Older people with a high intake of the antioxidant flavanol may be less likely to develop Alzheimer’s dementia, compared with those who have a low intake, report researchers.
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A prospective cohort study including more than 900 older individuals found that those who consumed the most flavonol (a type of flavonoid found in tea, fruits, vegetables, and wine) were at about half the risk of developing the condition, compared with those who consumed the least.
Study author Thomas Holland from Rush University Medical Center in Chicago says more research is needed to confirm the results, but that the findings are “promising.”
Eating more fruits and vegetables and drinking more tea could be a fairly inexpensive and easy way for people to help stave off Alzheimer's dementia…With the elderly population increasing worldwide, any decrease in the number of people with this devastating disease, or even delaying it for a few years, could have an enormous benefit on public health."
Flavonoids are a class of polyphenol representing more than 5,000 bioactive compounds that are known to have antioxidant and anti-inflammatory properties, writes the team in the journal Neurology.
Researchers have previously found that flavonoids as a whole are associated with a decreased risk for Alzheimer’s disease, but Holland says no studies have yet investigated the health effects of flavonols in particular: "Technically speaking, we knew little regarding flavonols, specifically, and Alzheimer's dementia," Holland told MedPage Today reporters.
What did the study involve?
As recently reported in the journal Neurology, Holland and team followed 921 individuals, aged an average of 81 years, who did not have dementia at baseline and who completed yearly questionnaires about their diet, education level, physical activity levels and leisure time as part of the Rush Memory and Aging Project. Participants also underwent annual neurological tests to see whether they had developed Alzheimer’s dementia.
Over a follow-up period of approximately 6 years, the team determined that 220 people had developed Alzheimer’s dementia, based on Neurologic and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS‐ADRDA) criteria.
The participants were divided into five groups based on their intake of four flavonols: kaempferol, quercetin, myricetin, and isorhamnetin. Those in the lowest quintile for flavonol intake consumed an average of 5.3 mg per day, compared with 15.3 mg per day among those in the highest quintile.
People in the highest quintile for overall flavonol intake were at a 48% lower risk
After adjustment for factors that could influence Alzheimer’s risk such as genetic predisposition, physical activity level and health conditions such as diabetes and stroke, people in the highest quintile for overall flavonol intake were at a 48% lower risk of developing Alzheimer’s dementia than those in the lowest quintile.
Of 186 people in the top quintile, 28 (15%) developed the condition, compared with 54 of 182 (30%) in the bottom quintile.
When the team analyzed the participants’ intake of the four flavonol subtypes, they found that people with the highest versus lowest intake of either isorhamnetin (found in pears, tomato sauce, olive oil, and wine) or myricetin (found in tea, wine, oranges, tomatoes, and kale) were at a 38% lower risk for developing Alzheimer’s and those with the highest intake of kaempferol (found in tea, beans, spinach, kale, and broccoli) were at a 51% lower risk.
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.”
The team acknowledges several limitations to the study, including potential residual confounding, an observational design and participants’ self-reporting of food intake.
Holland also notes that the study was not designed to prove cause and effect and only points to an association between flavonol intake and the risk for Alzheimer's dementia.
However, in communications with The Jerusalem Post, Holland advised people to eat fruits and vegetables, particularly dark leafy greens, and to drink some tea now and again:
“A healthy diet that contains various fruits and vegetables is critical for continued health, especially brain health,” he concluded.
TreeHugger. (2020). 11 foods linked to lower risk of Alzheimer's dementia. [online] Available at: https://www.treehugger.com/health/11-foods-and-drinks-linked-lower-risk-alzheimers-dementia.html [Accessed 30 Jan. 2020].
dementia, A. (2020). Study: Antioxidant flavonol linked to lower risk of Alzheimer's dementia. [online] Medicalxpress.com. Available at: https://medicalxpress.com/news/2020-01-antioxidant-flavonol-linked-alzheimer-dementia.html [Accessed 30 Jan. 2020].
The Jerusalem Post | JPost.com. (2020). Fruits, vegetables, tea consumption linked with lower Alzheimer's risk. [online] Available at: https://www.jpost.com/HEALTH-SCIENCE/Fruits-vegetables-tea-consumption-linked-with-lower-Alzheimers-risk-615887 [Accessed 30 Jan. 2020].
Judy George (2020). More Flavonol, Less Alzheimer's. [online] Medpagetoday.com. Available at: https://www.medpagetoday.com/neurology/alzheimersdisease/84603 [Accessed 30 Jan. 2020].