Eating an orange a day may lower depression, stress —Experts

Oranges are popular due to their natural sweetness, the many different types available, and the diversity of uses. Individuals consume them in juices and marmalades, eat them whole, use their peel to add a tangy flavour to cakes and desserts or burn it as an insect repellant.

Although it is particularly known for its vitamin C content, oranges contain other substances that may reduce inflammation and work against many other diseases like depression.

Globally, depression is a major public health concern. According to the World Health Organisation (WHO), it is the largest contributor to the non-fatal burden of disease, with more than 80 per cent of this burden represented across low- and middle-income countries.

According to a recent study, eating an orange every day may reduce a person’s risk of developing depression by 20 percent because the citrus fruit promotes the growth of bacteria called Faecalibacterium prausnitzii (F. prausnitzii), which are gut-based microorganisms that affect the synthesis of the mood-enhancing chemicals serotonin and dopamine.

The study, led by Raaj Mehta, an instructor in medicine at Harvard Medical School and a physician at Massachusetts General Hospital, was based on the data set of the Nurses’ Health Study II (NHS2). It began in 1989 intending to find risk factors for major chronic diseases in women.

It involves more than 100,000 women, and roughly every two years they provide researchers with detailed information about their lifestyle, diet, medication use, and health.

The researchers had leveraged these data to look for evidence that nurses who ate a lot of citrus had lower rates of future depression than those who did not.

Also, a subset of participants in the NHS2 gave researchers several samples of their stool over a year. Using DNA sequencing results from these stool samples, they looked for links between citrus intake and particular species of bacteria in the gut microbiome.

They found that eating one medium orange a day may lower the risk of developing depression by about 20% and the effect seems to be specific to citrus.

When they look at people’s total fruit or vegetable consumption, or at other individual fruits such as apples or bananas, they don’t see any relationship between their intake and risk of depression.

One unique part of the study is that a subset of participants in the NHS2 gave researchers several samples of their stool over a year.

Using DNA sequencing results from these stool samples, researchers looked for links between citrus intake and particular species of bacteria in the gut microbiome.

Since the NHS2 only included women and the study required men to confirm the findings, they looked to a similar study called the Men’s Lifestyle Validation Study, where they also found that increasing levels of F. prausnitzii were inversely correlated with depression risk scores. One species of bacteria stood out—F. prausnitzii was more abundant in people who were not depressed than in people who were, and eating a lot of citrus was also associated with high levels of F. prausnitzii.

The researchers said it is hard to compare the effectiveness of citrus to traditional antidepressants, such as selective serotonin reuptake inhibitors, because we are talking about preventing depression, and those drugs are usually used to treat depression once a person is already experiencing it.

However, in the future, they suggested more research to be able to conclude that eating citrus could perhaps be part of a strategy for managing depression that also involves these more traditional pharmaceuticals.

New research led by postdoctoral fellow Annabel Matison from UNSW Sydney’s Centre for Healthy Brain Ageing (CHeBA) published in the Journal of Affective Disorders also said eating more fruit may reduce the risk of depression.

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They examined the associations between fruit and vegetable intake and depression in adults 45 years and older. The participants came from multiple regions across six continents, including the United States, Sweden, Brazil, Nigeria, Malaysia and Australia.

The researchers assessed 7,801 community-based adults without depression and revealed a beneficial association between higher fruit intake and lower risk of depression over nine years.

According to a different study from Edith Cowan University (ECU), those who consume more fruits and vegetables experience less stress than those who consume less. They found that those who consumed at least 470 grammes of fruits and vegetables per day experienced 10% less stress than those who consumed less than 230 grammes.

The study looked at the relationship between stress levels and fruit and vegetable consumption in over 8,600 Australians between the ages of 25 and 91 who were taking part in the Baker Heart and Diabetes Institute’s Australian Diabetes, Obesity and Lifestyle (AusDiab) Study.

As fruits and vegetables contain varying nutrients, it also seems likely that different types of fruits and vegetables may have differing impacts on the risk of depression. The evidence for citrus fruits and green leafy vegetables being associated with improved mental well-being is particularly strong.