Dark chocolate is definitely one of the more tooth-friendly options when it comes to sweets. It doesn’t stick to the teeth like gummies or caramel or nougat. It’s less acidic than hard candy and doesn’t remain in the mouth as long. It usually contains less sugar than milk chocolate.
Dark chocolate even contains some compounds that can support good oral health, such as theobromine. This bitter alkaloid supports natural tooth remineralization while lowering levels of S. mutans, one of the main pathogens involved in tooth decay. It’s also an anti-inflammatory antioxidant – one of several that are naturally found in cocoa.
But there’s a dark side to some brands of dark chocolate.
About a year and a half ago, Consumer Reports released test results showing that some dark chocolate products can contain high amounts of cadmium and lead. Organic brands were not exempt. In fact, some of the products found to be highest in these toxic metals were organic, non-GMO chocolate bars.
Now, most of us have an idea of why lead is a concern. There’s no safe level of exposure. Lead can severely affect the brain and nervous system. In children, even low levels can result in developmental issues such as lower IQ, learning difficulties, and behavioral problems. It can interfere with growth.
The less familiar cadmium is a carcinogen. It has toxic effects on the skeletal and respiratory systems, as well as the kidneys. It may cause reproductive issues. As with lead, even very low levels of exposure to cadmium can cause problems.
How do these metals get into chocolate? Cadmium is taken up from the soil into the cacao plant itself, while lead appears to get onto the beans after harvest. The longer the beans are left out to dry, the more lead dust they accumulate from the environment.
Consequently, chocolate with the highest percentage of cacao tends to have higher levels of these toxic metals.
The subject has come up again thanks to a new study in Frontiers in Nutrition that investigated the presence of both cadmium and lead in dark chocolate products, as well as arsenic.
Seventy-two American cocoa products were tested in four distinct groups between 2012 and 2022. Their metal levels were measured against the maximum allowable dose levels under California’s strict Prop 65, a law that requires businesses to warn consumers about significant exposures to chemicals known to cause cancer, birth defects, or other reproductive harm.
The research team found that 43% of tested products had lead levels above that limit. Thirty-five percent had excessive cadmium levels. None exceeded the limit for arsenic. (Yay!)
Notably, organic products were more likely to have higher levels of cadmium and lead.
Though most products had metal concentrations below the maximum, the research team suggested that while consuming a single serving of most products probably isn’t too risky, eating multiple servings or combining them with other sources of heavy metals could mean higher exposure.
What else can you do to minimize your exposure while still enjoying dark chocolate?
- Choose varieties with a lower percentage of cacao. Below 70% is recommended.
- Choose products that use West African cacao instead of Latin American. The latter has been found to have higher metal levels than the former.
- Check brand reports online, seeking out products that have reliably tested lower for lead and cadmium than others. The Consumer Reports piece mentioned above provides a good starting point.
- Eat a diverse, nutritionally dense diet, including lots of fresh produce and whole grains. These can help reduce the absorption of heavy metals due to their fiber and phytate content. (If you have concerns about eating grains, this episode of the Wise Traditions podcast offers some good guidance for including them in your diet.)
