Higher flavonol intake through food sources, mostly fruits and vegetables, may protect against the development of Alzheimer disease, according to study results published in Neurology.
Previous studies have reported an association between high levels of flavonoid intake and lower risk for Alzheimer disease, but the effect of the flavonol subclass in humans is not known. The goal of this study was to explore the association between intake of flavonols with Alzheimer dementia.
The study included participants from the Rush Memory and Aging Project that completed a comprehensive food frequency questionnaire during their annual evaluations. Of 1920 participants, the current analyses included 921 dementia-free subjects at baseline.
Of 921 participants (mean age 81.2 years, 75% women), 220 developed Alzheimer dementia (39.06 cases per 1000 person-years) during a mean follow-up of approximately 6 years. Participants with the highest intake of total flavonols had higher levels of education were more likely to participate in physical and cognitive activities.
Higher flavonol intake through food sources was found to have a protective role against the development of Alzheimer dementia, independently of many diet, lifestyle, and cardiovascular factors. In a model adjusted for age, sex, education, APOE ɛ4, late-life cognitive activity, and physical activity, participants in the highest vs lowest quintiles of total flavonol intake had a 48% lower rate of developing Alzheimer dementia.
Isorhamnetin, kaempferol, and myricetin were the most significant flavonol constituents and were found to be associated with a reduction of 38%, 50%, and 38%, respectively, in the rate of incident of Alzheimer disease, for those in the fifth vs first quintile of intake. The results remained unchanged following adjustment for diabetes, hypertension, myocardial infarction, and stroke.
The estimated effects of energy-adjusted dietary intake of flavonols on incidence Alzheimer dementia showed a hazard ratio (HR) for the fifth vs first quintile of 0.52 (95% CI, 0.33-0.84, P =.006) for total flavonol, 0.50 (95% CI, 0.31-0.79, P =.002) for kaempferol, 0.62 (95% CI, 0.39-0.98, P =.02) for isorhamnetin, and 0.62 (95% CI, 0.4-0.97, P =.03) for myricetin. Quercetin was not associated with Alzheimer dementia (HR, 0.70; 95% CI, 0.44-1.10, P =.06).
When all 4 flavonols (kaempferol, quercetin, myricetin, and isorhamnetin) were modeled simultaneously, only kaempferol had an independent association with Alzheimer disease.
The researchers acknowledged several study limitations, including the observational design, possible unmeasured confounders, as well as potential recall bias secondary to the use of a self-reported food frequency questionnaire.
“Our findings suggest that dietary intake of flavonols may reduce the risk of developing Alzheimer dementia. Confirmation of these findings is warranted through other longitudinal epidemiologic studies and clinical trials,” concluded the researchers.
Holland TM, Agarwal P, Wang Y, et al. Dietary flavonols and risk of Alzheimer dementia [published online ahead of print, 2020 Jan 29]. Neurology. doi: 10.1212/WNL.0000000000008981