The 'caveman' or paleo diet promises a better health, where you avoid processed food and only eat meat, fish and seeds. This is what our ancestors did. But a new study suggests some of the food they ate might not only be unhealthy but severely toxic.
Archaeologist Hans Peter Blankholm of the Arctic University of Norway and his colleagues focused on Stone Age humans living on the shores of the Norwegian Arctic, in an area known as Varanger to find out what kind of toxic food our ancestors consumed.
The researchers identified eight archaeological sites from 6300 to 3800 years ago. No human remains were studied; instead, they analysed the bones of dozens of Atlantic cod and harp seals found in ancient garbage pits. Many slash marks on the seal bones indicate that the species have been butchered rather than just skinned.
According to previous geological research, these animals were among the main ingredients in the diet of the people who lived here. It is also known that the hunter-gatherers had eaten haddock, whale, dolphin, reindeer and
The cod bones at these sites contained more than 20 times the maximum level of cadmium and up to four times the highest level of lead deemed safe in meat by the European Food Safety Authority, the team reports in Quaternary International. Cadmium can cause disease of the heart, liver and lung, while lead can damage the brain and nervous system.
Seal bones at the sites contained up to 15 times the permitted cadmium levels, and up to four times the average lead levels. The amount of mercury–which in humans may trigger liver, kidney, and immune system harm–was also high in both species.
Blankholm considers such heavy metal amounts of seafood "unhealthy, if not dangerous," but he admits it's unknown how much the primitive people's diet would have affected them. The heavy metal impact could have been blunted by replacing the seal and cod with fruit or meat from reindeer and rabbits. The inhabitants of Varanger may also have not lived long enough to feel the full impact of the accumulating pollutants.
"This study raises interesting ideas," says Katheryn Twiss, an archeologist at Stony Brook University, who says scientists used only 40 bones to draw conclusions on levels of pollution around different sites and some 2500 years ago which does not fully represent Norwegian diets from thousands of years ago.
Even if heavy metals polluted cod and seal, Twiss notes, these meat will certainly have been a good source of protein and other key nutrients, too. So maybe after all, the paleo diet wasn't all bad.