Plain language summary
Depression is a common brain disorder, which may be negatively affected by poor dietary intake. Naturally occurring compounds in fruits, vegetables, tea and cocoa called flavonoids, reportedly improve brain function and may help to lower risk of depression. Possible reasons for this are their influence on the gut microbiota, which can influence the brain. This randomised control trial of 40 individuals with depression aimed to determine the influence of flavonoid rich orange juice on the gut microbiome and symptoms of depression over 8 weeks. The results showed a marginal increase in a key blood indicator associated with symptoms of depression in the flavonoid supplemented group. Symptoms of depression were also decreased in the flavonoid treatment group. Interestingly gut microbiota diversity was higher before treatment, but the abundance of key gut microbiota species were influenced by flavonoid treatment. Biomarkers for depression were also associated with the abundance of gut microbiota. It was concluded that the consequences of high microbial diversity in individuals with depression is not fully understood. However, treatment with flavonoids may alter the gut microbiome and improve symptoms of depression. This study could be used by healthcare practitioners to understand the role of the gut microbiota in depression and recommend dietary changes to include high amounts of flavonoids.
Abstract
Depression is not just a general mental health problem but a serious medical illness that can worsen without treatment. The gut microbiome plays a major role in the two-way communication system between the intestines and brain. The current study examined the effects of flavonoids on depression by observing the changes in the gut microbiome and depressive symptoms of young participants consuming flavonoid-rich orange juice. The depressive symptom was assessed using the Center for Epidemiological Studies Depression Scale (CES-D), a psychiatric screening tool used to detect preexisting mental disorders. The study population was randomly divided into two groups: the flavonoid-rich orange juice (FR) and an equicaloric flavonoid-low orange cordial (FL) group. For 8 weeks, participants consumed FR (serving a daily 380 mL, 600 ± 5.4 mg flavonoids) or FL (serving a daily 380 mL, 108 ± 2.6 mg flavonoids). In total, 80 fecal samples from 40 participants (mean age, 21.83 years) were sequenced. Regarding depression, we observed positive correlations between brain-derived neurotrophic factor (BDNF) and the Lachnospiraceae family (Lachnospiraceae_uc and Murimonas) before flavonoid orange juice treatment. Most notably, the abundance of the Lachnospiraceae family (Lachnospiraceae_uc, Eubacterium_g4, Roseburia_uc, Coprococcus_g2_uc, Agathobacter_uc) increased after FR treatment compared to that after FL treatment. We also validated the presence of unclassified Lachnospiraceae through sensitive real-time quantitative polymerase chain reaction using stool samples from participants before and after flavonoid treatment. Our results provide novel interventional evidence that alteration in the microbiome due to flavonoid treatment is related to a potential improvement in depression in young adults.
Methodological quality
Jadad score
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1
Allocation concealment
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No
