 There are two components of psychological health, the absence of mental health disorders, such as depression, as well as the existence of positive psychological well-being. That's the focus of an emerging field of positive psychology, focusing on happiness, life satisfaction, and flourishing, which may translate to physical benefits, such as improvements in blood pressure, immune function, and longevity. What is the contribution of food consumption to well-being? Well, studies have linked the consumption of fruits and vegetables with enhanced well-being. A systematic review of research found evidence that consuming fruits and vegetables was associated with increased psychological well-being. Oh, OK, but that's just an association. A famous criticism in this area of research is that maybe there's just some inherent personality trait, or a type of family upbringing, that might lead people simultaneously to eat in a healthy way, and also to have better mental well-being. So the diet is merely correlated with, but incorrectly gives the appearance of helping to cause, the level of well-being. But recent research circumvented this problem by seeing if changes in diet are correlated with changes in mental well-being, in effect studying the evolution of well-being and happiness after increases in the consumption of fruits and vegetables. And look at that graph, a straight line increase between how much more fruits and veggies people started eating and their change in life satisfaction over time. Increased fruit and vegetable consumption appeared predictive of increased happiness, life satisfaction and well-being, up to 0.24 life satisfaction points for an increase of eight portions a day. What does that mean? Is that a lot? Is that a little? That's a lot! Equal in size to the psychological gain of going from unemployed to getting a job. My daily dozen recommendations for at least nine servings of fruits and veggies a day. This study was done in Australia. It was repeated in the UK, and researchers there found the same thing, though the Brits may need to bump up their daily minimum to more like 10 or 11 servings a day. OK, but does eating fruits and veggies also reduce the risk of depression and anxiety? I mean, well-being is nice, and governments and medical authorities are often interested in the determinants of major mental illness, not life satisfaction, and indeed, using the same dataset, but instead looking for mental illness, eating fruits and vegetables may help to protect against future risk of clinical depression and anxiety as well. A systematic review and meta-analysis of dozens of studies found that every 100 gram increased intake of fruit was associated with a 3% reduced risk of depression. That's about half an apple. Yet, less than 10% of most Western populations even consume a bare minimum. Maybe the problem is we're just telling people about the long-term benefits of fruit intake for chronic disease prevention rather than the near-immediate improvements in well-being. So, maybe we should be advertising the happiness gains, but first, we need to make sure they're real. We've been talking about associations. Yes, a healthy diet may reduce the risk of future depression or anxiety, but being diagnosed with depression or anxiety today could also lead to lower fruit and vegetable intake. Now, in these studies, you can indeed show that the increase in fruit and vegetable consumption came first, and not the other way around, but as a great enlightenment philosopher pointed out, just because the cock crows before dawn doesn't mean the cock caused the sun to rise. To prove cause and effect, you need to put it to the test with an interventional study. Unfortunately, to date, many studies were like this, where those randomized to eat fruit showed significant improvements in anxiety and depression, fatigue and emotional distress. Wow, amazing! But that was compared to chocolate and potato chips. Apples, clementines, and bananas making people feel better than assorted potato chips and chunky chocolate wafers. Not exactly a revelation. This is the kind of study I've been waiting for, a randomized controlled trial in which young adults were randomized to a diet as usual group, encouragement to eat more fruits and veggies, or a third group given two servings of fruits and vegetables a day to eat over and above their regular diet. And the ones given fruits and veggies showed improvements in their psychological well-being, with increases in vitality, flourishing, and motivation within just two weeks. However, simply educating people to eat their fruits and vegetables may not be enough to reap the full reward. So perhaps greater emphasis needs to be placed on actually providing people with fresh produce, for example, offering free fruit for people when they shop. I know that would certainly make me happy.