If an apple a day keeps the doctor away, then a new study suggests upsizing this to a fruit salad may offer even more – by significantly lowering the risk of depressive symptoms with age. It's the latest in a growing body of evidence that points to the long-lasting and wide-reaching health benefits of incorporating fruit into any diet.
Researchers from the National University of Singapore (NUS) looked into the data of 13,738 participants over almost two decades and found that people who ate around three servings of fruit a day, or more, during midlife had an estimated 21% lower risk of developing "depressive symptoms" in the years that followed. And those symptoms included not just being depressed but delayed cognitive function, insomnia, poor concentration and increased fatigue.
The first stage of research took place between 1993 and 1998, when participants with a mean age of 51 were assessed for their daily fruit consumption. Then, in 2014 to 2016, with the mean age of participants now 73, researchers investigated their mental health using the Geriatric Depression Scale. Some 3,180 (23.1%) participants responded as having five or more of the symptoms set out in the survey.
After adjusting for the usual lifestyle factors – smoking, physical activity, sleep quality and other age-related conditions – researchers found that those who consumed three or more servings of fruit a day reported significantly lower depressive symptoms.
“Our study underscores the importance of fruit consumption as a preventive measure against ageing-related depression," said lead researcher Woon-Puay Koh , a professor at NUS Medicine. "In our study population, participants who had at least three servings of fruits a day, compared to those with less than one serving a day, were able to reduce the likelihood of ageing-related depression significantly by at least 21%."
While a Singapore-based study, many of the 14 fruits most commonly consumed are universal, including watermelons, oranges, tangerines, bananas and apples. A serving is generally considered a medium apple or a cup of strawberries.
"This can be achieved by eating one to two servings of fruits after every meal," Koh noted. "We did not see any difference in our results between fruits with high and low glycemic index. Hence, for those with diabetes, they can choose fruits with low glycemic index that will not raise blood sugars as much as those with high index.”
According to the researchers, the key appears to be maintaining fruit intake from ages 40 to 65 years, as a way to simply safeguard mental health in future decades. Just what the link is remains unclear, but they believe the high levels of antioxidants and anti-inflammatory properties found in fruits, like flavonoids, carotenoids and vitamin C, could play a role, reducing oxidative stress and helping to shield the brain from degeneration.
It's also worth noting that vegetable consumption showed no such association between mental health and diet in the 13,738 participants who took part in the study.
“Our study aimed to examine the relationship of midlife consumption of fruits and vegetables with the risk of depressive symptoms in late life," said Koh.
Previous research includes a 2022 Japanese study, which found that fruit, not vegetables, lowered the risk of age-related depression, while a 2021 study from Australia, which looked at participants aged 15-45 years was inconclusive. This latest study is the largest and concentrated instead on 14 fruits in a specific age group across a lengthy time frame.
While focused on Singapore, it supports the findings of American studies, one from 2018 and another from 2021, that found a link between fruit consumption and prevalence of depressive symptoms in adults, with data taken from the US National Health and Nutrition Examination Survey. The 2018 study supposed that consuming bananas could have an additional benefit due to their high concentration of tryptophan, a precursor of serotonin, which plays an important role in mood regulation.
The researchers now plan to look more closely at the association to work out just how fruit may be able to preserve mental health as we age.
The study was published in the Journal of Nutrition, Health and Aging.
Source: National University of Singapore
