Many foods can alter your mood but a groundbreaking study just published in the journal Microbiome suggests that eating citrus fruits regularly can significantly lower your risk of developing depression, thanks to their beneficial effects on the gut microbiome.

Researchers discovered that frequent citrus consumption is linked to a 22% lower risk of depression, providing compelling evidence that diet profoundly influences mental health.

In the past few decades, scientists have increasingly shown that diet plays a crucial role in mental health. It’s not that there’s a depression-proof diet, but healthy diets — rich in fruits, vegetables, and whole grains — tend to reduce rates of depression. But identifying specific foods that combat depression is more challenging.

The new study started when Raaj Mehta, an instructor in medicine at Harvard Medical School and a physician at Massachusetts General Hospital, teamed up with postdoc Chatpol Samuthpongtorn. The two came across a 2016 paper that mentioned the possibility of citrus reducing the risk of depression. The two set their attention to two long-term cohort studies: the Nurses’ Health Study II (NHS2) and the Men’s Lifestyle Validation Study (MLVS). Over nearly 15 years, they closely tracked citrus intake among 32,427 women and more than 300 men, observing who developed clinical depression.

The results were clear: those consuming the highest amount of citrus fruits — such as oranges, lemons, and grapefruits — had significantly lower depression rates.

“We found that eating one medium orange a day may lower the risk of developing depression by about 20 percent. And the effect seems to be specific to citrus,” Mehta tells The Harvard Gazette. The finding didn’t carry over to other fruits. 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.

This protective effect was strong even after accounting for other lifestyle factors like body mass index (BMI), exercise habits, alcohol intake, and overall diet quality, suggesting something uniquely beneficial about citrus fruits.

Why citrus is so helpful against depression

Citrus fruits are extremely popular fruits, but they don’t affect depression directly. Rather, the key mechanism might lie in the gut microbiome — the community of bacteria living in your digestive system, profoundly influencing your health, mood, and brain function.

The researchers didn’t just find a correlation between citrus and depression, they collected stool samples from some participants. They found that frequent citrus eaters had higher levels of beneficial bacteria in their guts, particularly a species called Faecalibacterium prausnitzii, which seems to have an important role in promoting gut health. This microbe is known to fight inflammation and support brain health.

Interestingly, participants with depression had lower levels of F. prausnitzii compared to non-depressed individuals. Researchers validated this finding in a separate group of men, further strengthening the link between citrus consumption, gut health, and depression.

“So then the question became, how is F. prausnitzii making people feel better? One answer, we think, might be that these bacteria use a metabolic pathway known as the S-adenosyl-L-methionine cycle I pathway to influence levels of two neurotransmitters — serotonin and dopamine — produced by human cells in the gut. These neurotransmitters regulate how food passes through the digestive tract, but they can also travel to the brain, where they elevate mood,” added Mehta.

Not the only anti-depression food

Citrus fruits aren’t the only dietary choice that can positively impact your mental health. Other foods have similarly demonstrated mood-enhancing properties:

• Leafy greens: Spinach, kale, and Swiss chard are rich in folate, a nutrient strongly associated with lower rates of depression.
• Berries: Blueberries, strawberries, and raspberries contain antioxidants and flavonoids linked to improved cognitive function and reduced depression risk. In fact, berries seem to have an even stronger impact than citrus.
• Nuts and seeds: Almonds, walnuts, chia, and flax seeds provide essential nutrients and healthy fats that have been associated with improved mental health.

Beyond dietary changes, your overall lifestyle significantly affects depression risk. Multiple studies have shown that regular physical activity can boost mood, reduce anxiety, and even improve gut health. Exercise helps stimulate beneficial bacteria like F. prausnitzii, creating a virtuous cycle that promotes both gut and mental health.

Similarly, adequate sleep is essential. Chronic sleep deprivation can lead to inflammation and disruptions in gut bacteria, raising depression risk. Maintaining social connections and actively managing stress through mindfulness or meditation practices also protect mental health and support a healthy microbiome.

The study was published in the journal Microbiome.