An epidemiological survey from decades ago, probably worse than useless. Spend a few months studying the hard sciences of archeological anthropology, evolution, biochemistry, digestive system, and the dietary guideline history, and it becomes incredibly obvious that humans evolved as apex carnivores. Cooking meat allowed us to jump directly to the top of the food chain. We have among the most acidic stomachs on the planet, next to vultures and hyenas. We were Hunters & Scavengers not Hunters & Gatherers.

Of course we preserved the pathways to use carbs in case of famine, but modern plants are covered in pesticides, shipped from across the world with no care for season or locality. Chronically elevated blood sugar damages the body. Glycation due to excess carbohydrates damages the body. There is no such thing as an essential carb, only essential fats and essential protein. All of our organs are made of fat and protein, for like 1 to 2% carbohydrates (glycogen), and the liver can create every last carb needed from gluconeogenesis. We simply don't have the hardware that the herbivores do to break this stuff down. Fiber is indigestible plant sugar, aka literal waste!

Besides the fact that plants and animals are made from different things, and not all protein is created equal. Ruminant animal fat has everything needed in the right shapes and proportions for high bioavailability. Plant based vitamin A and omega-3 for example can round to a near zero conversion rate in some people.

It's crazy, I know. But anyone who really claims to love science will be excited to look into this deeply and skeptically