Really? Is that true? What groups are you talking about?
> It's only when the 20th century rolled around, and meat became cheap/available everywhere, that people started eating meat once a day, leading to a spread of all kinds of diseases, heart attacks, cholesterol, cancer, etc.
Ok, interesting hypothesis. So assuming this is true, people in 1830 ate less meat and had less heart disease than people in 1930, right?
What if I told you, in the US, the opposite is true? That, on average, people ate more meat in 1830 and had less heart disease than people in 1930?
If people aren't eating meat, what are they eating? grains? sugars? How would you create a study to test your hypothesis than meat consumption causes heart disease? Has this been studied? What were the results?
If people aren't eating meat, what are they eating? grains? sugars? Vegetables, fruits, legumes, whole grains, nuts, etc. Most people in the US who eat tons of sugar are not vegetarians.
How do you know this? Have you studied the sugar consumption of vegetarians?
It's not that simple. The Inuit are an obvious counterexample. In fact, if you look at many hunter gatherer societies (Ache, Yanomamo, Waorani, !Kung, etc), almost all eat some form of meat (I'm including arthropods as meat) almost every day.
Cancer, heart disease and other afflictions that appear later in life are probably more common in the 20th century largely because life expectancy is so much longer than it used to be, not because of regular meat eating.
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.
It's only when the 20th century rolled around, and meat became cheap/available everywhere, that people started eating meat once a day, leading to a spread of all kinds of diseases, heart attacks, cholesterol, cancer, etc.