It’s very difficult to test diets on humans. Best study to date is the China Study. It looked at Chinese villages that had different diets and shows that eating meat and dairy is correlated to lower life expectancy and more diseases.

https://www.quora.com/What-are-the-results-of-the-China-Stud...

The China Study is garbage and mostly detected hidden variables. People eating more meat were often living near (polluted) cities, smoking more, etc.

While I don’t agree the study is garbage their are limitations and imperfections to every study. Another great example was cancer rates in Norway from 1929-1948. In 1939, Norway lost almost all meat to the Nazi’s and you can see cancer rates drop immediately and significantly. In 1945 after the war ends cancer rates quickly rise again.

Check out the documentary forks instead of knives to see more examples like this.

Norway, along with most other countries during wartime, had severe food rationing going on. It's not a surprise that cancer rates dropped if people were malnourished and dying younger of... everything else but cancer and cardiocirculatory diseases.

The China Study is famously biased and scientifically dodgy [0, 1].

It was great for opening the topic and provoking discussion though, which is much needed.

[0] https://sciencebasedmedicine.org/the-china-study-revisited/

[1] https://chriskresser.com/rest-in-peace-china-study/

While I don’t agree the study is garbage their are limitations and imperfections to every study. Another great example was cancer rates in Norway from 1929-1948. In 1939, Norway lost almost all meat to the Nazi’s and you can see cancer rates drop immediately and significantly. In 1945 after the war ends cancer rates quickly rise again.

Check out the documentary forks instead of knives to see more examples like this.