The “primitive diet” may be toxic.

If you eat like your ancestors, you will be healthier. At least that’s the promise of some modern rhetoric, such as the “caveman” or the Stone Age diet, which is characterized by avoiding processed foods and grains and eating only things like meat, fish and seeds. But a new study suggests that food eaten by early humans in Norway may not only be unhealthy, but also toxic.

In some cases, these people may consume more than 20 times the level of hazardous metals recommended by today’s humans. Pollutants have been entering the human food chain for thousands of years.

To find out if the problem is more common, archaeologists at the Norwegian University of the Arctic studied Stone Age humans living on the Norwegian Arctic coast in a region called Varanger.

The researchers selected eight archaeological sites from the area, spanning 6,300 to 3,800 years ago. Instead of studying any human remains; they analyzed the bones of dozens of Atlantic cod and Greenland seals found in ancient dumps. Most of the cutting marks on the seal’s bones suggest that the animals were slaughtered to get their meat, not simply peel it.

The cadmium content in the cod bones at these sites is more than 20 times the highest safe content in meat, and lead is four times the highest, the study said. Cadmium can cause kidney, liver and lung disease, while lead can damage the brain and nervous system.