Dr Thomas HollandThomas M. Holland, MD
New study data from the community-based Memory and Aging Project (MAP) has suggested that a higher dietary intake of flavonols may be associated with a lower risk of developing Alzheimer disease dementia.

The study, conducted by Thomas M. Holland, MD, of Rush University, and colleagues, is still ongoing. This dataset includes 921 participants, of which 220 developed Alzheimer disease dementia. The dietary intake of several types these phytochemicals was inversely associated with incident Alzheimer dementia.

The hazard ratios (HR) for the fifth vs. first quintiles of intake of flavonols were: total flavonol, 0.52 (95% CI, 0.33–0.84); for kaempferol, 0.49 (95% CI, 0.31–0.77); for myricetin, 0.62 (95% CI, 0.4–0.97); and for isorhamnetin, 0.62 (95% CI, 0.39–0.98). The only type without the association was quercetin (HR, 0.69; 95% CI, 0.43–1.09). The tests for linear trends were also significant for all assessments aside from quercetin (P = .06).

“More research is needed to confirm these results, but these are promising findings,” Holland said in a statement. “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.” 
 
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The mean age of the cohort was 81.2 years (standard deviation [SD], 7.2), with three-quarters (n = 691) being female. Those with the highest intake of total flavonols had higher levels of education and more participation in physical and cognitive activities.

Holland told NeurologyLive that these data add to the understanding of flavanols and their influence on brain health. As well, because the constituents have this association, it allows for the identification of the foods one can consume to ingest flavonols. A healthy diet, in addition to the general benefits, is essential for brain health.

“When we think of foods, we naturally think about the nutrients, vitamins, and minerals, contained in those foods,” Holland explained. “This research lends a further understanding of the contents of the foods we eat. Although very important, it is not just the nutrients in the foods we eat. It is also the bioactives contained in them.”

“It adds further confidence to the fact that the foods we are consuming do matter. Eat your fruits and vegetables, particularly dark leafy greens, and drink some tea every now and again,” he added.

Top food contributors for each category of flavonol were:
  • Isorhamnetin: pears, olive oil, wine, and tomato sauce
  • Kaempferol: kale, beans, tea, spinach, and broccoli
  • Myricetin: tea, wine, kale, oranges, and tomatoes
  • Quercetin: tomatoes, kale, apples, and tea
The mean amount of flavonol intake in adults in the US is estimated at 16 mg to 20 mg per day. In the MAP cohort, the lowest group (n = 182) had an intake of about 5.3 mg per day and the highest group (n = 186) consumed an average of 15.3 mg per day.

Those in the highest group had a 48% lower chance to develop Alzheimer's dementia than those in the lowest group after adjusting for genetic predisposition, demographic, and lifestyle factors. Of those in the high-intake group, 15% (n = 28) developed Alzheimer's dementia, compared to 30% (n = 54) of the lowest group.

On the flavonol subgroups, a high intake of isorhamnetin resulted in a 38 % lower likelihood to develop Alzheimer, with kaempferol a 51% lower likelihood, and with myricetin a 38% lower likelihood.
REFERENCES
1. Holland TM, Agarwal P, Wang Y, et al. Dietary flavonols and risk of Alzheimer dementia. Neurology. 2020;94:1-8. doi:10.1212/WNL.
2. Study: Antioxidant Flavonol Linked to Lower Risk of Alzheimer’s Dementia: Fruits, Vegetables, Tea May Be Helpful [press release]. Minneapolis, MN: American Academy of Neurology; Published January 29, 2020. eurekalert.org/pub_releases/2020-01/aaon-saf012420.php. Accessed January 30, 2020.