In 2019, a Canadian study provided very interesting data related to depression. During this study, 27,162 Canadians aged 45 to 85 were interviewed. The researchers collected data on several variables such as depression (the dependent variable under study), age, marital status, consumption of fruits and vegetables, etc. They performed statistical calculations using cross-sectional data, taken at the same precise moment and not at various points in time.
Let’s see what they found out!
Fruit and vegetable consumption
The researchers noted that the risk of depression was higher among participants consuming a small amount of fruits and vegetables. Whereas for men who consumed 3 to 6 servings per day, were found to have reduced risks.
This is not surprising when we know that in 2013, a meta-analysis (the analysis of a large number of published studies) had shown that healthy eating, in adults, was associated with a lower probability of suffering from depression (Lai et al., 2013). According to another meta-analysis, also published in 2013, the Mediterranean diet, which promotes a diet rich in fruits and vegetables, reduces the risk of experiencing depression by 30% (Psaltopoulou et al., 2013).
The authors of the Canadian study point out that there are mechanisms of action that can explain the influence of the consumption of fruits and vegetables on mood. Here’s a good example: fruits and vegetables provide compounds with anti-inflammatory properties. On the other hand, we know that depression is linked to markers of inflammation.
A mechanism of action that was not addressed in this study: the influence of fruits and vegetables on our good intestinal bacteria (microbiota). Indeed, fruits and vegetables provide us with fibers, also called prebiotics, which nourish the good bacteria housed in our intestine. These good bacteria, when properly fed, produce health-promoting chemical molecules, some of which would help fight inflammation.
Some studies have shown a link between the imbalance of the microbiota and psychological problems (e.g. depression). Rodent experiments have shown that an improvement or deterioration of the microbiota results in changes, favorable or unfavorable, in behavior.
Other factors associated with depression?
The study also allowed, through statistical analyses, to demonstrate the link between depression and other variables. Here is a summary:
- Salty snacks – processed and overly salty – and pure fruit juices are associated with depression in women.
- It was noted that people living with chronic pain or a chronic disease were more likely to suffer from depression. Examples of chronic diseases considered in the study: Crohn’s disease, heart disease, epilepsy, migraine, rheumatoid arthritis, etc.
- Without saying that it is absolutely necessary to be in a relationship to be happy, men in a relationship would be less likely to suffer from depression.
- Level of education was a variable associated with depression. Specifically, women who did not complete high school were more likely to experience depression, while men would see their risk reduced if they completed post-secondary education.
- For women, more factors appeared to be related to depression. Researchers hypothesize that women are more susceptible to inflammation and autoimmune responses that increase the risk of depression.
The study does not conclude that eating fruits and vegetables fights depression, but various biological mechanisms help explain the possible effect of food on depression and mood. It is interesting to remember that certain diets featuring fruits and vegetables, such as the Mediterranean diet, have been linked to a decreased risk of depression.
Written by: Stéphane Migneault, psychologist
Scientific popularization: Stéphanie Paré
- Davidson, K. M., Lung, Y., Lin, S. Tong, H. et al. (2019). Depression in middle and older adulthood: the role of immigration, nutrition, and other determinants of health in the Canadian longitudinal study on aging. BMC Psychiatry, 19, 239.