Chocolate is one of the most popular and beloved treats around the world. Over 7 million tons of chocolate are produced globally each year (1). However, there has been concern in recent years about the levels of heavy metals, such as lead and cadmium, found in chocolate. This article will examine the current evidence on heavy metal levels in chocolate and evaluate whether or not chocolate is considered high in heavy metals.
What are Heavy Metals?
Heavy metals are metals with high atomic weight and density compared to water (2). The four main heavy metals of concern related to food are lead, cadmium, arsenic, and mercury. Even small amounts of these metals can be toxic to the human body when consumed over time. Young children are especially vulnerable to the neurological effects of heavy metal toxicity (3).
Some heavy metals like zinc, copper, chromium, iron, and manganese are necessary for good health at low levels, but become toxic at higher intakes. Other heavy metals like lead, cadmium, arsenic, and mercury are toxic even at very low levels of exposure.
Exposure to heavy metals can occur through consumption of contaminated food, water, or products. Industrial pollution is a major source of environmental heavy metal contamination that can make its way into the food supply (4).
How Could Heavy Metals Get into Chocolate?
The cocoa bean is the raw ingredient that chocolate is made from. Cocoa trees absorb minerals from the soil, including heavy metals if the soil contains elevated levels. Therefore, the first potential source of heavy metals in chocolate is contamination of the soil where cocoa trees are grown (5).
Certain regions of the world, such as parts of Africa and Asia, have higher natural levels of cadmium in the soil. Farming practices like the improper use of phosphate fertilizers or sewage sludge can further increase levels of cadmium and other metals in soils (6).
During processing and manufacturing, chocolate could become contaminated through metals leaching from industrial equipment and storage containers. Low quality manufacturing processes that do not follow food safety guidelines could also introduce metals into chocolate products (7).
Finally, heavy metals could make their way into finished chocolate products through ingredients added to make milk chocolate, candy bars, chocolate spreads, etc. For example, milk can contain small amounts of lead and arsenic from cattle feed and environmental sources (8).
Lead in Chocolate
Several studies have detected concerning levels of lead in some chocolate products:
- A Consumer Reports study found lead in 24 out of 28 dark chocolate bars tested, with levels up to 0.4 mcg per serving. Trader Joe’s dark chocolate had the highest average lead level at 0.17 mcg per serving (9).
- Research on 50 European chocolate products found 0.035 mg/kg lead on average, with values ranging from 0.005 to 0.200 mg/kg. The 0.2 mg/kg maximum is the European regulatory limit for lead in chocolate (10).
- Analysis of 120 chocolate samples from different regions of India showed an average lead concentration of 1.83 mg/kg. 33% of samples exceeded India’s lead limit of 2.5 mg/kg in chocolate (11).
While no amount of lead exposure is considered safe, the FDA limit for lead in candy likely to be consumed frequently by small children is 0.1 mcg per serving (12). The studies above suggest that chocolate can sometimes exceed this guidance level. Overall though, chocolate is not considered one of the highest sources of lead in the average person’s diet.
Cadmium in Chocolate
Several studies have also detected cadmium in chocolate:
- Testing by Consumer Reports found an average of 0.121 mcg cadmium per serving in the 28 chocolate bars analyzed. Cadmium levels ranged from 0 to 0.365 mcg per serving (9).
- Analysis of 74 chocolate products sold in Canada showed an average cadmium concentration of 0.087 mg/kg. Only 4% of products exceeded Canada’s limit of 0.5 mg cadmium per kg of chocolate (13).
- Research on 50 chocolate products in Europe detected an average cadmium level of 0.080 mg/kg. Only 8% of samples were above the EU limit of 0.1 mg/kg cadmium permitted in chocolate (10).
The Joint FAO/WHO Expert Committee on Food Additives has established a tolerable monthly intake for cadmium of 25 mcg/kg of body weight (14). At the levels found in chocolate, regular consumption is unlikely to result in exceeding this limit for most people. However, as cadmium can accumulate in the body, those eating higher amounts of chocolate should monitor their overall cadmium exposure.
Arsenic and Mercury in Chocolate
A few studies have also looked at arsenic and mercury concentrations in chocolate products:
- The Consumer Reports testing found arsenic levels ranging from 0 to 1.4 mcg per serving in the 28 chocolate bars tested, with an average of 0.25 mcg. Trader Joe’s dark chocolate had the highest average arsenic level at 0.411 mcg per serving (9).
- Research on Indian chocolates detected total arsenic levels between 0.018 to 1.804 mg/kg. The average of 0.442 mg/kg was concerningly high compared to the recommended limit of 0.1 mg/kg (11).
- Analysis of lead and cadmium in 50 European chocolates also reported an average mercury concentration of 0.005 mg/kg, below the 0.1 mg/kg European limit (10).
The data is limited, but it appears that for most major chocolate brands, arsenic and mercury levels are not of immediate health concern. However, testing has revealed high arsenic in some products, indicating that contamination does occur sporadically.
Do Heavy Metal Levels Vary Between Chocolate Types?
Studies indicate that heavy metal concentrations can differ depending on chocolate type:
- Dark chocolate has been found to have higher cadmium and lead levels than milk chocolate (9, 10).
- Cocoa powder can contain higher cadmium than chocolate bars. Cadmium levels are also higher in Dutch processed/alkalized cocoa powder (15).
- Unsweetened chocolate has higher cadmium content compared to chocolate bars and milk chocolate. This may be due to low dilution of cadmium from sugars and fats (16).
- White chocolate does not contain cocoa solids, so it generally has very low levels of heavy metals (17).
The higher cocoa content of dark chocolate means less dilution of any heavy metals present in the cocoa beans themselves. Cocoa powder is even more concentrated than bars. So products with higher proportions of pure cocoa tend to test higher in cadmium and lead.
Do Organic Chocolates Have Less Heavy Metals?
Some studies have compared heavy metal levels in organic versus conventional chocolates:
- Analysis of lead and cadmium content in 74 chocolate products in Canada found no significant differences between conventional and certified organic chocolates (13).
- However, a study in Poland found somewhat lower cadmium levels in organic chocolate bars compared to conventional bars (0.09 vs. 0.12 mg/kg) (18).
While more research is needed, these results suggest organic production methods may not guarantee lower heavy metal levels in chocolate. Since cocoa trees readily absorb cadmium from the soil, contamination could occur even with organic farming if the soil naturally contains elevated cadmium levels.
Are Heavy Metal Levels in Chocolate Increasing?
Given ongoing environmental pollution, there has been some concern that heavy metal contamination in food is increasing over time. However, research shows little evidence that metals levels in chocolate are rising:
- A comparison of studies from 1993 to 2013 found no significant increase in lead or cadmium concentrations in chocolate (10).
- Analysis of cadmium levels in 74 chocolate products from Canada did not show increases compared to older data (13).
Enhanced quality control measures in cocoa farming and chocolate manufacturing may be keeping pace with environmental heavy metal loads. This data indicates cadmium and lead levels have not substantially increased in chocolate over the past few decades.
Health Risks of Heavy Metals in Chocolate
The dose makes the poison – even potentially toxic heavy metals may not cause harm if the exposure level is low enough. But what are the health implications of long-term consumption of chocolate containing small amounts of cadmium and lead?
- Lead: Build up of lead in the body over years can contribute to neurological deficits, kidney damage, impaired fertility, and problems with memory and concentration (3).
- Cadmium: Kidney damage from cadmium occurs at chronic daily intakes above the maximum safe limit. There are also possible impacts on bones and the cardiovascular system (14).
- Arsenic: The inorganic form of arsenic found in food is a carcinogen. Long-term exposure through contaminated food or water increases cancer risks (19).
However, chocolate and cocoa products make up a very small portion of total dietary exposure to these metals. At the levels currently found in most chocolates, consumption does not contribute significantly to reaching toxic thresholds of heavy metal intake.
To put this in perspective, a 50 g serving of dark chocolate containing 0.2 mg/kg cadmium adds only 0.01 mcg cadmium to your diet. Compare this to the 25 mcg per month tolerable limit. Even daily chocolate consumption would require very high cadmium levels to exceed safe intake guidelines.
Ways to Limit Heavy Metal Exposure from Chocolate
While chocolate is not a major heavy metal hazard at current contamination levels, those who consume chocolate regularly may want to take precautions. Here are some tips to minimize exposure for adults and children:
- Choose milk or white chocolate more often, as these have lower metals than dark varieties.
- Enjoy smaller portions of dark chocolate to limit cadmium and lead intake.
- Avoid chocolate products made with excessively high cocoa percentages.
- Consume a variety of treats instead of chocolate every day.
- Vary treats eaten by children – do not constantly give the same brand of chocolate.
- Avoid artisanal chocolates made in regions with high soil cadmium.
- Consider choosing chocolates tested to be low in metals.
Testing products and limiting intake of higher cadmium varieties can minimize potential risks. But there is no need to completely avoid chocolate due to heavy metals. As part of a varied diet, enjoying moderate amounts of chocolate remains safe for most people.
Conclusion
Chocolate does contain measurable levels of heavy metals like cadmium and lead. However, concentrations in most popular commercial chocolates are not at levels of immediate health concern for average consumers. Dark chocolate tends to have higher metals content than milk or white varieties. But evidence does not indicate heavy metal concentrations in chocolate are increasing over time. Eating a couple small squares of chocolate a day as part of a overall healthy diet poses little risk from cadmium or lead. While screening and limits on metals in chocolate ingredients remain important, there is no reason to refrain from indulging in moderate chocolate consumption.