When I was a kid, and for basically my entire life, having a (huge) slice of watermelon – or two or three, made me happier than eating cake. Yeah, watermelon made me happy. But could eating more fruit – and veggies – make you less depressed? Some new research says that’s not a far-fetched notion.
This review in the American Journal of Clinical Nutrition evaluated the body of studies that investigated the effects of eating fruits and vegetables on various measures of mental health. The authors wanted to see if an actual causal relationship existed, so they looked at both experimental studies and observational studies.
This review included studies that reported fruits and vegetables together, as well as those that looked only at intakes of vegetables or fruits. Being this specific really pared down the pool of eligible studies, but they did find ten that met the criteria, and these included over 33,000 people.
The authors concluded that increased fruit and vegetable consumption had a “positive effect on psychological well-being”, with vegetables having somewhat more impact than fruits, in studies that looked at the effects independently. The effect on mental health however, was less clear.
Basic Brain Chemistry
There may be some chemical reasons for the improved mental outlook from eating more produce. Fruits and vegetables are loaded with micronutrients like vitamin C and B-complex vitamins, that influence the formation of neurotransmitters, such as serotonin, dopamine, and norepinephrine in the brain.
Neurotransmitters are known to influence our mood and impact mental health. Indeed, many medications that treat depression are focused on modulating neurotransmitters like serotonin, to optimize their impact on mental health, depression, and psychological well-being.
Chicken vs. Egg
My first response was, “did the fruit and vegetable consumption improve their psychological well-being, or was their consumption of fruits and vegetables higher just because they had a better sense of well-being in the first place. The latter would be called “reverse causality”.
The amount of fruits and vegetables needed for “meaningful changes” varied among studies, ranging from 3.7 servings to 7-8 servings. Counting a typical “serving” as about ½ cup, you’re looking at from 2-4 cups per day to have an effect. This is well within recommended amounts by pretty much all global health authorities.
While this review didn’t include clinical research, a 2017 clinical study looked directly at the impact of increasing adherence to a “modified-Mediterranean” diet, which emphasizes fruit and vegetable consumption, as adjunctive treatment in persons diagnosed with moderate to severe depression. Scores on the Montgomery–Åsberg Depression Rating Scale (MADRS) were used as a measure of the severity of depression. This study checked some important boxes for quality of design:
- Randomized controlled trial.
- Parallel groups.
- Some received regular nutrition counseling on a modified Mediterranean diet, others received social support on the same schedule.
Result: The dietary intervention group had significantly improved scores. Even better, 32% of the dietary intervention group achieved remission of their depression, vs 8% in the social support group, and these results were statistically significant.
The dietary group also at significantly more:
- Dairy foods
- Pulses (beans, peas)
They also ate fewer servings of less nutritious items, like sweets and, empty-calorie foods.
The study lasted only 12 weeks, so further research that addresses longer term results and with larger groups, is certainly warranted. Still, given a relatively simple intervention that just encourages people to eat a diet that’s balanced and includes what they need anyway, it’s hard to dismiss the value of results.
Cut-to the-Chase Take-Away
Aa clinician, I care mostly about people eating as many of each as possible and I’m less fussy about fruits vs. veggies. None of them are nutritious unless you eat them and all of them are good for us. Eat the ones you like and eat them daily. You’ll certainly be happier with your choices!