All recognize that different diets can have different health affects. The Western diet is held to be particularly deleterious. The Japanese are said to live longer due to diets high in fish and seaweed. The Mediterranean diet apparently lowers cardiovascular risks. The Irish during the 19th century lived largely on potatoes and had high rates of schizophrenia which have normalized now.
Diets could also affect culture. A hunting and gathering diet was high in saturated fats. The switch over to agricultural ways of putting food on the table had to reduce animal protein intakes for the great majority of individuals though elites would have had access to meat. The differences between hunting and gathering cultures and agricultural cultures could be due at least in part to differences in diets. The characters of individuals in the 19th century was much different than the characters of individuals today. A lot of beef and saturated fats were eaten in the 19th century compared to today. Sodas were basically unknown in the 19th century. Coffee appears with the modern era in the West. With the arrival of the modern era there were huge changes in human character where some of those changes could be due to drinking coffee. Individuals received more sunlight in the past. Mediterranean areas where individuals are ebullient receive a lot more sunlight than Scandinavia where individuals are dour. There has been a massive switch into supplements which could be adversely affecting the mood of the nation. With different diets the World is seen in different ways.
A lot of historical changes are apparently inexplicable. Diet could play a key role in how history unfolds.