I don't know, how much it is true but mentioned here:
The Natural Human Diet
Human Evolution and the Rise of Meat-Heavy Diets
If it’s so unhealthy and unnatural for humans to eat meat, why did our ancestors sometimes turn to flesh for sustenance? During most of our evolutionary history, we were largely vegetarian: Plant foods, such as yams, made up the bulk of our ancestors’ diet. The more frequent addition of modest amounts of meat to the early human diet came with the discovery of fire, which allowed us to lower the risk of being sickened or killed by parasites in meat. This practice didn’t turn our ancestors into carnivores but rather allowed early humans to survive during periods in which plant foods were unavailable.
Modern Humans
Until recently, only the wealthiest people could afford to feed, raise, and slaughter animals for meat, and less wealthy and poor people ate mostly plant foods. Consequently, prior to the 20th century, only the rich were plagued routinely with diseases such as heart disease and obesity. Since 1950, the per capita consumption of meat has almost doubled. Now that animal flesh has become relatively cheap and is easily available (thanks to the cruel, cost-cutting practices of factory farming), deadly ailments such as heart disease, strokes, cancer, and obesity have spread to people across the socio-economic spectrum. And as the Western lifestyle spills over into less developed areas in Asia and Africa, people there, too, have begun to suffer and die from diseases associated with meat-based diets.
https://www.peta.org/living/food/natural-human-diet/