A report in Consumer Reports in 2022 said they found lead and cadmium in several brands of dark chocolate. These heavy metals can cause serious health problems. So how do lead and cadmium get into dark chocolate?
Toxicologist Michael J. DiBartolomeis, PhD, studied how these metals contaminate chocolate. The metals are found in cocoa solids, which are part of the cacao bean. The levels of cocoa solids in dark chocolate are higher than they are in milk chocolate, which is why dark chocolates have more problems with contamination.
The heavy metals get into the cacao bean in different ways. Cadmium is usually in the beans already when they are harvested because the plants take up cadmium in the soil, which accumulates in the beans.
But lead gets into the beans after they are harvested. Typically, the beans are left to dry in the sun for days, since they are wet and sticky after harvest. This drying period also ferments the beans, which develops the chocolate flavor. Dust and dirt that is filled with lead blows onto the beans as they dry. That dust comes from industrial sites and also where leaded gasoline is used in cars.
So, to lower cadmium levels, growers can take some steps. First, they need to look at the soil where the beans are grown, and use plants from regions with lower levels. Beans from regions with more cadmium can be blended with beans from regions with less of that heavy metal to reduce the contamination. In addition, cadmium levels increase as the tree ages, so replacing older trees with younger ones would help.
For the lead issue, growers and chocolate makers can minimize soil contact with drying beans by drying them on tables away from roads and with protective covers. They could also remove lead during the cleaning process.
