New research reveals a potential protective role for citrus fruits in preventing depression. Faecalibacterium prausnitzii, a type of bacteria found in the human intestine, and its metabolic activity, may influence the impact of citrus fruits and their flavonoids on mood.
Samuthpontorn et al. We report that citrus intake and its ingredients are positively associated with changes in abundance of 15 intestinal microbial species, including reduced risk of depression and enrichment Faecalibacterium prausnitzii. Image credit: Hans.
Depression is a widespread and debilitating condition that affects more than 280 million individuals around the world.
The exact cause of depression is unknown, and treatment is often ineffective.
70% of patients with depression are unable to respond to initial antidepressant treatment and experience unbearable side effects of the drug.
Diet may be a promising tool for preventing and managing depression.
Mediterranean diets are associated with a nearly 35% reduction in the risk of depression, and similar diets show a reduction in mood symptoms.
While the specific food groups underlying these findings remain unknown, recent studies have linked citrus fruits, such as oranges and grapefruits, with a reduced risk of depression.
However, the mechanisms explaining the relationship between diet and depression prevention remain unclear.
In a recent study, Dr. Raaj Mehta, a medical instructor at Harvard Medical School and a physician at Massachusetts General Hospital, along with colleagues, analyzed the interactions between citrus consumption, gut microbiome, and risk of depression in over 32,427 participants.
They prospectively examined the long-term effects of citrus intake on depression, the abundance of gut microbial species, and the potential metabolic pathways related to depression.
“I was collaborating with a talented postdoc named Chatpol Samuthpontorn. He came across a paper from 2016 suggesting that citrus fruits could reduce the risk of depression,” explained Dr. Mehta.
“This finding intrigued us, as we had access to extensive datasets that could help us investigate further.”
“One of these datasets was the Nurse Health Study II (NHS2), which began in 1989 to identify risk factors for major chronic diseases in women.”
“We found evidence in this dataset that nurses who consumed higher amounts of citrus fruits had a lower incidence of depression in the future.”
The authors found that consuming one medium orange per day could reduce the risk of developing depression by about 20%.
“When examining total fruit and vegetable consumption, or other individual fruits like apples and bananas, we did not observe a significant relationship with depression risk,” Dr. Mehta noted.
A unique aspect of this study was that a subset of NHS2 participants provided stool samples over a year for researchers to analyze.
“We used DNA sequencing results from these stool samples to identify links between citrus intake and specific bacterial species in the gut microbiota,” said Dr. Mehta.
“One bacterial species, Faecalibacterium prausnitzii, stood out.”
“People who were not depressed had higher levels of this bacterium, and consuming more citrus was also linked to increased levels of Faecalibacterium prausnitzii.”
“This bacterium may play a key role in connecting citrus consumption with good mental health.”
“We also investigated similar studies involving men, as NHS2 only included women, and found an inverse correlation between Faecalibacterium prausnitzii and depression risk scores in this group,” Dr. Mehta added.
“This raises the question: Does Faecalibacterium prausnitzii contribute to positive mood?”
“One possible explanation is that these bacteria use metabolic pathways, such as the S-adenosyl-L-methionine cycle I pathway, to influence the production of neurotransmitters like serotonin and dopamine in the intestine,” Dr. Mehta explained.
“These neurotransmitters not only influence digestion but can also travel to the brain, where they affect mood.”
“We hope our findings encourage further research into the link between diet and mental health,” Dr. Mehta stated.
“People generally understand that food can impact mood, but researchers are just starting to unravel the specifics.”
A paper detailing these findings was published in the journal Microbiome.
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C. Samuthpontorn et al. 2024. F. Prausnitzii Potentially modulates the association between citrus intake and depression. Microbiome 12, 237; doi:10.1186/s40168-024-01961-3
Source: www.sci.news
