A randomized controlled trial investigates diet and psychological well-being.
Fruits and Vegetables Put to the Test for Boosting Mood
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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
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 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.” Okay, 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 [type of] family upbringing [that] might lead people simultaneously to eat in a healthy way and also to have better mental well-being, so that diet is then 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 Fruit 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 recommendation is 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. Okay, but “Does eating fruits and [veggies] also reduce the… risk of depression and anxiety?” I mean well-being is nice, but “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 fruit 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 percent reduced risk of depression.” That’s about half an apple, yet “less than 10 percent 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 the great enlightenment philosopher pointed out, just because the cock crows before the 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 is 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 vegetable 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 rewards, 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!
Please consider volunteering to help out on the site.
- Tuck NJ, Farrow C, Thomas JM. Assessing the effects of vegetable consumption on the psychological health of healthy adults: a systematic review of prospective research. Am J Clin Nutr. 2019;110(1):196-211.
- Holder MD. The Contribution of Food Consumption to Well-Being. Ann Nutr Metab. 2019;74(Suppl 2):44-51.
- Mujcic R, Oswald AJ. Does eating fruit and vegetables also reduce the longitudinal risk of depression and anxiety? A commentary on 'Lettuce be happy'. Soc Sci Med. 2019;222:346-8.
- Mujcic R, J Oswald A. Evolution of Well-Being and Happiness After Increases in Consumption of Fruit and Vegetables. Am J Public Health. 2016;106(8):1504-10.
- 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;222:335-45.
- 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):1087-101.
- Dreher ML. Whole Fruits and Fruit Fiber Emerging Health Effects. Nutrients. 2018;10(12):1833.
- Conner TS, Brookie KL, Carr AC, Mainvil LA, Vissers MC. Let them eat fruit! The effect of fruit and vegetable consumption on psychological well-being in young adults: A randomized controlled trial. PLoS One. 2017;12(2):e0171206.
- Smith AP, Rogers R. Positive effects of a healthy snack (fruit) versus an unhealthy snack (chocolate/crisps) on subjective reports of mental and physical health: a preliminary intervention study. Front Nutr. 2014;1:10.
Video production by Glass Entertainment
Motion graphics by Avo Media
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
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 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.” Okay, 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 [type of] family upbringing [that] might lead people simultaneously to eat in a healthy way and also to have better mental well-being, so that diet is then 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 Fruit 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 recommendation is 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. Okay, but “Does eating fruits and [veggies] also reduce the… risk of depression and anxiety?” I mean well-being is nice, but “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 fruit 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 percent reduced risk of depression.” That’s about half an apple, yet “less than 10 percent 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 the great enlightenment philosopher pointed out, just because the cock crows before the 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 is 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 vegetable 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 rewards, 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!
Please consider volunteering to help out on the site.
- Tuck NJ, Farrow C, Thomas JM. Assessing the effects of vegetable consumption on the psychological health of healthy adults: a systematic review of prospective research. Am J Clin Nutr. 2019;110(1):196-211.
- Holder MD. The Contribution of Food Consumption to Well-Being. Ann Nutr Metab. 2019;74(Suppl 2):44-51.
- Mujcic R, Oswald AJ. Does eating fruit and vegetables also reduce the longitudinal risk of depression and anxiety? A commentary on 'Lettuce be happy'. Soc Sci Med. 2019;222:346-8.
- Mujcic R, J Oswald A. Evolution of Well-Being and Happiness After Increases in Consumption of Fruit and Vegetables. Am J Public Health. 2016;106(8):1504-10.
- 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;222:335-45.
- 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):1087-101.
- Dreher ML. Whole Fruits and Fruit Fiber Emerging Health Effects. Nutrients. 2018;10(12):1833.
- Conner TS, Brookie KL, Carr AC, Mainvil LA, Vissers MC. Let them eat fruit! The effect of fruit and vegetable consumption on psychological well-being in young adults: A randomized controlled trial. PLoS One. 2017;12(2):e0171206.
- Smith AP, Rogers R. Positive effects of a healthy snack (fruit) versus an unhealthy snack (chocolate/crisps) on subjective reports of mental and physical health: a preliminary intervention study. Front Nutr. 2014;1:10.
Video production by Glass Entertainment
Motion graphics by Avo Media
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Fruits and Vegetables Put to the Test for Boosting Mood
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
For more on mood foods and other interventions, see:
- Anti-Inflammatory Diet for Depression
- Plant-Based Diets for Improved Mood and Productivity
- Antioxidants and Depression
- Do Antidepressant Drugs Really Work?
- Exercise vs. Drugs for Depression
- Gut Feelings: Probiotics and Mental Health
- Fighting the Blues with Greens?
- Best Food for Antidepressant-Induced Sexual Dysfunction
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