A recent study examined the relationship between citrus intake, gut microbiome composition, and the risk of depression.
The research included 32,427 women from the Nurses’ Health Study II who were followed from 2003 through 2017. Citrus consumption was assessed using validated food frequency questionnaires. During 222,923 person-years of follow-up, higher citrus consumption was associated with a 22% lower risk of incident depression (hazard ratio [HR], 0.78; 95% CI, 0.66–0.90; P for trend = .001) after multivariable adjustment.
Published in Microbiome, the study identified 15 gut microbial species associated with citrus intake, including both positive and negative associations. Faecalibacterium prausnitzii was enriched among participants with higher citrus intake and was inversely associated with depression. Participants with depression had a lower abundance of F. prausnitzii and a reduced presence of the microbial metabolic pathway S-adenosyl-L-methionine (SAM) cycle I. This pathway was negatively associated with depression status (β = –0.005; false discovery rate [FDR] q = 0.01). The authors reported that greater microbial expression of the SAM cycle I pathway was associated with lower expression of monoamine oxidase A in the colon, a gene involved in neurotransmitter degradation.
“The data underscore the role of diet in the prevention of depression and offer a plausible explanation for how the intestinal microbiome modulates the influence of citrus on mental health,” said Chatpol Samuthpongtorn, PhD, of Massachusetts General Hospital and Harvard Medical School.
The researchers also analyzed fecal metagenomics and plasma metabolomics from a nested substudy of 207 women (the Mind Body Study) and validated their findings in a cohort of 307 men from the Men’s Lifestyle Validation Study. In both cohorts, a greater abundance of F. prausnitzii was associated with higher levels of a composite biomarker score based on serotonin and gamma-aminobutyric acid (GABA), which was previously linked to depression.
Lagged analyses with a 4-year gap between dietary intake and depression diagnosis confirmed that the association remained significant (HR, 0.80; 95% CI, 0.67–0.95; P for trend = .002). The study did not find significant associations between total fruit or vegetable intake and depression, suggesting a citrus-specific effect. Among citrus-derived micronutrients, naringenin and formononetin were associated with a lower risk of depression, whereas vitamin C was not.
The authors emphasized that the study was observational and cannot establish causality. Additionally, generalizability may be limited due to the study population, which consisted primarily of white, middle-aged women.
The authors reported no competing interests.
