Objective:To prospectively examine the associations between long-term dietary flavonoids and subjective cognitive decline (SCD).Methods:We followed 49,493 women from the Nurses’ Health Study (NHS) (1984-2006) and 27,842 men from the Health Professionals Follow-up Study (HPFS) (1986-2002). Poisson regression was used to evaluate the associations between dietary flavonoids (flavonols, flavones, flavanones, flavan-3-ols, anthocyanins, polymeric flavonoids, and proanthocyanidins) and subsequent SCD. For the NHS, long-term average dietary intake was calculated from seven repeated food frequency questionnaires (SFFQs), and SCD was assessed in 2012 and 2014. For the HPFS, average dietary intake was calculated from five repeated SFFQs, and SCD assessed in 2008 and 2012.Results:Higher intake of total flavonoids was associated with lower odds of SCD after adjusting for age, total energy intake, major non-dietary factors, and specific dietary factors. Comparing the highest versus the lowest quintiles of total flavonoid intake, the pooled multivariable-adjusted odds ratios (ORs) (95% CIs) of 3-unit increments in SCD was 0.81 (0.76, 0.89). In the pooled results, the strongest associations were observed for flavones (OR=0.62 [0.57, 0.68]), flavanones (0.64 [0.58, 0.68)]), and anthocyanins (0.76 [0.72, 0.84]) (p trend <0.0001 for all groups). The dose-response curve was steepest for flavones, followed by anthocyanins. Many flavonoid-rich foods, such as strawberries, oranges, grapefruits, citrus juices, apples/pears, celery, peppers, and bananas, were significantly associated with lower odds of SCD.Conclusion:Our findings support a benefit of higher flavonoid intakes for maintaining cognitive function in US men and women.

Background Diet is one of the modifiable risk factors for cognitive decline. However, studies on dietary protein intake and cognitive decline have remained limited and inconclusive. Objectives In this study, we aimed to investigate the associations between long-term dietary protein intake and subsequent subjective cognitive decline (SCD). Methods We included 49,493 women from the Nurses’ Health Study (NHS) (1984–2006) and 27,842 men from the Health Professionals Follow-up Study (HPFS) (1986–2002). For the NHS, average dietary intake was calculated from 7 repeated semi-quantitative FFQs (SFFQs), and SCD was assessed in 2012 and 2014. For the HPFS, average dietary intake was calculated from 5 repeated SFFQs, and SCD was assessed in 2008 and 2012. Poisson regression was used to examine the associations between dietary protein, amino acids, and various protein food sources with subsequent SCD. Results Higher protein intake compared with total carbohydrates was associated with lower odds of SCD. When substituting 5% energy from protein for the equivalent percentage of energy from total carbohydrates, the pooled multivariable-adjusted ORs (95% CIs) were 0.89 (0.85, 0.94) for total protein, 0.89 (0.84, 0.94) for animal protein, and 0.74 (0.62, 0.88) for plant protein. When substituting 5% of energy from animal protein with plant protein, the OR was 0.84 (95% CI: 0.72, 0.97). For protein food sources, higher intakes of beans/legumes, fish, and lean poultry were significantly associated with lower odds of SCD, but higher intake of hotdogs was associated with higher odds of SCD. Conclusions Higher protein intake was associated with lower odds of SCD when compared isocalorically with carbohydrate. Plant protein sources were also associated with lower odds when compared with animal protein sources. Our findings suggest that adequate protein intake, and choices of protein sources could play a role in the maintenance of cognition and should be studied further.