What To Know About Dark Chocolate and Heavy Metals

A recent Consumer Reports investigation struck fear into the hearts of chocolate lovers everywhere. After testing 28 dark chocolate bars, scientists detected the heavy metals lead and cadmium in all of them. For 23 of the chocolate bars, eating just an ounce would put an adult above the daily upper threshold recommended for heavy metals in food by public-health officials in California, which the authors said they chose because it is the most protective standard available.

Experts say, however, that this report offers just one small window into a larger problem. Heavy metals are detectable in many different foods, and limited testing and a lack of labeling requirements leave consumers in the dark. But there are steps you can take to limit your exposure and protect your family.

What are the risks of eating foods containing heavy metals?

Some metals, like iron, are essential for your health. Others, like lead and cadmium, serve no useful purpose for the body in any amount and are toxic in large quantities, according to the U.S. Centers for Disease Control and Prevention (CDC).

No level of lead, for instance, is considered safe, but it becomes more dangerous as it accumulates in the body. The gravest risks are for children, since their bodies are small and still developing. According to the CDC, lead exposure can affect nearly all organ systems, but is particularly dangerous for the central nervous system, which includes the brain. A blood concentration as low as 10 µg/L can slow children’s neural development. In both children and adults, lead can also affect memory and cause conditions like anemia, stomach issues, and high blood pressure.

Exposure to cadmium over a long period, meanwhile, can lead to stomach problems and may damage kidneys, in both children and adults.

The recent finding that lead makes its way into popular chocolate bars didn’t surprise Dr. Robert Wright, a professor of environmental medicine at the Icahn School of Medicine at Mount Sinai. Some contamination is inevitable. Since dark chocolate is not a staple food and therefore, you (and especially children) are probably not eating it that much to being with, Wright says he wouldn’t discourage enjoying it in moderation (although he suggests that parents not feed their kids the brands that Consumer Reports says have the most lead and cadmium). Wright adds that he hopes that dark chocolate’s time in the headlines will lead companies to take a closer look at why some bars have more heavy metals than others.

Why are there heavy metals in food?

Many heavy metals, including lead and cadmium, appear naturally in soil, and they make their way into the food supply from the ground. But some have been added to the environment by human activity globally, including pollution caused by farming, industry, and transportation.

For instance, lead was used in gasoline in the U.S. for decades until it was banned in 1996, and it spread through the atmosphere and settled on the ground, where it remains in the soil to this day, says Wright. “There are measurable amounts [of heavy metals] in pretty much all foods,” he says, “simply because there are metals in our soil.”

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The FDA has cautioned the public about the potential for unsafe amounts of heavy metals in other foods, including mercury in fish and arsenic in rice. Mercury is commonly found in fish due in part to runoff from natural causes, like volcanic eruptions, and as a waste product of certain human activities, like burning coal for fuel, burning municipal waste, and as runoff from industrial processes like electrical equipment manufacturing. Rice, meanwhile, tends to absorb arsenic from the soil and water in which it grows. Arsenic also occurs naturally, as part of the earth’s crust, and as a result of human activities, like pesticide use.

So, should I stop eating dark chocolate?

There are two main reasons not to fixate on chocolate, says Katarzyna Kordas, an associate professor of public health at the University at Buffalo. First, the reality is that heavy metals are probably present in trace amounts in many different foods. While the FDA tests a limited number of foods each year, including a few hundred annually for the Total Diet Study, it does not test food from specific brands or stores, and manufacturers are not required to disclose heavy metals on food labels.

“There have been calls for better labeling and more transparency about what is in manufactured products. To do this, companies would need to test their products regularly and both make this information available and act on it to reduce heavy metals to the extent possible,” says Kordas. “It should not just be up to individuals to figure this out.”

But in the meanwhile, it doesn’t really make sense to harp on one food type. And that leads to Kordas’ second reason for not giving up on dark chocolate: if you do, you may miss out on the health benefits that have been connected to moderate consumption on the stuff. For example, studies show that the flavonols in dark chocolate can promote heart health.

How can I protect myself and my family from heavy metals in food?

It’s key to note that heavy metals can accrue in the body not just from food, but also from exposure to contaminated water, the air, and household and consumer products, says Wright. In other words, no matter what you do about your diet, it’s unlikely you will completely avoid them. But, you can definitely take steps to reduce your risk of dangerous levels of exposure.

Kordas says that instead of trying to avoid certain foods, for most people, it’s best to aim for a diet that contains a wide variety of foods, and to avoid eating a ton of any one food, Doing so “would lower our chances of sort of consuming too much of any one metal.”

A healthy, balanced diet is also thought to offer protection from heavy metals. If your body is deficient in heavy metals that are healthy in low amounts—like zinc and copper—it may absorb too many dangerous heavy metals like lead and cadmium, says Wright. And the CDC recommends that children eat diets rich in calcium, iron, and vitamin C, all of which can keep the body from absorbing lead. Overall, a healthy diet also makes bodies stronger, says Wright, and will promote the development of your child’s brain, which will help to counteract the effects of negative factors in their environment.

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