A new study suggests that eating an orange a day may reduce the risk of depression by 20%. The research, published in Microbiome, found that citrus fruits may promote the growth of a beneficial gut bacteria called Faecalibacterium prausnitzii (F. prausnitzii), which could influence brain chemicals linked to mood.
How the Study Was Conducted
The study was led by Raaj Mehta, a physician at Massachusetts General Hospital and an instructor at Harvard Medical School. His team analyzed data from the Nurses’ Health Study II (NHS2), a long-term research project involving over 100,000 women.
Every two years, participants reported details about their diet, lifestyle, and health, allowing researchers to track patterns over time.
The study found that women who regularly ate citrus fruits—especially oranges—had a significantly lower risk of developing depression. Interestingly, this link was specific to citrus. Other fruits, like apples or bananas, did not show the same effect.
To confirm the findings, the researchers also examined data from the Men’s Lifestyle Validation Study and observed a similar pattern in men.
The Link Between Gut Bacteria and Mental Health
One unique aspect of the study was that some participants provided stool samples, which allowed researchers to analyze their gut bacteria. They found that people who ate more citrus had higher levels of F. prausnitzii, a bacterium previously linked to good digestive health and lower inflammation.
But how does gut bacteria affect mental health? Researchers believe that F. prausnitzii plays a role in producing serotonin and dopamine, two neurotransmitters that regulate mood. These chemicals not only influence digestion but can also travel to the brain, where they help improve mood and well-being.
Could Citrus Work Like Antidepressants?
While traditional antidepressant medications, such as selective serotonin reuptake inhibitors (SSRIs), are used to treat depression after it develops, eating citrus may help prevent depression before it starts.
However, it’s difficult to compare their effectiveness directly, and more clinical trials are needed to confirm whether citrus could be a practical treatment option.
Surprising Findings and Future Research
Mehta admitted he was both surprised and not surprised by the results. While there is growing evidence linking gut health to mental health, he had not previously considered oranges as “brain food”. Similarly, while F. prausnitzii is known to have anti-inflammatory benefits, its role in mental health was unexpected.
Looking ahead, the researchers hope to conduct clinical trials to test whether citrus consumption can actively prevent depression or help manage symptoms in people already struggling with the condition. Given the high demand for effective depression treatments, a natural, low-risk option like citrus could be a valuable addition to mental health care.
The Bigger Picture: Diet and Mental Health
This study adds to growing evidence that what we eat affects how we feel. While many people turn to comfort foods for a quick mood boost, researchers are just beginning to understand how diet influences mental health in the long run.
The findings suggest that something as simple as eating an orange daily might help support mental well-being—an easy, natural step toward better mental health.
The research findings can be found in Microbiome.
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