Higher flavonol intake was linked to lower risk of Alzheimer's dementia in a prospective cohort study of older adults. After adjusting for genetic, demographic, and lifestyle factors, people who consumed the highest dietary intake of flavonols were 48% less like to develop Alzheimer's dementia than people with the least intake, reported Thomas Holland, MD, of Rush University in Chicago, and colleagues, in Neurology. "This research lends a further understanding of the contents of the foods we eat," Holland said. "The bioactives in foods -- which from our research would be specifically flavonols found in kale, spinach, tomatoes, tea, olive oil, apples, pears, and over 20 other foods -- have antioxidant and anti-inflammatory properties that have the potential to protect against cellular damage due to oxidative stress and sustained inflammation," he told MedPage Today. Flavonols are a type of flavonoid, a group of phytochemicals found in plant pigments. "Technically speaking, we knew little regarding flavonols, specifically, and Alzheimer's dementia," Holland said. Earlier research has looked at antioxidants and Alzheimer's risk, but no studies have researched whether dietary intake of flavonoid subclasses is associated with Alzheimer's dementia, he added. This work complements other studies that show fruit and vegetables support brain health, observed Robert Friedland, MD, of the University of Louisville, who wasn't involved with the study. "The presence of flavonols in plants has developed through evolution because of their ability to protect the plant against damaging rays from the sun," he told MedPage Today. "In humans, flavonols similarly protect us from free radicals, products of oxidative metabolism. Flavonol intake also may be beneficial through influence on the partner microorganisms we have in the gut, the microbiota." "Fruit and vegetables are good sources of dietary fiber, which is metabolized by the microbiota, producing short chain fatty acids, enhancing colonic health and serving to produce circulating immune cells which protect the brain from the inflammatory components of neurodegenerative diseases," Friedland continued. "A remarkable array of experimental data has now amply demonstrated the importance of the microbiota in age-related brain diseases." Study Details In this study, Holland and colleagues followed 921 people with no dementia at baseline who participated in the Rush Memory and Aging Project, an ongoing community-based, prospective cohort. Over a mean follow-up of 6.1 years, 220 participants developed Alzheimer's dementia. Clinical diagnoses of Alzheimer's and other dementias were based on Neurologic and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS‐ADRDA) criteria. The average age of the sample was 81, and 75% were female. Each year, participants had annual neurologic evaluations and completed a modified version of the Harvard Food Frequency Questionnaire, which asked about the frequency of eating or drinking 144 food items in the previous 12 months. The researchers multiplied intake frequency by each food's bioactive contents, looking at four flavonols -- kaempferol, quercetin, myricetin, and isorhamnetin -- and total flavonol (the sum of the four individual flavonols). The top contributors to individual flavonols in this cohort were: Isorhamnetin: pears, olive oil, wine, and tomato sauce Kaempferol: kale, beans, tea, spinach, and broccoli Quercetin: tomatoes, kale, apples, and tea Myricetin: tea, wine, kale, oranges, and tomatoes Participants were grouped into quintiles based on how much flavonol was in their diet. The lowest quintile consumed 5.3 mg per day on average; the highest had 15.3 mg per day. People with the highest intake of total flavonols had higher levels of education and more participation in physical and cognitive activities. In models adjusted for age, sex, education, APOE ɛ4, and cognitive and physical activity, people in the highest versus lowest quintiles of total flavonol intake had a 48% lower rate of developing Alzheimer's dementia (HR 0.52, 95% CI 0.33–0.84). People in the highest versus lowest quintile of isorhamnetin intake had a 38% reduced rate of incident Alzheimer's dementia. Similarly, highest versus lowest kaempferol intake showed a 51% lower rate, and highest versus lowest myricetin intake was tied to a 38% reduced rate. Quercetin was not associated with Alzheimer's dementia. This research has limitations, including its observational design and possible residual confounding, Holland and co-authors noted. As in all such studies, participants selected their own diets. Food frequency was self-reported and subject to recall bias, and the study findings may not apply to other populations. It's also possible that dietary changes in participants with subclinical Alzheimer's may have biased the results, the team added. Source
