I just read an article on the site of Dr. Greger, Nutritionfacts.
He tells us about studies that suggest a relationship between happiness and vegegable and frui intake.
"Those eating fruits and vegetables each day have a higher likelihood of being classified as “very happy". (...)
The largest such study was done in Great Britain, where a dose–response relationship was found between daily servings of fruits and vegetables and both life satisfaction and happiness, meaning more fruits and veggies meant more happiness. People who got up to seven or eight servings a day reported the highest life satisfaction and happiness. And these associations remained significant even after controlling for factors such as income, illness, exercise, smoking, and body weight, suggesting fruit and vegetable consumption wasn’t just acting as a marker for other healthy behaviors."
The explanation, says Dr. Greger, can be found in the high levels of vitamin C, which help to promote the production of dopamine, a neurotransmitter that improves our 'zest for life'.
Also the antioxidants in fruits and veggies reduce inflammation, which may lead to higher levels of eudaemonic well-being, said Greger.
But maybe the good mood led to eating good food instead of the other way around?
"Experimentally, if you put people in a good mood, they rate healthy foods, like apples, higher than indulgent foods, like candy bars. (...). The results of these studies lend support to a growing body of research that suggests that positive mood facilitates resistance to temptation."
"Lagged analyses showed that fruit and vegetable consumption predicted improvements in positive mood the next day, not vice versa. On days when people ate more fruits and vegetables, they reported feeling calmer, happier, and more energetic than normal, and they also felt more positive the next day. So, eating fruit and vegetables really may promote emotional well-being."