If you read widely in terms of nutrition, you see every claim made by a particular group will have counter claims made by opposing groups — each group having a set bias in terms of advocating a specific diet. So it is much like a war of competing claims. Therefore, there is little doubt that as a science, nutrition is perhaps the most controversial area of study, given this background of competing vested interests.
But there is little to doubt on one point that has been proven over and over again with statistically sound evidence from large-scale experiments — that the vegan, plant-based diet is the healthiest relative to longevity and overall health, and this by a large margin when compared to any other sort of diet.
So if you want to live a long life and in good health, the choice to do so — to the extent you can influence it — is absolutely clear.
Sadly, relatively few people make that choice because they don’t want to give up the foods they have come to enjoy — despite the consequences. The vast majority of people make a compromise with the devil sacrificing their health for pleasure.