A study from Australia in 2016 found improvements in psychological well-being after increased consumption of fruit and vegetables. We wanted to know if this result was correct using a larger selection (more than 40,000 participants) from the UK household survey.
Our analysis showed that the increase in fruit and vegetable consumption is linked to increases in self-reported mental well-being and life satisfaction in data over a five-year period, even after reporting other determinants of mental well-being such as physical health, income, and health. consumption of other foods.
The benefits of physical activity for mental health are well established. The estimates from our work suggest that adding one serving to your diet per day may be as beneficial for mental well-being as walking an extra seven to eight days a month. One portion equals one cup of raw vegetables (the size of a fist), one half a cup of cooked vegetables or chopped fruit, or one piece of whole fruit. This result is encouraging as it means that a possible way to improve your mental health can be as simple as eating an extra piece of fruit each day or having a salad with a meal.
It is important to emphasize that our results alone cannot reveal a causal link between fruit and vegetable consumption for increased mental well-being. And we cannot rule out so-called "substitution effects". People can only eat so much in one day, so whoever eats more fruits and vegetables can only have less space in the diet of unhealthy foods. Although we presented bread and dairy products in our study, future research should track all other foods consumed to exclude alternative explanations.
But when taken in combination with other studies in this area, the evidence is encouraging. For example, a randomized study conducted in New Zealand found that various measures of mental well-being, such as motivation and vitality, were improved in a treatment group where young adults were asked to eat two additional servings of fruit and vegetables a day for two weeks
Although our own study cannot rule out that people with a higher mental health level can eat more fruit and vegetables as a result . A new comment on our work by the authors of the 2016 Australian study highlights this. The authors show that the number of fruits and vegetables consumed in one day can predict if someone is diagnosed with depression or anxiety two years later. But the reverse does not seem to be true. Being diagnosed with depression does not seem to be a strong prediction for the consumption of fruit and vegetables two years later. This suggests that eating fruits and vegetables may be more likely to affect mood and not the other way around.
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Looking for Causes
 Although several studies, including our own, have found a link between the consumption of fruits and vegetables and mental well-being, we need Great efforts to provide strong evidence that the link is causal. But randomized controlled trials are expensive, so another way to identify causal relationships is to focus on the biological mechanisms that link the chemicals commonly found in fruits and vegetables to physical changes in the body. For example, vitamins C and E have been shown to lower inflammatory markers linked to depressive mood.
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Although more research is needed, our work adds to growing evidence that eating fruits and vegetables and having higher levels of mental well-being are positively related and the signs of a causal relationship from other recent studies are encouraging. We do not suggest eating fruits and vegetables is a substitute for medical treatment, but an easy way to improve your mental health may be to add a little more fruit and vegetables to your daily diet.
Neel Ocean is a research employee in behavioral economics and Peter Howley is an associate professor in economics at the University of Leeds. They receive funding from Global Food Security's "Resilience of the UK Food System Program" with support from BBSRC, ESRC, NERC and Scottish Government.