The cocoa and chocolate you eat may be contaminated with the toxic heavy metal cadmium. Many people are consuming cocoa products for better health because ­cocoa and dark chocolate are sources of flavanols—200 mg/day of flavanols have cardiovascular benefits…while 500 mg/day may help improve memory.

The problem with cocoa as a flavanol source is that nearly all types are contaminated with cadmium, a toxin that with chronic exposure can damage kidneys. The World Health Organization says that cadmium levels in foods such as cocoa should not exceed 0.3 micrograms (mcg) per gram. Almost all popular cocoa powders that ConsumerLab tested in 2017 exceed that limit. Example: ­Bulletproof Chocolate Powder was found to contain 2.2 mcg per gram.

Cadmium occurs naturally in soil, especially in the sort of volcanic soil where cacao trees grow. This means that even organic cocoa contains it. There is cadmium in chocolate, too, although at lower levels than in cocoa powder because chocolate bars contain other ingredients. Still, some chocolate is high in cadmium. Example: Trader Joe’s Dark Chocolate Lover’s Bar 85% Cacao had 12 times as much cadmium as another brand, Endangered Species Chocolate with 88% Cocoa. A bar of Trader Joe’s contained 29 mcg of cadmium—seven times the daily limit in Canada for adults. (There is no US limit.)

If you like to drink cocoa, having a cup (using one tablespoon of cocoa powder) now and then is unlikely to expose you to too much cadmium. But be especially cautious about drinking cocoa if you have kidney disease.

Another option for getting a large amount of cocoa flavanols without contamination is the supplement CocoaVia, which is made from a concentrated cocoa extract. ­