A new study involving twins from the US, Denmark, Australia, and Sweden suggests a strong link between diet and mental health, particularly in older adults. This large-scale research could be one of the most significant indicators yet of how nutrition influences mental wellness as we age.
The researchers followed 1,741 pairs of twins over 11 years, investigating their fruit and vegetable consumption, health status, body weight, and overall mental wellness. In total, 3,483 individuals took part in the studies, each over the age of 45 at the baseline, providing insights into how diet affects mental health into later life—a topic often overlooked compared to research on younger populations.
Each study had slightly different measures, with some not tracking weight over time, for example. Nevertheless, the core focus remained on dietary habits, mental health, and how these interacted over time. Participants were surveyed about their eating habits, particularly their intake of fruits such as bananas, oranges, apples, and pears, as well as salads, cooked vegetables, and raw vegetables. Potato consumption was recorded separately as an additional measure.
They also monitored symptoms of depression using surveys conducted within each of the four separate studies. Across all groups, higher fruit and vegetable intake was consistently associated with better mental health outcomes. Although the researchers did not quantify precisely how much impact fruit and vegetable consumption had on mental health, the association was clear.
The researchers adjusted their findings to account for factors like age, sex, education, living arrangements, and BMI, where these measurements were available. They concluded that these variables had little influence on the relationship between diet and depression, stating, "the addition of BMI, physical health, and cognitive ability to the model had minimal impact on results. This suggests the exclusion of participants is unlikely to have impacted the results."
Dr Annabel Matison, the lead author of the study, believes the findings offer a compelling argument for increasing fruit and vegetable consumption among adults over the age of 45. She suggested that improving nutrition could be a valuable addition to traditional treatment approaches like counselling or medication for those living with depression.
Dr Karen Mather, co-author of the research, underscored the strength of the study’s methodology, highlighting that twin studies are often regarded as the gold standard of research due to their ability to compare participants with almost identical DNA.
The research team suggested that better nutrition brings numerous benefits to brain health. Consuming more vitamins and fibre can help nourish the body and maintain healthy blood flow to the brain. Furthermore, a diet rich in fresh produce is thought to promote a healthy gut microbiome, which may, in turn, play a role in maintaining mental health by keeping the mind more settled.
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