Association between dietary flavonoid intake and risk of frailty among U.S. middle-aged and older individuals: a cross-sectional study

Background: Flavonoids possess anti-inflammatory, antioxidant, and free radical scavenging properties. Nevertheless, evidence regarding the relationship between dietary flavonoid intake and frailty remains sparse. This study aimed to examine the association between dietary flavonoid intake and the risk of frailty in U.S. adults. Methods: We analyzed data from a nationally representative sample of 3582 middle-aged and older adults from the 2007–2008, 2009–2010, and 2017–2018 cycles of the National Health and Nutrition Examination Survey (NHANES). Flavonoid intake was assessed using a 24-hour dietary recall method. Frailty was measured using a 53-item frailty index. Multivariate logistic regression and restricted cubic splines were used to estimate the association between dietary flavonoid intake and frailty risk. Results: After adjustment for potential confounders, individuals in the highest tertile of total flavonoid intake (odds ratio [OR]: 0.63, 95% confidence interval [CI]: 0.48–0.84), flavan-3-ol intake (OR: 0.72, 95% CI: 0.56–0.92), and flavonol intake (OR: 0.69, 95% CI: 0.52–0.91) exhibited a significantly reduced risk of frailty compared to those in the lowest tertile. Restricted cubic spline analysis revealed a non-linear L-shaped relationship between total flavonoid intake and frailty ( P for non-linearity <0.001). Additionally, a non-linear L-shaped dose–response relationship was observed for the risk of frailty with flavan-3-ol intake ( P for non-linearity = 0.005), while a linear dose–response relationship was found with flavonol intake ( P for non-linearity = 0.365). Conclusions: These findings suggest that higher dietary intake of flavonoids, particularly flavan-3-ols and flavonols, was associated with a lower risk of frailty.