By: Dr. Kathleen Regan, ND

In the coming decade, we will see more and more attention focused on the role of food in brain chemistry. Studies have shown that ‘higher intake of fish, fruit and vegetables is associated with lower incidence of mood disorders’ (1).  The United Kingdom (UK) is a world leader in this research initiative of connecting what we eat with how we feel.

One of the more recent studies to come out of the UK looked at the relationship between well-being and the consumption of fruit and vegetables by drawing data from the UK Household Longitudinal Study (UKHLS) which includes information collected from 50,000 people between 2009-2017. In this ‘Lettuce Be Happy’ study, the authors concluded:

  • Increased fruit & vegetable consumption can enhance mental well-being.
  • Increasing how frequently you consume fruit and vegetables is as important as the overall quantity you consume.
  • The relationship between food and mental health is meaningful and significant across different measures of well-being.

This study controlled for many variables including age, gender, income, employment etc. and the cause and effect between food and mood was still there! In fact, the authors noted that ‘moving from unemployment to employment has an equivalent effect on life satisfaction as increasing consumption of fruits and vegetables by approximately 10.5 portions per day’ (2).

The findings of this study are not unique. A similar study from Australia in 2016 demonstrated that increased fruit and vegetable consumption was ‘predictive of increased happiness, life satisfaction, and well-being’; improvements occurred within 24 months (3).

What is shocking is how few fruits and vegetables the average person consumes. Statistics Canada reported in 2017:

  • Only 28.6% of Canadians aged 12 and older (roughly 8.3 million people) reported that they had consumed fruits and vegetables five or more times per day.
  • Since 2015, the proportion of Canadians reporting that they have consumed fruits and vegetables five or more times per day has been decreasing (31.5% in 2015 and 30.0% in 2016).
  • Females were more likely than males to report consuming fruits and vegetables five or more times per day (34.7%, 22.3%).


Obviously, there is hopeful room for improvement using diet as an intervention for mental health and wellness. But first, why are fruits and vegetables so important?

The ‘Lettuce Be Happy’ authors cite research which suggests that:

  • The antioxidant properties in vitamin C and E mitigate oxidative stress and lower inflammatory markers which have been associated with the onset of depressive mood
  • B-vitamins help maintain mitochondrial function and dysfunction associated with stress and anxiety.
  • The positive effects of fruit and vegetable consumption could also be partly due to increased carbohydrate intake as carbohydrate-rich foods increase concentrations of brain serotonin.
  • Complex carbohydrates found in fruits and vegetables may enhance positive affect, whereas refined sucrose more commonly found in sweets and sugary soft drinks may worsen mood.
  • Consuming more fruits and vegetables may result in a ‘substitution effect’ OR reduced consumption of other food groups that may be detrimental to well-being.


The authors suggest that future research should measure for the consumption of other foods (e.g., meat, sweets, sugary drinks), as well as overall calories consumed. And indeed, we should measure for this!

More importantly, we should follow the (now global) advice to consume 5-10 servings per day or ‘half of the plate’ as fruit and vegetable.

The World Health Organization announced in 2004 that a minimum of ‘400g of fruit and vegetables per day (roughly 5 servings) excluding potatoes and other starchy tubers’ was beneficial for a range of physical health concerns (4).

This lead the way for a number of countries to launch the 5 A DAY campaign and a number of public health initiatives to encourage increasing the number of fruits and vegetables in daily diets. A 2017 meta-analysis found that consumption of double the minimum recommendation – 800g or 10 a day – provided an increased protection against all forms of mortality (5).

From our current understanding of food and mood research, mental wellness increases in a linear relationship with the amount of fruit and vegetable consumed but 5 A DAY is a great place to start!


What does this mean in practical terms?

  • 1 Serving = 1 cup of raw loosely packed vegetable/fruit, ½ cup of cooked or steamed vegetable, 1 medium ball of fruit
  • Consider your plate from an aerial view and ask yourself, “How can I make 50% of this plate fruit and vegetable?”
  • Prepare, prepare, prepare. Keep your fridge stocked with seasonal, delicious fruit and vegetables and dips or spices to enhance flavour.


How long does it take to notice a difference?

Some research suggests up to 24 months but I have noticed a clinical difference in a much shorter period of time with patients, closer to 12 weeks.



  1. Huang P, O’Keeffe M, Elia C, Karamanos A, Goff LM, Maynard M, Cruickshank JK, Harding S. Fruit and vegetable consumption and mental health across adolescence: evidence from a diverse urban British cohort study. Int J Behav Nutr Phys Act.2019 Feb 8;16(1):19. doi: 10.1186/s12966-019-0780-y. PubMed PMID: 30736801;PubMed Central PMCID: PMC6368762.
  2. Ocean N, Howley P, Ensor J. Lettuce be happy: A longitudinal UK study on the relationship between fruit and vegetable consumption and well-being. Soc Sci Med. 2019 Feb;222:335-345. doi: 10.1016/j.socscimed.2018.12.017. Epub 2019 Jan 7. PubMed PMID: 30626498; PubMed Central PMCID: PMC6381324.
  3. Mujcic R, J Oswald A. Evolution of Well-Being and Happiness After Increases in Consumption of Fruit and Vegetables. Am J Public Health. 2016 Aug;106(8):1504-10. doi: 10.2105/AJPH.2016.303260. PubMed PMID: 27400354; PubMed Central PMCID: PMC4940663.
  4. Agudo, A. 2005. Measuring intake of fruit and vegetables. Background Paper for the Joint FAO/WHO Workshop on Fruit and Vegetables for Health, 2004, Kobe, Japan. WHO, Electronic Resource
  5. Aune D, Giovannucci E, Boffetta P, Fadnes LT, Keum N, Norat T, Greenwood DC, Riboli E, Vatten LJ, Tonstad S. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality-a systematic review and dose-response meta-analysis of prospective studies. Int J Epidemiol. 2017 Jun; 46(3):1029-1056. doi: 10.1093/ije/dyw319. Review. PubMed PMID: 28338764; PubMedCentral PMCID: PMC5837313.