What we put in our bodies is about much more than just "eating." The New York Times reports:
Eating a Mediterranean-style diet — packed with fruits, vegetables, legumes, nuts, olive oil and fish — is good for your heart, many studies have found. Now scientists are suggesting the diet may be good for your mental health, too.
...Over time, those who had scored between 5 and 9 on the Mediterranean diet were 42 percent to 51 percent less likely to develop depression, the study found, than those who scored between 0 and 2. full article
As a vegan, I can tell you that the way that I eat has definitely changed more than my pantry. Aside from experiencing an increase in energy, conscious eating with an awareness of where my food comes from has added more mindfulness and happiness to my life. Yes, I will kiss a perfect tomato when I find one, take pride in the color combination of my chopped vegetables, make scrumptious wholesome foods for friends and fam, and smell my whole grains before I eat them. And since this transition, I am a more balanced, more peaceful and less stressed person.
I could get technical and list studies of how overhauling dietary lifestyles can modify misbehavior in children, but it's really late for me, so feel free to google that one.