Eating more fruit may reduce the risk of depression

Depression is a significant public health problem worldwide. According to the World Health Organization, it is a major contributor to the unpredictable health burden, with more than 80% of this burden occurring in low- and middle-income countries.

A growing body of research suggests that dietary habits, particularly increased consumption of fruits and vegetables, may significantly reduce the risk of depression.

A new study led by postdoctoral fellow Annabel Mathieson from the Centre for Healthy Brain Ageing (CHeBA) at the University of New South Wales in Sydney, published in the Journal of Affective Disorders, is the first to explore the lack of data for older people and people in low- and middle-income countries.

"Compared with depression in younger people, depression in older people has a greater impact on physical performance and cognitive function, and is associated with lower quality of life and increased mortality," explains Mathieson.

"Our aim in this study was to examine the association between fruit and vegetable consumption and depression in people aged 45 years and older."

Participants in the study came from different regions of six continents, including the United States, Sweden, Brazil, Nigeria, Malaysia, and Australia. All data were collected and harmonized from ten long-term studies that are part of the CHeBA-led Cohort Studies of Memory in an International Consortium (COSMIC).

Researchers analyzed data from 7,801 community-based individuals without depression and found a positive association between increased fruit consumption and a reduced risk of depression over a nine-year period.

"This interesting finding, demonstrating a protective association between fruit consumption and the risk of depression, highlights the need for greater attention to diet in public health," notes Mathieson.

Although the results of this study suggested benefits from vegetable consumption, statistically significant findings were not found.

"The reason we found a positive association for fruits but not vegetables may be because vegetables are typically consumed cooked, which may reduce their nutritional value, while fruits are typically eaten raw."

Fruit and vegetable intake was assessed by self-report using comprehensive food frequency questionnaires, short food questionnaires, or dietary history. Depressive symptoms were assessed using validated measures, and depression was defined according to established criteria. Associations between baseline fruit and vegetable intake and the development of depression over a three- to nine-year follow-up period were analyzed using Cox regression.

It is suggested that the high levels of antioxidants, dietary fiber, and vitamins found in fruits and vegetables may have a positive effect on depression through various mechanisms, such as their role in inflammation, oxidative stress, and gut microbiota. Because fruits and vegetables contain different nutrients, it is likely that different types of fruits and vegetables may have different effects on depression risk. The evidence that citrus fruits and green leafy vegetables are associated with a lower risk of depression is particularly strong.

CHeBA co-director and study co-author Professor Henry Brodaty said further research taking into account consumption of different types of fruit and vegetables using standardised measures and focusing on larger numbers of older people, particularly in low- and middle-income countries, was certainly warranted.

"Extending current research into genes associated with food intake represents a promising avenue for influencing fruit and vegetable consumption," says Professor Brodati.

"The types of fruits and vegetables consumed should also be taken into account to better understand the relationships involved, and studies should be designed to ensure greater comparability between cohorts," he added.