Researchers at the University of Toronto found that a lower intake of fruits and vegetables was associated with a higher incidence of depression in both men and women. The same study also found that middle-aged and older women who immigrated to Canada were more likely to suffer from depression compared to Canadian-born women.

Fruits and vegetables are rich in various minerals and vitamins that are known to reduce the plasma concentrations of C-reactive protein, which is associated with low-grade inflammation.

Important nutrients affect brain chemistry, impacting mood, memory and cognitive function. Take a moment to realize that about 95% of your serotonin — the neurotransmitter that regulates sleep and appetite, but also mediates mood and inhibits pain — is produced in the gastrointestinal tract, which, by the way, is lined with over a hundred million nerve cells.

What’s more, simply eating at regular intervals, regardless of the food you intake, can have a significant impact. Research carried out by the University of Illinois Extension found that eating regular meals and snacks at the same time every day helps keep your blood sugar levels steady, which also helps keep your mood steady.

The researchers analyzed data from the Canadian Longitudinal Study, which involved 27,162 men and women aged 45 to 85 years, of whom 4,739 are immigrants.

The results suggest that men were more likely to experience depression if their diet consisted of high-fat food and lower levels of omega-3 eggs. The low intake of fruits and veggies was linked to depression in both men and women. Additionally, lower grip strength was also associated with depression.

“We were interested to learn that omega-3 polyunsaturated fats were inversely associated with depression among men.” said co-author Yu Lung, a doctoral student at University of Toronto’s Factor-Inwentash Faculty of Social Work (FIFSW). “Future research is needed to explore the pathways but it is plausible that increased omega-3 fatty acid concentration in the diet may influence central nervous system cell-membrane fluidity, and phospholipid composition, which may alter the structure and function of the embedded proteins and affect serotonin and dopamine neurotransmission.”

The Canadian researchers note that these findings highlight the mind-body connection, where an unhealthy body can cause changes in mood and brain chemistry, and vice-versa. The Canadian researchers found, for instance, that depression was associated with experiencing chronic pain and at least one chronic health condition.

For immigrant women, the study also found a higher likelihood of experiencing depression when compared to Canadian-born women. Interestingly, this connection did not apply to men.

“The older immigrant women in this study may have reported depression as a result of the substantial stress associated with settling in a new country such as having insufficient income, overcoming language barriers, facing discrimination, adapting to a different culture, reduced social support networks, and having their education and work experiences unrecognized,” said Professor Esme Fuller-Thomson, senior author of the paper.

“Although we did not have the data to explore why there was a gender difference, it may be that in these older married couples it was the husband who initiated the immigration process and the wives may not have as much choice about whether or not they wanted to leave their homeland, said co-author Dr. Karen Kobayashi, Associate Dean Research and Graduate Studies in the Faculty of Social Sciences.

The findings, which were published in the journal BMC Psychiatry, could define programs and policies that might help immigrants ease their transition to a new country.

This isn’t the first study to highlight the importance of a healthy diet for mental health. Previously, other research groups showed that eating a healthy diet rich in fruit, vegetables, fish, and lean meat, is associated with reduced risk of depression