Raw vegan, vegan, and vegetarian diets may result in health benefits if they are "clean," that is, free of the processed foods that make up so much of the SAD.
Get rid of the frankenfoods, and yeah, you're likely to feel better than you did before. That does not mean that vegan/vegetarian diets are optimal.
I was "flegan" (mostly vegan, but flexible about occasional exceptions for practical reasons) for 3 years. Felt great until I started asking more of my body (bodybuilding) and the grains/legumes caught up with me (bloating). Went primal. Problems solved.