Dietary flavonoid intake and psychological well-being - A bidirectional relationship

Higher dietary flavonoid intake has been associated with lower risks of mortality and major chronic disease, yet its relationship with psychological well-being (PWB), a key contributor to health and quality of life, remains unclear. This study aimed to investigate bidirectional associations between dietary flavonoid intake and two PWB facets: happiness (positive emotional state) and optimism (generalized expectation of positive outcomes). Specifically, we examined whether (1) overall flavonoid-rich dietary patterns (flavodiet score), (2) intake of specific flavonoid-rich foods, and (3) total flavonoid and subclass intakes were each associated with happiness and optimism over time.

Data were drawn from the Nurses' Health Study to form two analytical samples. Flavonoid intake measured in 1990 (n = 44,659) was examined in relation to sustained happiness (1992-2000) while intake in 2002 (n = 36,723) was analysed in relation to sustained optimism (2004-2012). Secondary analyses assessed whether higher baseline levels of each PWB facet were associated with sustained higher flavonoid intake, over up to 18 years. Associations were assessed using generalized estimating equations, adjusting for potential confounders.

Higher flavodiet scores were associated with a 3-6 % higher likelihood of sustained happiness [RR_Q4vsQ1 (95 % CI): 1.03 (1.02-1.05)] and optimism [RR_Q4vsQ1 (95 % CI): 1.06 (1.01-1.11)]. Specific flavonoid-rich foods (strawberries, apples, oranges, grapefruit, blueberries) were associated with a 3-16 % greater likelihood of sustained PWB, across the two facets. Similarly, total flavonoid and subclass intakes were associated with a 2-18 % greater likelihood of sustained PWB. Women with higher baseline levels of happiness or optimism were also more likely to sustain a higher flavonoid intake.

Consuming ∼3 servings/day of flavonoid-rich foods is associated with sustained PWB, and higher baseline PWB is associated with sustained higher flavonoid intake over up to 18 years. This bidirectional relationship suggests that integrated interventions targeting both diet and well-being may help promote long-term health and reduce chronic disease risk.