The Paleo diet: were cavemen really so health-conscious?
The Paleo diet has won thousands of fans with its seemingly straightforward logic that what was good for our metabolism when we lived in caves is likely to be good for us today.
High in meat, fish and vegetables, it largely excludes dairy and cereal or anything else that emerged in the agricultural revolution, arguing that it was a protein-rich regime that fuelled massive brain growth for early humans.
But a study from University College London appears to cast doubt on that claim. It seems early man did not steer clear of carbohydrates at all. In fact, early communities must have been eating starchy plants in abundance for such rapid brain growth.
Professor Mark Thomas said carbohydrates should be "put back" into the Paleo diet because it is likely that they, alongside meat, allowed humans to become the most dominant species.
"The global increase in the incidence of obesity and diet-related metabolic diseases has intensified interest in ancestral or 'Palaeolithic' diets," said Prof Thomas. "Surprisingly, however, there is little clear agreement on what quantitatively constitutes a healthy diet, or indeed a Palaeolithic diet, with much conflicting information disseminated to the public. Eating food suited to the way our metabolisms evolved is a fantastic idea, but if you buy a book on the Paleo diet, it's probably rubbish. We know so little about what the Palaeolithic diet was."
The Paleo diet, which appeared in the 1960s and uses the American spelling, is based on the idea that, after the discovery of toolmaking, early humans were able to kill animals and move away from a fibrous, plant-based diet to begin eating more meat.
The change to a meat-rich diet was thought to be behind the evolutionary changes in brain size but Prof Thomas said it was a combination of the invention of cooking and the emergence of starch-digesting enzymes in the saliva and pancreas that allowed the rapid growth.
"Plant carbohydrates and meat were both necessary and complementary dietary components in human evolution," he said.