A healthy gut helps you digest your food and absorb its nutrients, strengthens your immune system and reduces your risk of certain chronic diseases.
But not everyone realizes that having a happy belly also has a major impact on your mood since about 90% of your body’s serotonin and over 50% of your dopamine — two crucial neurotransmitters responsible for making you feel good — are produced in your gut.
For this reason, scientists often call the gut “the second brain.”
And while an apple a day may keep the doctor away, research shows an orange a day might keep the blues at bay.
Dr. Raaj Mehta, a physician and instructor at Harvard Medical School, and his colleagues analyzed the data of over 30,000 women and found that those who consumed a lot of citrus were much less likely to develop depression than those who didn’t.
Their findings were published late last year in the journal Microbiome.
“We found that eating one medium orange a day may lower the risk of developing depression by about 20%,” Mehta told the Harvard Gazette last month.
“And the effect seems to be specific to citrus. When we look at people’s total fruit or vegetable consumption, or at other individual fruits such as apples or bananas, we don’t see any relationship between intake and risk of depression.”
Using stool samples, researchers discovered eating more citrus was associated with increased levels of a beneficial gut bacterium called Faecalibacterium prausnitzii (F. prausnitzii), which is known for its anti-inflammatory properties but might also help serotonin and dopamine make their way to the brain.
A study published in 2022 found that eating fewer citrus fruits was clearly associated with a heightened risk of depression in patients with chronic health failure.
However, Mehta noted that it’s “hard to compare the effectiveness of citrus to traditional antidepressants…because we’re talking about preventing depression, and those drugs are usually used to treat depression once a person is already experiencing it.”
The researchers also acknowledged that their study had certain limitations, as most of the participants were white, middle-aged women; additionally, while they controlled for several factors, there’s still the possibility that their findings were correlational rather than causal.
Still, eating an orange — or lemon or grapefruit, if that’s what you prefer — a day certainly can’t hurt, and the study sheds light on the relationship between the gut and the brain, as well as the role these fruits play on it.
“I hope our results inspire other researchers to look into the link between diet and mental health,” Mehta said. “I think people know intuitively that the foods we eat impact our mood. We even have a term for this: comfort foods, which make ourselves feel better in the short term.”
“There’s such a huge unmet need for depression treatments, and eating citrus doesn’t really have any major side effects,” he added, “so it would be great to see how much this simple treatment can help.”
