This is a distorted view of history. Western societies in 1800 were among some of the sickliest and weakest that history has ever known, as population pressure was very high relative to available technology. Death in childbirth and childhood were both very common, and people from the Middle Ages enjoyed better health when using measures of average height. I've read speculation that the British Empire gained its edge because its people were able to get a small dietary advantage.

So we should not look at pre-industrial tradition for information on ideal nutrition. Those people were doing everything they could to survive, and they barely succeeded.