The problem with this assertion is that vegan diets don't pass the "common sense" test you are advising. Humans have been hunter-gatherers for most of history. Only recently did processed grains and refined sugar become part of the typical diet, and that is when heart disease , autoimmune disorders, obesity, and diabetes skyrocketed. The dietary guideline that "canola oil" (chemically extracted from the rapeseed using solvents) is healthier than animal saturated fat (that we have eaten since we appeared on this planet) doesn't even pass the common sense test a little bit.