like limestone to increase pH and reduce cadmium bioavailability. Adding nutrients like zinc and manganese can also help, as they compete with cadmium for absorption.
Genetic Selection: Breeding programs are developing cacao varieties that are naturally lower accumulators of cadmium.
Post-Harvest Improvements: Better processing techniques, including controlled fermentation and meticulous winnowing, can help remove cadmium. Blending beans is also a key strategy.

Conclusion

The presence of cadmium in chocolate is a complex issue stemming primarily from the natural bioaccumulation of the heavy metal from certain soil types by cacao plants. While higher levels are often found in dark chocolate due to a higher concentration of cocoa solids, the industry is increasingly focused on developing sustainable and safe practices. Through improved soil management, genetic research, advanced processing, and bean blending, chocolate manufacturers can continue to provide safe products for consumers. Ultimately, understanding the source and mechanisms behind cadmium contamination allows for more informed choices and supports the long-term health of both consumers and the chocolate industry.

Key Takeaways

Soil is the Source: Cadmium contamination in chocolate begins in the soil where cacao trees are grown, as the plants naturally absorb the heavy metal.
Geographic Variations: Soil composition, particularly in volcanic regions common to Latin America, influences the amount of cadmium present in cacao beans.
Dark Chocolate Has More: Products with a higher percentage of cocoa solids, such as dark chocolate, generally contain higher levels of cadmium.
Mitigation is Possible: Strategies like soil amendments, selective breeding of cacao plants, and post-harvest techniques like blending and optimized fermentation can reduce cadmium levels.
Industry Standards: Regulatory bodies like the European Union have set maximum allowable levels for cadmium, and consumer awareness campaigns have spurred industry action.

Frequently Asked Questions

Dark chocolate contains a higher concentration of cocoa solids compared to milk chocolate. Since cadmium accumulates in the cocoa beans, and not in milk or sugar, a higher percentage of cocoa means a higher concentration of potential cadmium.

High cadmium levels in soil often originate from geogenic sources, such as the weathering of rocks and volcanic activity. This is a natural phenomenon, and certain cocoa-growing regions, particularly in parts of Latin America, are affected.

Yes, organic chocolate can still contain cadmium. Since the cadmium is absorbed from the soil and is naturally occurring, organic farming practices do not prevent its uptake by the plant. In fact, some studies have found slightly higher levels in organic products, potentially due to sourcing from specific regions.

Yes, regulatory bodies around the world have established maximum limits. The European Union, for example, has set varying limits based on the cocoa content of the product. The FDA also monitors levels and has established interim reference levels for potential health concerns.

Producers are implementing several strategies, including mapping soil to find low-cadmium areas, breeding cacao plants that absorb less cadmium, and using soil amendments to alter pH. Post-harvest, techniques like controlled fermentation and blending beans also help reduce levels.

No, concerns about heavy metals in chocolate have existed for decades, with studies and testing conducted since at least the mid-2000s. Increased consumer awareness and stricter regulations have brought the issue into sharper focus more recently.

For most people, enjoying dark chocolate in moderation is not a significant health risk. Health experts often recommend a varied diet to minimize exposure to any one contaminant. Consumers can also choose brands that test for and report low levels of heavy metals.