- flavonols are a class of antioxidant compounds found in tea, red wine, broccoli, beans, tomatoes, and leeks that possess anti-inflammatory properties.
- Evidence, predominantly from animal studies, suggests that a higher intake of flavonols may protect against Alzheimer’s and dementia.
- A recent longitudinal study found that higher dietary intake of flavonols was associated with a slower rate of age-related decline in general and specific domains of cognitive function..
A recent study published in Neurology shows that a higher intake of flavonols, a class of flavonoids found in fruits, vegetables, tea, and wine, was associated with a slower rate of cognitive decline in older adults.
The study adds to limited but growing data showing an association between dietary flavonol intake and brain health.
“A healthy diet containing various fruits and vegetables is critical to maintaining health, especially brain health. In general, the vitamins and minerals found in these foods are known to be important. But now we understand that it is the complete composition of the food, including bioactive like flavonols, which make these foods beneficial.”
— Dr Thomas Hollandstudy author and professor at the Rush Institute for Health Aging
“As our knowledge of cognitive decline and the Alzheimer’s dementia disease process expands, and we recognize that it is multifactorial, we must prepare as best we can with multiple science-based tools to help prevent progression with a keep an eye on the ultimate goal of prevention,” said Dr. Holland today’s medical news.
flavonoids are a class of compounds produced by plants that possess antioxidant and anti-inflammatory properties. Flavonoids are present in commonly eaten fruits and vegetables, including berries, cherries, leafy greens, tomatoes, onions, apples, citrus fruits, and beans. Beverages such as tea and red wine are also important sources of dietary flavonoids.
Previous studies have shown that a higher dietary intake of flavonoids is associated with a slower rate of cognitive decline It normally occurs with aging as well as due to Alzheimer’s disease. These effects of flavonoids have been attributed to their ability to reduce oxidative stress, decrease inflammation in the brain, and increase brain plasticity.
exist six major subclasses of flavonoidsincluding flavonols, flavan-3-ols, flavanones, flavones, isoflavones, and anthocyanins.
Furthermore, several compounds make up each subclass of flavonoids. For example, examples of flavonols include compounds such as quercetin, kaempferol, isorhamnetin, and myricetin.
Although animal studies suggest a beneficial impact of certain flavonols and their individual constituents on cognition, similar data from human studies is limited.
A recent study used longitudinal data to examine the impact of total dietary flavonol intake on the rate of decline in cognitive function that typically occurs in older adults. The study also evaluated the association between specific flavonol compounds and age-related changes in cognitive function.
The present study included data from 961 participants who resided in Chicago retirement communities and public housing for the elderly and were enrolled in the Project Rush Memory and Aging. The Rush Memory and Aging Project is a longitudinal study that aims to identify factors associated with declines in cognitive and motor function caused by aging and Alzheimer’s disease.
Participants were between the ages of 58 and 100 and did not have a diagnosis of dementia at the time of enrollment. The researchers evaluated the participants annually to assess cognitive function and risk factors associated with cognitive decline.
To assess cognitive function, a trained technician administered a battery of 19 tests spanning five different cognitive domains. These five domains include:
- episodic memory — a form of long-term memory that encompasses memories of events and experiences
- semantic memory: a form of long-term memory that encompasses factual and conceptual knowledge
- working memory: a form of short-term memory that allows information to be retained and manipulated temporarily
- perceptual speed: the ability to process visual information quickly
- Visuospatial ability: ability to perceive spatial relationships and manipulate images mentally.
Based on overall performance on the 19 cognitive tests, the researchers quantified each participant’s global cognitive function.
To assess dietary intake of flavonols and individual flavonol components, the researchers used a standardized questionnaire to estimate the frequency of intake of flavonol-containing foods in the previous year.
The researchers then examined the association between dietary flavonol intake and cognitive function after adjusting for factors associated with cognitive decline, including age, gender, education level, smoking status, physical activity levels, and participation in cognitively stimulating activities.
Analyzes suggested that higher flavonol intake was associated with a slower decline in global cognitive function.
“In our study population, those who ate the highest level of flavonols (an average of 7 servings of dark leafy greens per week) compared to the lowest had a 32% decrease in their rate of cognitive decline.” said Dr. Holland.
Furthermore, a higher intake of the flavonols kaempferol and quercetin, but not of isorhamnetin and myricetin, was associated with a slower decline in global cognitive function.
By examining changes in specific cognitive domains, the researchers found that higher flavonol intake was associated with slower declines in episodic memory, semantic memory, perceptual speed, and working memory, but not visuospatial ability. .
Among the individual flavonol constituents, a higher intake of kaempferol was associated with a slower rate of decline in all five cognitive domains. By contrast, myricetin was not associated with a change in any cognitive ability, but was suggestive for working memory.
Quercetin intake was associated with a more gradual decline in episodic memory and semantic memory, while isorhamnetin intake was correlated with a more gradual decline in episodic memory and suggestive visuospatial memory.
Leafy vegetables are the richest source of kaempferol. Tea, onions, leeks, broccoli, beans, tomatoes, and berries are some of the other main sources of other flavanols.
Dr. Holland noted that this study highlights the importance of eating a healthy diet rich in flavonoids.
In addition to having beneficial effects on brain health, another recent to study reported an association between a higher intake of flavonoids, including flavonols, and a marker of subclinical atherosclerosis. This further highlights the potential protective effects of flavonoids on not only brain health but also cardiovascular health.
One of the strengths of the study was the use of a trained technician to objectively assess cognitive performance. This is in contrast to the subjective assessments used by previous studies examining the association between flavonoids and cognitive function.
Also, Dr. Martin Roota retired Appalachian State University professor, who was not involved in the study, noted:
“This type of study is difficult to perform because of the difficulty in reliably measuring both dietary intake and cognitive function. The authors improved on this by repeated measures of both over time and by using 19 measures of cognitive function across 5 domains.”
“Another problem with this type of study is that people who eat a healthy diet also tend to have other healthy habits. Additionally, foods that are high in flavonols also tend to contain many other healthy components such as vitamins and minerals. The authors did a respectable job of controlling as best they could for these other complicating factors.”
— Dr. Martin Raíz
The study authors acknowledged that their study had some limitations. They noted that the study had an observational design; therefore, these results do not establish a causal effect of flavonol intake on cognitive decline.
“A limitation of the study is its observational study design and therefore the possibility of ‘residual confounding’ by measured and unmeasured factors, meaning that there could be things that participants are doing that could help or hurt their abilities. cognitive impairment/cognitive impairment, which we are not measuring or aware of,” Dr. Holland noted.
In addition, the researchers assessed dietary intake of flavonols using self-reports, which are prone to bias.
Due to their advanced age, study participants may also have experienced more pronounced cognitive decline due to mild cognitive impairment during the study. These symptoms may cause inaccurate recollection of eating habits or may have caused changes in eating habits.
The majority of the participants enrolled in the study were also white, highly educated, and confined to a limited geographic region. As a result, the study findings may not be generalizable to a broader population.
However, Dr. Holland noted that these results were consistent with other studies.
“Although these limitations exist, supportive findings from long-term follow-up studies on flavonoid intake and cognitive impairment appear to diminish this alternative explanation for our findings,” he said.
