Lead among other heavy metals found in many dark chocolate bars: Research

Researchers have found that in the United States, several dark chocolate products are contaminated with lead and cadmium, two highly toxic metals. The study was led by scientists at George Washington University and published Wednesday (Jul 31) in the peer-reviewed Frontiers in Nutrition. 

Researchers have analysed over 70 dark chocolate products from retailers such as Whole Foods Market, Amazon and GNC. They tested the products in order to check whether or not heavy metals lead, cadmium or arsenic were present in them. None were tested above the maximum contamination level. 

The study was carried out using samples over a period of eight years from 2014 to 2022. Notably, the researchers have not disclosed product names. 

The study discovered that 43 per cent of the goods tested had levels of lead contamination that were above permitted standards, and 35 per cent had levels of cadmium contamination as per California law's permissible limits for heavy metals in food. 

"The amount of lead that was found, in general, was not alarming. But most people probably don't have a great handle on what their heavy metal exposure is," Leigh Frame, the co-lead author of the study and the executive director of the office of integrative medicine and health at George Washington University. 

Frame noted that food researchers often use the 1986 regulations as a safety standard because the US Food and Drug Administration (FDA) doesn't set limits on heavy metals in most foods. Notably, the FDA does have suggested limits for chocolate and sugar-based candy but only for children. 

The threshold for heavy metals in foods is 0.5 micrograms a day as per California guidelines. Researchers have found that the levels of lead and cadmium in chocolate samples varied from 0.29 to 14.12 microgrammes per daily serving, with 4.1 microgrammes per day being the maximum permitted. 

The study revealed that lead levels in the samples ranged from none to as high as 3.316 microgrammes per daily serving, with 0.5 microgrammes per day as the maximum allowed per California guidelines. 

The researchers also discovered that the levels of contamination in organic items were higher, but they were unable to ascertain how the metal contaminations entered the chocolate products. 

Frame said, "You actually cannot avoid exposure to heavy metals in the diet. It's really not about avoiding them; it's about making sure you're not getting too much."