Exploring the Impact of Flavonoids on Symptoms of Depression: A Systematic Review and Meta-Analysis
What this study found
Flavonoids significantly reduce depressive symptoms in adults with depressive symptoms across diverse health conditions. Pooled results from 36 clinical trials (n=2,788) show a mean difference in depression scores of −1.65 (95% CI −2.54 to −0.77; p<0.01). Sensitivity analysis removing outliers yielded a still-significant reduction (−0.69; 95% CI −1.13 to −0.25; p<0.01) with heterogeneity reduced (I2 from 92% to 35%). Subgroups with significant effects include isoflavones, flavonols, and flavan-3-ols; effects observed in both controlled and uncontrolled trials, and in double-blind studies.…
- Study & population
- 46 studies (1999–2021): 36 clinical trials (31 randomized controlled trials) and 10 observational cohorts.
- Intervention
- Flavonoid supplementation across subclasses (isoflavones, flavonols, flavan-3-ols, flavones, anthocyanins, proanthocyanidins).
- Key limitation
- High heterogeneity (I2 ≈ 92%), varied flavonoid subclasses, doses, durations and sources; many trials small/underpowered; depressive symptoms measured rather than diagnosed MDD; inconsistent blinding and compliance reporting; dietary intake assessment not standardized; possible confounding dietary factors;…
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Open PDFOriginal abstract
Recent evidence suggests that diet modifies key biological factors associated with the development of depression. It has been suggested that this could be due to the high flavonoid content commonly found in many plant foods, beverages and dietary supplements. Our aim was to conduct a systematic review to evaluate the effects of dietary flavonoids on the symptoms of depression. A total of 46 studies met the eligibility criteria. Of these, 36 were intervention trials and 10 were observational studies. A meta-analysis of 36 clinical trials involving a total of 2788 participants was performed. The results showed a statistically significant effect of flavonoids on depressive symptoms (mean difference = −1.65; 95% C.I., −2.54, −0.77; p < 0.01). Five of the 10 observational studies included in the systematic review reported significant results, suggesting that a higher flavonoid intake may improve symptoms of depression. Further studies are urgently required to elucidate whether causal and mechanistic links exist, along with substantiation of functional brain changes associated with flavonoid consumption.