by Bianca Garilli, ND and Ashley Jordan Ferira, PhD, RDN
Poor diet quality is common in developed countries and is responsible for significant morbidity and mortality. The impact of dietary patterns and nutritional bioactives on mental health is important to understand since at least 16 million people in the US, or 7% of the population, experience at least one bout of depression per year.1 The worldwide prevalence of depression is estimated to be 300 million, with projections by the World Health Organization identifying unipolar major depression as the leading cause of global disease burden by the year 2030.2-3
Various approaches focused on improving mental health exist in the medical community, from prescription medications to exercise. Since food impacts mood, and mood likely impacts food choice, it makes sense that nutrition and dietary components would be researched for their impact on mental health.
Fruit and vegetable (F&V) intake has a considerable body of scientific research related to mental health. A 2016 meta-analysis that included 18 studies (totaling 400,000+ participants) assessed the association between F&V intake and depression; this large analysis revealed an inverse relationship between F&V consumption and risk of depression.4 Additionally, a 2018 systematic review and meta-analysis demonstrated a linear, inverse association between F&V intake and depression risk.5 Each 100g increase in fruit or vegetable intake was associated with a 3% risk reduction for depression.5 These collective findings provide evidence for the protective nature of F&V intake on depression.5
Americans and Western diet-consumers have significant room for improvement when it comes to F&V intake. The 2015-2020 Dietary Guidelines for Americans recommends adults take in 1.5-2 cups of fruit/day and 2-3 cups of vegetables/day,6 but only 12% and 9% of US adults meet these fruit and vegetable recommendations, respectively.7 While this food group gap is clear, less is known regarding the best form to consume F&V for optimal health benefit – should they be eaten raw, or are they just as beneficial when consumed in prepared forms, such as being cooked (steamed, boiled, baked, etc.) or canned?
A recent study with a cross-sectional survey design was conducted to learn more about associations between raw vs. processed F&V and mental health symptoms in young adults.8 Participants included 422 adults living in the US and New Zealand ages 18-25 (66.1% female; average BMI: 24.8; 67.5% Caucasian).8 An online survey gleaned data on typical consumption of raw vs. cooked/canned/processed F&V and also captured information pertaining to mental health (i.e., symptoms of depression, anxiety, negative mood, positive mood, life satisfaction and flourishing), as well as pertinent covariates including socioeconomic status, BMI, sleep, physical activity, smoking, and alcohol use.8
Participants only consumed ~3.2 daily servings of F&V on average.8 The following correlations were found:8
- The consumption of raw F&V had the strongest associations with most of the positive mental health measures
- Raw F&V intake was associated with fewer depressive symptoms and higher positive mood, life satisfaction, and flourishing
- Raw fruit consumption was also associated with reduced negative mood
- The top raw F&V correlated with better mental health included: carrots, bananas, apples, citrus fruits, fresh berries, kiwifruit, lettuce, dark leafy greens, and cucumber
- Processed F&V intake, on the other hand, was only associated with positive mood but not with any of the other mental health variables
- An additional interesting finding unrelated to F&V intake was that higher soda consumption was correlated with more depressive symptoms and lower life satisfaction
After adjusting for the aforementioned covariates (and performing hierarchical regression statistics analyses to ascertain predictive information), results included:8
- Raw F&V intake predicted significantly lower depressive symptoms and higher positive mood, life satisfaction, and flourishing; these beneficial associations were not found for processed F&V intake
- Incremental, step-wise improvements in positive mood were observed up to 6.5 servings of raw F&V per day; >6.5 servings/day was not associated with additional benefits
- Raw F&V intake is more strongly related to positive, rather than negative mental health
Why is this Clinically Relevant?
- F&V represent a nutrient dense food group and “gap” for many Americans.7
- F&V consumption has been associated with reduced risk of chronic diseases, including cardiovascular disease and certain types of cancer9
- It is important to achieve daily intake of a variety of F&V for good nutrition and health, including mental health4-5,8
- It may be particularly valuable to recommend the daily intake of raw F&V to support positive mental health in young adults; more research is warranted in this area8
- Some F&V may have higher nutritional value and bioavailability in raw vs. processed forms
- By consuming a variety of F&V, one benefits from diverse traditional nutrients (macro- and micronutrients) and phytonutrients/phytochemicals, working synergistically to protect against disease9
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- NIH. National Institute of Mental Health. Major depression among adults.http://www.who.int/news-room/fact-sheets/detail/depression. Accessed June 19, 2018.
- WHO. Depression. http://www.who.int/news-room/fact-sheets/detail/depression. Accessed June 19, 2018.
- Lépine JP, Briley M. The increasing burden of depression. Neuropsychiatr Dis Treat. 2011;7(Suppl 1):3–7.
- Liu X, Yan Y, Li F, Zhang D. Fruit and vegetable consumption and the risk of depression: A meta-analysis. Nutrition. 2016;32(3):296-302.
- Saghafian F, Malmir H, Saneei P, Milajerdi A, Larijani B, Esmaillzadeh A. Fruit and vegetable consumption and risk of depression: accumulative evidence from an updated systematic review and meta-analysis of epidemiological studies. Br J Nutr. 2018;119(10):1087-1101.
- USDHHS and USDA. 2015-2020 Dietary Guidelines for Americans. https://health.gov/dietaryguidelines/2015/guidelines/. Accessed June 22, 2018.
- CDC. State Indicator Report on Fruits and Vegetables, 2018. https://www.cdc.gov/nutrition/downloads/fruits-vegetables/2018/2018-fruit-vegetable-report-508.pdf. Accessed June 22, 2018.
- Brookie KL, Best GI, Conner TS. Intake of raw fruits and vegetables is associated with better mental health than intake of processed fruits and vegetables. Front Psychol. 2018;9:487.
- PBH Foundation. Fruit + Veggie Connection. https://pbhfoundation.org/sites/default/files/pdf/FVConn_Issue3_finalWEB_1409930945.PDF. Accessed June 25, 2018.