This is a question I’ve been asked thousands of times by patients and students. Most people have very little real knowledge of nutrition and, sadly, most nutritionists and nutritional “experts” are unconscious of the fact that much of their knowledge has been bought and paid for by food manufacturing corporations.
Few realize that the entire field we now think of as nutrition and the nutritionists it produces was started and funded by General Mills, specifically to sell processed foods made largely from grains.
That doesn’t mean there aren’t great nutritionists out there, but you’ll find that the great ones had to unlearn much of what they were taught, and relearn the truth through clinical trials and life experiences of their own.
I addressed this important issue recently in a response (below) to Rahul Dey’s question recently posted on my YouTube channel.