The real ‘paleo diet’ may have been full of toxic metals

You’ll be healthier if you ate as your ancestors did. At least that’s the promise of some modern fads such as the “caveman” or paleo diet—characterized by avoiding processed food and grains and only eating things like meat, fish, and seeds. But a new study suggests the food some early humans in Norway ate may have not only been unhealthy, but downright toxic. In some cases, these people may have consumed more than 20 times the levels of dangerous metals recommended for humans today.

“This study raises interesting ideas,” says Katheryn Twiss, an archaeologist at Stony Brook University who was not involved in the work. But, she notes, the findings are limited to a small number of animal remains from just a few sites, and therefore may not fully represent the diets of Norwegians from thousands of years ago.

Pollutants have been entering our food chain for millennia. In 2015, for example, researchers reported that cod caught off the North American coast around 6500 years ago by Stone Age hunter-gatherers contained high levels of mercury. This metal occurs naturally in Earth’s crust and is thought to have leached into the oceans in greater concentrations after sea level rise covered more land. Once in the water, fish absorb mercury through their gills and their food.