Optimizing nutrition is a very important part of improving mental and physical health. Nutrition affects every system in the body and every cell in the body. It is a relatively accessible and identifiable factor underlying illness.
As a single factor, poor nutrition can increase the occurence of heart disease, diabetes, and obesity by 600%. That is a huge increase.
Once I saw Weston Price’s and more recent data about high nutrient density vs. low nutrient density diets and the health consequences (e.g. look at Weston Price’s photos), it completely clarified what I had to do to improve the health of my patients.