The analysis suggested that citrus is positively associated with a type of bacteria in the gut vital for the synthesis of the neurotransmitters serotonin and dopamine — two chemicals in the body linked with improved mood.
“We show that citrus intake is prospectively associated with a greater abundance of [the bacteria] Faecalibacterium prausnitzii, which in turn, is associated with a lower risk of depression,” wrote the study author Raaj Mehta, MPH, MD, an instructor in medicine at Harvard Medical School and a physician at Massachusetts General Hospital in Boston, and his collaborators.
“This finding supports the notion that dietary interventions can mitigate or prevent depression symptoms.”
The Citrus-to-Dopamine Pipeline
Published in the journal Microbiome, the research examined health data from more than 32,000 women who participated in the Nurses’ Health Study and were followed for 14 years.
Researchers determined depression status according to self-reported history of diagnosed depression and regular use of antidepressants. They controlled for several variables, including age, body mass index, exercise, and diet quality.
They found that, compared with participants with the lowest level of citrus consumption, people who ate the most citrus were 22 percent less likely to report depression.
The researchers also looked at depression risk in relation to total fruit and vegetable consumption, and consumption of other individual fruits (specifically apples and bananas). They found no relationship between these foods, food groups, and depression. Only citrus made a difference.
Citrus-Loving Gut Bacteria Tied to Better Mood
Researchers analyzed DNA sequences from participants’ stool samples to look for links between citrus intake and particular species of bacteria in the gut microbiome.
They discovered that one type of bacteria in particular, F. prausnitzii, was more abundant in people who were not depressed than people who were, and that high consumption of citrus was connected with high levels of F. prausnitzii.
To confirm if these findings were similar in men, the study authors turned to data collected from a group of more than 300 men who participated in the Men’s Lifestyle Validation Study. Here, too, they noted that higher levels of F. prausnitzii were tied to lower depression risk scores.
Other Foods Linked to Reduced Depression Symptoms
“What I like about this study is that it provides one simple daily habit that can influence such a serious and widespread condition,” says Lindsay Malone, RDN, an instructor in the department of nutrition at Case Western Reserve’s School of Medicine in Cleveland, who was not involved in the research. “What’s more, there are more benefits to eating oranges than those highlighted in the study, including fiber for digestive health and supporting the gut microbiome, and vitamin C for the immune system.”
Malone stresses that the study shows an association, which doesn’t necessarily mean there is a direct causal relationship between eating citrus fruits and better emotional health. The study participants were mostly middle-aged white women, and citrus may not have the same effect in other groups.
“Wild fatty fish is high in omega-3 fatty acids that can calm inflammation in the brain and body,” says Malone. “Leafy greens and fresh herbs are high in micronutrients and phytonutrients that can influence both the gut microbiome and the nervous system.”
Malone adds that the study doesn’t fully account for other lifestyle factors that could help orange eaters with their mental health.
“People who eat oranges may be more likely to consume other healthy foods and perhaps participate in other healthy lifestyle behaviors, like getting enough sleep, exercising, and practicing stress management,” she says. “One orange a day isn’t going to cut it if you aren’t paying attention to the other foods you are eating, sleep, movement, stress management, and relationships.”
