It may not seem intuitively sound, but there’s plenty of solid evidence showing a strong link between increased consumption of plants (fruit and veg – FV) and an increase in measurable levels of happiness. We’ll take a quick look at some of the evidence and you’ll possibly be surprised by how convincing it is.
Where’s the evidence?
A 2013 review 1 found that previous research had indeed shown indications of a role for FV in promoting psychological well-being. They state in their study objectives that “A growing body of literature suggests that dietary intake may have the potential to influence psychological well-being. For example, studies have suggested that particular dietary constituents, including vitamins and minerals, might be beneficial to psychological health. However, in order to better reflect normal dietary intake, health-based research has increasingly begun to focus on whole foods and dietary patterns, rather than individual nutrients. One food group that has received increasing attention with regard to psychological health is FV. This is probably a result of the strong evidence base, which exists in relation to their protective association with a number of chronic diseases, as well as the fact that they are a rich source of some of the nutrients which have been linked to psychological health.”
However they concluded that: “…evidence to date can be summarised as largely inconclusive. The conflicting results may be partly due to methodological limitations and study design variations as highlighted throughout this review. A number of key inconsistencies were identified including sample sizes, populations examined, choice of outcome and exposure assessment tools, factors chosen as potential confounders and design issues with regard to experimental studies. These factors should be taken into consideration to improve the credibility of future evidence.”
So far, okay – but we haven’t yet shown a clear causal relationship between FV and happiness.
A 2012 UK study 2 (the largest study to date on this subject) gave evidence that eating more FV increases your general physical health; but what about the effect of eating FV on levels of happiness (Aristotle’s eudaimonia 3 – a state of ‘flourishing’ characterised by feelings of engagement, meaning, and purpose in life) ?
A 2014 Korean study 4 found that other factors, such as social/financial status, perceived stress levels, smoking, drinking, exercise, account, in part, for the relationship between positive psychological states and good health. In addition, they recognised that a ‘healthy diet’ is also important.
What constitutes a ‘healthy diet’?
The researchers concluded: “Our findings provide support for the relationship between happiness and fruit and vegetable intake. Participants who consumed a diverse, well-balanced diet that included sufficient quantities of fruits and vegetables were happier than those who did not.”
This positive conclusion about a relationship betwen FV and happiness had already been drawn in a previous 2011 Chilean study 5 , which concluded that people having “…fruits and vegetables each day had a higher likelihood of being classified as ‘very happy‘.”
This was then backed up by a 2013 Iranian study 6 which concluded: “Consistent with previous reports (Blades, 2009; Piqueras, Kuhne, Vera-Villarroel, Van Straten, & Cuijpers, 2011), this study suggests a strong and positive correlation between fruit and vegetable consumption and happiness. Similarly, controlling for a large number of potential confounders and measuring different aspects of well being (seven independent measures of well being) and socioeconomic status in a big random sample of British adults, Blanchflower, Oswald, and Stewart-Brown (2012) found a strong positive and monotonic correlation between vegetable and fruit consumption and well being (Blanchflower et al., 2012).”
A 2015 New Zealand study 7 looked at the findings of the earlier large -scale UK study 2 and commented that: “... in a large sample of over 80,000 British people, a dose-response relationship was found between daily servings of FV and both life satisfaction and happiness. People who consumed 7 or 8 portions of FV per day reported the highest life satisfaction and happiness (Blanchflower et al., 2012). These associations remained significant when controlling for demographic and health factors including employment status, income, social class, education, major illness, exercise, smoking, and body mass index (BMI). The findings of Blanchflower and colleagues (2012) are also consistent with other correlational studies showing associations between FV consumption and greater happiness in students (Piqueras, Kuhne, Vera-Villarroal, van Straten, & Cuijpers, 2011), optimism (Boehm, Williams, Rimm, Ryff, & Kubzansky, 2013; Giltay, Geleijnse, Zitman, Buijsse, & Kromhout, 2007; Kelloniemi, Ek, & Laitinen, 2005), peacefulness (Blank, Grimsley, Goyder, Ellis, & Peters, 2007), improved self-esteem and self-efficacy (Brug, Lechner, & De Vries, 1995; Elfhag, Tholin, & Rasmussen, 2008; Steptoe et al., 2003) and higher state positive affect (White, Horwath, & Conner, 2013).”
So the more FV you eat, the happier you are – or, perhaps, the happier you are, the more FV you eat! We are now able to see a good link between the two, but which causes the other? A 2014 US study 8 , as well as an earlier 2010 US study 9 have already shown that if you’re in a good mood, you’ll probably choose the good food (i.e. an apple instead of a greasy doughnut). That is, if you feel good about life, you’ll be more well-equipped to resist the temptation of eating junk food; whilst the converse appears to be true – chronic disease leads to a greater likelihood of eating unhealthy food. But, before we look at answering this chicken and egg (or cheerful and egg-plant) relationship, we need to have at least an idea of what’s going on in our bodies/minds when we eat (or don’t eat) lots of FV.
Which mechanisms are involved?
Agreeing that here’s some good evidence of a relationship (although not yet causal) between FV and happiness does not explain the mechanisms involved.
But a 2013 US study 10 goes some way to explaining this, by concluding that: “Optimism was associated with greater carotenoid concentrations, and this association was partially explained by diet and smoking status.” And these carotenoids (fat-soluble pigments, including beta-carotene, lycopene, lutein, etc) are those wonderful phytochemicals only found in plants, mainly the yellow, orange, or red/purple ones – giving colour to plants and antioxidant/anti-carcinogenic/anti-inflammatory protection to us. This is added to by 2015 New Zealand study 7 which went into a bit more detail about the mechanisms, stating that: “Many FV contain higher levels of vitamin C, an important co-factor in the production of dopamine (Girbe, Ramassamy, Piton, & Costentin, 1994; Seitz et al., 1998). Dopamine is a neurotransmitter that underlies motivation and promotes engagement ‘by adding attraction or zest to life’ (Kringelbach & Berridge, 2009, p. 479). FV also contain B vitamins and complex carbohydrates that promote the synthesis of neurotransmitters involved in mood, including dopamine and serotonin (Rao et al., 2008; Rooney et al., 2013; Stough et al., 2011; Wurtman et al., 2003). B vitamins play a further role in mitochondrial energy function, which could stimulate feelings of vitality and engagement (Depeint et al., 2006). Lastly, antioxidants in FV, such as vitamins E, C, and serum carotenoids [mentioned above], are known to reduce bodily inflammation (McMartin et al., 2013). Lower inflammation is thought to protect against depression (Berk et al., 2013) and has been linked to higher levels of eudaemonic well-being (Friedman, Hayney, Love, Singer, & Ryff, 2007).”
So is it simply that being physically healthy (partly because of the positive effects of all these carotenoiods and vitamins) makes us happy? Not at all. There are plenty of physically healthy people who are far from happy and, conversely, there are people who are not in the best of health who are able to remain pretty happy. Of course, being healthy must be a significant plus in all cases, helping us towards a higher level of personal happiness.
The latter study found that there was a day-by-day relationship between FV intake and happiness – that is, the participants reported higher levels of happiness on the days they ate more FV. The researchers concluded: “When people ate more FV, they reported greater eudaemonic well-being, greater curiosity, and more creativity in their daily lives. These findings suggest that FV intake is related to other aspects of human flourishing, beyond just feeling happy. These results are important because eudaemonic well-being is thought to play an important role in psychological resilience (Steger, Kashdan, & Oishi, 2008). Curiosity has also been linked to greater resilience (Kashdan, 2009). Although at this stage, we cannot say that eating carrots will make you more curious or that eating fruit will help you flourish, our results provide a first line of evidence by showing between- and within-person associations between these states.”
Chicken or egg? Mood or food?
So, going back to the issue of which causes the other (i.e whether eating good food makes you happy or being happy makes you eat good food), we need to know whether eating FV today will affect your mood tomorrow. That would give a really good indication of which comes first…and, luckily enough, there is a 2013 UK study 11 which looked precisely at this time-lagged test to see which came first – eating good food (FV) or feeling good. The researchers concluded that: “Results of lagged analysis showed that fruits and vegetables predicted improvements in positive affect the next day, suggesting that healthy foods were driving affective experiences and not vice versa.”
Further research will be needed to support this finding, as well as a wide-dispersal of the findings into the public arena, before there’s a quantum change in people’s behaviour – that is, choosing a bowl of peaches instead of a bottle of Prozac!
So it looks like the evidence suggests 7+ daily servings of FV produces a tangible result. If you’re only eating whole plant foods, then it’s likely to be difficult not to eat at least this amount; although I would suggest that you try to cram in as much whole fresh fruit and veg as possible, including, of course, the other members of Dr Fuhrman’s G-BOMBS 12 – beans, onions, mushrooms, berries and seeds/nuts.
For my part, I am quite convinced that the relationship between FV and happiness is one of mutual positive feedback. That is, eating FV increases happiness and, at the same time, increased happiness leads to eating more FV and less harmful comfort food. I mean, as Dr Greger points out in his article 13 and video 14 on this subject, who needs to eat comfort food when you’re already comforted by your food?
- C Rooney, M C McKinley, J V Woodside. The potential role of fruit and vegetables in aspects of psychological well-being: a review of the literature and future directions. Proc Nutr Soc. 2013 Nov;72(4):420-32.
- D G Blanchflower, A J Oswald, S Stewart-Brown. Is Psychological Well-being Linked to the Consumption of Fruit and Vegetables? NBER Working Paper No. 18469
- Definition of eudaimonia – Wikipedia
- S Y Kye, K Park. Health-related determinants of happiness in Korean adults. Int J Public Health. 2014 Oct;59(5):731-8.
- J A Piqueras, W Kuhne, P Vera-Villarroel, A van Straten, P Cujipers. Happiness and health behaviours in Chilean college students: a cross-sectional survey. BMC Public Health. 2011 Jun 7;11:443.
- M Fararouei, I J Brown, M A Toori, R E Haghighi, J Jafari. Happiness and health behaviour in Iranian adolescent girls. J Adolesc. 2013 Dec;36(6):1187-92.
- T S Conner, K L Brookie, A C Richardson, M A Polak. On carrots and curiosity: eating fruit and vegetables is associated with greater flourishing in daily life. Br J Health Psychol. 2015 May;20(2):413-27.
- M P Gardner, B Wansink, J Kim, S Park. Better moods for better eating?: How mood influences food choice. Journal of Consumer Psychology Volume 24, Issue 3, July 2014, Pages 320–335.
- A Fedorikhin, V M Patrick. Positive Mood and Resistance to Temptation: The Interfering Influence of Elevated Arousal. Journal of Consumer Research, Vol. 37, No. 4, 2010.
- J K Boehm, D R Williams, E B Rimm, C Ryff, L D Kubzansky. Association between optimism and serum antioxidants in the midlife in the United States study. Psychosom Med. 2013 Jan;75(1):2-10.
- B A White, C C Horwath, T S Conner. Many apples a day keep the blues away–daily experiences of negative and positive affect and food consumption in young adults. Br J Health Psychol. 2013 Nov;18(4):782-98.
- Dr Fuhrman’s G_BOMBS
- How Many Servings of Fruits and Vegetables to Improve Mood? Written By Michael Greger M.D. FACLM on September 4th, 2018
- Which Foods Increase Happiness? Michael Greger M.D. FACLM February 22nd, 2016 Volume 29