“Thousands of papers have been published on the important topic of what determines people’s subjective well-being and psychological health,” but what about the potential influence of the different kinds of foods people eat? I explore this in my video Which Foods Increase Happiness?.

“The rising prevalence of mental ill health is causing considerable societal burden. Inexpensive and effective strategies are therefore required to improve the psychological well-being of the population….A growing body of literature suggests that dietary intake may have the potential to influence psychological well-being.” Dietary intake of what? Well, given the strong evidence base for the health benefits of fruits and vegetables, researchers started there.

Cross-sectional studies from all over the world support this relationship between happiness and intake of fruits and vegetables. Those eating fruits and vegetables each day have “a higher likelihood…of being classified as ‘very happy,’” suggesting “a strong and positive correlation between fruit and vegetable consumption and happiness” and perhaps feelings of optimism, too.

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 didn’t just act as a marker for other healthy behaviors.

But how could eating plants improve happiness on their own? Well, many fruits and veggies contain higher levels of vitamin C, which is “an important co-factor in the production of dopamine,” the zest-for-life neurotransmitter. And, the antioxidants in fruits and vegetables reduce inflammation, which may lead “to higher levels of eudaemonic well-being.”

Eudaemonic? What’s that? “Aristotle’s notion of eudaemonia…described the highest of all human goods as the realization of one’s true potential,” which was the aim of a study: Researchers wanted to know whether eating fruits and vegetables was “associated with other markers of well-being beyond happiness and life satisfaction.” So, they tested whether consuming fruits and veggies was associated with “greater eudaemonic well-being—a state of flourishing characterized by feelings of engagement, meaning, and purpose in life.”

The researchers followed a sample of about 400 young adults for 13 days, and, indeed, the young adults who ate more fruits and veggies “reported higher average eudaemonic well-being, more intense feelings of curiosity, and greater creativity.” This could be followed on a day-by-day basis: greater well-being on the days they ate healthier. “These findings suggest that [fruit and vegetable] intake is related to other aspects of human flourishing, beyond just feeling happy.”

Not so fast, though. Instead of eating good food leading to a good mood, maybe the good mood led to eating good food. Experimentally, if you put people in a good mood, they rate healthy foods, like apples, higher than indulgent foods, like candy bars. Given a choice between M&M’s and grapes, individuals in a positive mood were more likely to choose the grapes. The results of these studies “lend support to a growing body of research that suggests that positive mood facilitates resistance to temptation.” Who needs comfort foods when you’re already comforted? It’s like which came first, the stricken or the egg? Yes, eating eggs may increase our likelihood of chronic disease, but maybe chronic disease also increases our likelihood of eating unhealthy foods. Which came first, the mood or the food?

If only there were a study that, instead of looking at well-being and diet on the same day, looked to see if there’s a correlation between what you eat today and how you feel tomorrow.

There is. In the study, researchers found the same “strong relationships between daily positive [mood] and fruit and vegetable consumption.” Additionally, “[l]agged 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 they normally do…[and] also felt more positive the next day.” So, eating fruits and vegetables really “may promote emotional well-being.” Single bouts of exercise can elevate one’s mood, so why not the same with healthy food?

How many fruits and vegetables? Seems we “need to consume approximately 7.2 daily servings of fruit or 8.2 servings of vegetables to notice a meaningful change” in mood.

For more on this topic, I invite you to watch Plant-Based Diets for Improved Mood & Productivity.

I mentioned in passing the benefits of exercise for boosting mood, and here is more on maximizing movement:

Sadly, there are 20 times more studies published on health and depression than there are on health and happiness. There is growing interest in the so-called positive psychology movement, though. See my video Are Happier People Actually Healthier? for more.

For all our videos on the latest research on vegetables, visit our Vegetables topic page.

In health,

Michael Greger, M.D.