More Evidence Flavonols Preserve Memory, Cognition

Consumption of flavonols may preserve memory and cognition over time, new research suggests. Three specific components of flavonols in particular — kaempferol, myricetin, and quercetin — were associated with slower global cognitive decline.

Dr Thomas Holland

“It is never too early, or too late, to start making healthy lifestyle changes, especially when it comes to diet,” lead investigator Thomas Holland, MD, MS, told Medscape Medical News. Holland is assistant professor at the Rush Institute for Aging at Rush University Medical Center, Chicago, Illinois.

“This work adds to the ever-growing body of evidence that what we eat matters. A diet diverse in fruits and vegetables is critical for both cognitive and physical functioning. A robust lifestyle is necessary for one’s continued health and overall well-being, especially their brain health,” said Holland.

The study was published online November 22 Neurology.

Flavonols and Memory

Flavonols are a subclass of flavonoids, a large class of bioactive compounds with anti-inflammatory properties found in onions, kale, lettuce, tomatoes, apples, grapes, and berries as well as in tea and wine.

Previous research has shown that in mice, quercetin reverses histological hallmarks of Alzheimer’s disease (AD) and protects cognitive function, but there is scant evidence on the effect of flavonols on memory in humans.

For the study, researchers gathered data from the Rush Memory and Aging Project (MAP), a cohort of Chicago residents from retirement communities and senior public housing with no known dementia at baseline.

The study included about 960 participants with an average age of 81 who were followed for an average of 7 years. The majority (75%) were female and White (98%). They filled out a questionnaire each year on how often they ate certain foods. They also completed annual cognitive and memory tests including recalling lists of words, remembering numbers, and putting them in the correct order.

Participants also reported their education level, how much time they spent engaging in physical activities, and doing mentally engaging activities such as reading and playing games.

Participants were divided into five groups based on the amount of flavonols they consumed.

While the average amount of flavonol intake in US adults is about 16-20 mg per day, the group with the lowest flavonol intake consumed about 5 mg per day and the group with the highest consumed an average of 15 mg per day, which is equivalent to 1 cup of dark leafy greens.

To determine rates of cognitive decline, researchers used an overall global cognition score summarizing 19 cognitive tests. The average score ranged from 0.5 for those with no cognitive issues to 0.2 for people with mild cognitive impairment to -0.5 for people with AD.

After adjusting for factors that could affect the rate of memory decline, such as age, sex, and smoking, researchers found that the cognitive score of those who had the highest intake of flavonols — equivalent to one serving of leafy greens per day — vs the lowest, had a 32% decrease in their rate of cognitive decline.

Holland noted that as people age, free radicals can cause cellular damage otherwise known as oxidative stress. “When we ingest foods that contain antioxidants like flavonols or vitamin E, those antioxidants act as reducing agents and essentially destroy free radicals and prevent further cellular damage,” he noted.

He added that although inflammation is a natural process that is necessary for multiple immune responses, sustained or over-activation of immune system can cause damage. “Dietary intake of foods that contain nutrients and bioactives with anti-inflammatory properties can potentially prevent the over-activation or continued response of inflammatory cells and thus avoid cellular damage.”

Kale for Cognition

When the investigators broke flavonols into four constituents — kaempferol, quercetin, myricetin, and isorhamnetin — they found that participants with the highest intake of kaempferol, which is found in kale, beans, tea, spinach, and broccoli, had a 32% slower rate of cognitive decline compared with those with the lowest kaempferol intake.

Those with the highest intake of quercetin, which is found in tomatoes, kale, apples, and tea, had a 30% slower rate of cognitive decline compared with those who consumed the least quercetin.

Participants with the highest intake of myricetin, which is found in wine, kale, oranges, and tomatoes had a 31% slower rate of cognitive decline compared with those who consumed the lowest amount. Dietary isorhamnetin was not tied to global cognition.

Study limitations included the potential for bias due to self-reporting of dietary intake by participants as well as the fact that due to their age, MAP participants could be at risk for cognitive impairment or subclinical disease, which could lead to unreliable reports of dietary consumption.

‘Exciting’ Evidence

“It’s exciting to see evidence that something as simple and empowering as encouraging individuals to enjoy more fruits and vegetables, such as spinach, broccoli, and apples, which are rich in various flavanols, and green/black teas, can stave off cognitive decline,” Uma Naidoo, MD, told Medscape Medical News.

Dr Uma Naidoo

Naidoo is the director of nutritional and metabolic psychiatry at Massachusetts General Hospital and author of the book This is Your Brain on Food: An Indispensable Guide to the Surprising Foods that Fight Depression, Anxiety, PTSD, OCD, ADHD, and More.

“When considering specific plant nutrients, we mustn’t miss the forest for the trees — in general, the more whole, unprocessed foods one consumes, maximizing leafy greens, and eating a variety of colorful vegetables and fruit, the more optimized one’s lifestyle is to help support a healthy brain as one ages,” said Naidoo.

Naidoo noted that a diet rich in flavanols adds “powerful antioxidant compounds that reduce inflammation in the brain, as well as B vitamins which support energy and neurotransmitter production, and fiber, which nourishes the gut. As such, I encourage healthcare professionals to recommend plant-predominant, unprocessed diets to their elderly patients,” she added.

The study was funded by the National Institutes of Health, the National Institute of Aging, and the USDA Agricultural Research Service. Holland and Naidoo reported no relevant financial relationships.

Neurology. Published online November 22, 2022. Abstract.

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