Should I Worry About Heavy Metals in Chocolate?

Should I Worry About Heavy Metals in Chocolate?

Recently there has been a lot of buzz around toxic heavy metals like cadmium and lead in dark chocolate.  Wondering if you need to give up your favorite Hershey, Ghirardelli, Lindt, Dove, or Nestle sweet chocolate treats in place of safer choices due to these levels of heavy metals or is it OK to indulge?  Let’s see what the science has to say!

The quick answer is no, you don’t have to worry about eating your dark chocolate.  While it’s true that chocolate contains some of the highest levels of cadmium and lead in our food supply it’s important to remember that the “dose makes the poison.” That is, you’d have to eat a lot of chocolate on a daily basis in order to worry about these heavy metals. But, I’m getting ahead of myself. To help make sense of the science, it’s important to understand what is meant by Acceptable Daily Intake or ADI, which is covered in the following video.  

While our bodies and our gut microbiomes have extensive detoxification pathways allowing us to detoxify heavy metals, there can be a threshold of intake of certain food compounds or additives above our body’s ability to detoxify. Above that threshold of intake, these compounds can cause issues either via acute or chronic exposure. However, below that threshold, they aren’t harmful. Looking at chocolate, it’s not that heavy metals are harmless, but instead that dose matters. Many food toxin myths disregard the impact of dose. The adage “the dose makes the poison” underlies the field of toxicology, i.e., the study of how chemicals adversely impact health—everything is a poison in a large enough quantity (even water!).

Most food additives and pollutants have Acceptable Daily Intake (ADI) levels established, or alternatively a chronic reference dose or tolerable daily intake, both of which are an estimate of the amount of a substance in food or drinking water that can be consumed daily over a lifetime without presenting an appreciable risk to health.

The ADI is typically 100 to 1000 times lower than the threshold known to cause harm (called the No Observable Adverse Effect Level [NOAEL], and this is an important part of the conversation when it comes to busting food-phobic myths. Just because something is harmful and causes health problems in large quantities, that does not mean it is harmful in any quantity—we must compare to the lower levels we typically consume.

Now that we understand a bit about toxicology and maximum allowable dose levels, let’s do some math and look at how much chocolate we can safely consume every day to stay below or at the ADI for cadmium and lead.

A comprehensive 2018 study measured the amounts of heavy metals, lead and cadmium, in 144 samples of cocoa powder, dark chocolate, milk chocolate, and cocoa nibs purchased at retails stores in Maryland.

Before moving on, let’s take a step back and clarify a few things as the nomenclature around cocoa and cacao can be a bit confusing.  The word “cacao” and “cocoa” may look similar and are sometimes used interchangeably, though incorrectly.  “Cacao” actually refers to raw, unprocessed cocoa beans, which come from the Theobroma cacao tree, while “cocoa” refers to beans that have been roasted, and chocolate is a mixture of both cocoa solids and cocoa butter.

In the 2018 study both lead and cadmium levels correlated with the amount of cocoa solids, which means higher levels were found in cocoa powder, followed by cocoa nibs, dark chocolate and then milk chocolate.

The chronic reference dose for cadmium is 1 μg/kg/day (where μg refers to micrograms and is also sometimes represented as mcg).

The mean cadmium level detected in dark chocolate was 0.27 mg/kg of chocolate, meaning a 70-kilogram adult would need to consume 9 ounces (250 grams) of dark chocolate every single day (3 large dark chocolate bars) to hit the chronic reference dose for cadmium.

Considering the test results showing the highest level of cadmium detected in the study, you’d still need to eat over 2 ounces (57 grams) every single day to hit the chronic reference dose for cadmium.

Now, let’s take a look at lead. The chronic reference dose for lead is 0.26 μg/kg/day for young children and 0.16 μg/kg/day for older children and adults.

The mean lead level detected in dark chocolate was 0.03 mg/kg of chocolate, meaning a 70-kilogram adult would need to consume over 13 ounces (370 grams) of dark chocolate every single day (4+ large dark chocolate bars) to hit the chronic reference dose for lead.

Considering the highest level of lead detected in the study, you’d still need to eat 3.5 ounces (100 grams) daily to hit the chronic reference dose for lead.

Conversely, the health benefits of chocolate consumption are numerous and include lower blood pressure, protecting against cardiovascular mortality, and death from all causes, aspirin-like effects on platelets, antidiabetic effects, reducing parameters of stress, supporting maintenance of a healthy body weight, improving cognitive performance, reducing stroke risk (it acutely improves cerebral blood flow), and it may even have anticancer properties. These benefits are linked to the large concentrations of phytonutrients with antioxidant activity found in chocolate and cap out at about 1 ounce per day (you could say that’s the sweet spot), which is far below the level of concern for heavy metal contamination based on the study outlined above. The situations where you might need to worry is if you had high levels of cadmium or lead exposure from other sources or if you are eating 9 ounces or more of chocolate per day!

Bottom line, most of us don’t need to be concerned about heavy metals in chocolate.  So go ahead chocolate lovers and indulge in your favorite chocolate products, be it milk chocolate, dark chocolate, chocolate chips, cacao powder, brownie mixes, cocoa beans, cake mix, or hot chocolate aka hot cocoa! Enjoy!