Cadmium and Lead in Dark Chocolate—How Dangerous?

News

Feb 7

Report by The Food Co-op Product Research Committee

Many of us have heard that Consumer Reports has tested dark chocolate bars sold in the US and found that most had higher levels of cadmium and lead than the maximum levels set by California. This new report is very frustrating, since we’ve been told for years that dark chocolate is good for us because it is high in antioxidants. Once again, we are told something is good (or bad) for us and then later on we’re told it is actually bad (or good) for us. While exasperating, such inconsistency is not really surprising, since scientific knowledge is constantly evolving as new studies and experiments are conducted. But it does make it hard to know what we should and shouldn’t eat.

So, what should we do about chocolate? The short answer is that if you are a healthy adult, eating dark chocolate in moderation should not be a problem. Children, pregnant women, and people with kidney or bone issues should probably avoid dark chocolate. Luckily, children generally prefer milk chocolate, which has less cadmium and lead because it contains less cocoa. As always, the best diet is a varied one of fresh foods, each food eaten in moderation. Chocolate is only one of many foods that are both good and bad for us—even kale should not be eaten in large quantities every day!

Now the long answer.

Cadmium occurs naturally in the soil, particularly volcanic soil or where there have been forest fires. Cocoa trees are not the only plants that take up cadmium, so many of the foods we eat have it—vegetables (including spinach), cereal products, nuts, starchy roots like potatoes, meat, bivalve mollusks, and even wild mushrooms. So, while too much cadmium poses a health risk, it cannot be avoided altogether. However, women who are considering becoming pregnant will want to be careful or consult their doctor about their diet, because too much cadmium can cause birth defects. In adults, cadmium can build up in the body, but high levels are most common in heavy smokers or people who live or work in areas with high levels of environmental cadmium. High levels in the blood could cause kidney disease and fragile bones. So if you work (or worked) at a job that exposes you to heavy metals, lived in a polluted city, or have a hobby that exposes you to heavy metals (like making stained-glass windows, which involves smelting), you may want to consider ways to keep your additional intake of cadmium as low as possible. You can take a test to see what your blood levels are, so consult your doctor.

Interestingly, vegetarians and vegans can be more at risk from cadmium because of their diet. But this doesn’t mean you should avoid these diets. They have many benefits, and non-vegetarian diets have their own issues. But vegetarians and vegans should make sure they get enough calcium and iron, which help limit the body’s absorption of cadmium. (Actually, everyone should make sure they get enough calcium and iron, but it can be more difficult with a vegetarian or vegan diet.)

Lead in chocolate, unlike cadmium, is mostly the result of how cocoa beans are cured. They are often dried in the sun on open ground or near roads, where they can be contaminated by dust and pollutants. Drying the pods in cleaner spots can lower the lead content considerably, and it may also be possible to remove lead at the processing plant, since the lead is mostly on the pod, not on the beans. Lead is particularly dangerous to children under six years old, slowing growth and damaging the brain and nervous system. Consequently, milk chocolate is probably best for children and in moderate amounts. For adults, elevated lead levels in the blood are again usually associated with jobs that expose them to heavy metals (now that we’ve removed lead from our gasoline and paint). High levels of lead can cause hypertension and decrease kidney function.

The Consumer Reports findings are eye opening, but as with any study, it’s important to look at things like method and criteria. For instance, Consumer Reports used California's acceptable-level standards for its study, which, according to Johns Hopkins Medicine toxicologist Andrew Stolbach, are intentionally "very conservative” in order to protect people at higher risk. He says that chocolate in moderate amounts is not something to worry about. (NPR article listed below.) This is not to downplay the health implications of the study, but to note that they should be taken in context. For instance, the European Union’s allowed level for cadmium in dark chocolate—set in 2019—is .80 mg/kg, about twice what California specifies. In the end, we each have to decide how much dark chocolate we are comfortable consuming, given our own health and exposure to heavy metals from other sources.

The health benefits of chocolate can be obtained from other food sources. Foods like apples, berries, grapes, and broad beans—or green tea, matcha, or red wine—supply substantial amounts of the same flavanols as cocoa. And you can get flavonols (not to be confused with flavanols!) in onions, kale, beans, etc.—and apples, tea, and berries. It bears repeating: The best diet is a varied one, with moderate amounts of many kinds of foods, with an emphasis on a variety of fresh vegetables. Some recommendations say we should aim for 30 different vegetables in a week! Other sources suggest five or six vegetables a day without requiring variety, but diversity supports a healthier gut biome. You don’t have to obsess over the details, just try to eat a varied, moderate diet.

Levels of Cadmium and Lead in Our Dark Chocolate Bars

The levels of cadmium and lead in chocolate bars vary tremendously. Below you can see if bars we carry tested above or below the amount California allows. Remember, California standards are very strict in order to protect those most vulnerable, such as children. The Consumer Reports results are based on one ounce of chocolate, which is about seven or eight little squares of an Equal Exchange bar. Since Consumer Reports tested a limited number of chocolate bars, we can only infer that a different bar from the same company with the same cacao content will be similar to the tested bar. Choosing a bar with 60% cacao over one with 70% or 80% should substantially lower exposure to cadmium and lead.