Your surgeon brother thinks diet doesn't affect healthy? Ugh.
My friend's father is a doctor (internal medicine) and my friend used to drink "ensure" for breakfast since his dad told him it was on of the healthiest things to eat.
And even when some people are cured because of a big switch in diet (like super-high blood pressure or cholesterol normalizes on a high-raw vegan diet), the doctor isn't even interested in how they did it.