Consumption of foods with antioxidant flavonols is associated with a slower rate of memory decline, according to a new study. Foods such as some fruits, vegetables, and tea and wine contain antioxidant flavonols. The study was published in the online issue of Neurology, the medical journal of the American Academy of Neurology, on November 22, 2022. Flavonols are a type of flavonoid, a group of phytochemicals found in plant pigments, and offer a wide variety of benefits such as antimicrobial, antioxidant and anti-inflammatory effects. 


In a statement released by the American Academy of Neurology, Thomas M Holland, one of the authors on the paper, said the study shows making specific diet choices may lead to a slower rate of cognitive decline. He added that something as simple as eating more fruits and vegetables and drinking more tea is an easy way for people to take an active role in maintaining their brain health. 


The researchers analysed 961 people with an average age of 81 without dementia, as part of the study. The participants were asked to fill out a questionnaire each year on how often they ate certain foods. 


What were the study participants asked to do?


They were also asked to complete annual cognitive and memory tests including recalling lists of words, remembering numbers and putting them in the correct order, and asked about other factors such as their level of education, how much time they spent doing physical activities and how much time they spent doing mentally engaging activities such as reading and playing games. 


The participants were followed for an average of seven years. 


Based on the amount of flavonol they had in their diet, the participants were divided into five equal groups. The average amount of flavonol intake in adults in the United States is about 16 to 20 milligrams per day. 


The participants had an average intake of about five milligrams per day, with the highest group consuming an average 15 milligrams per day. This is equivalent to about one cup of dark green leafy vegetables. 


The researchers used an overall global cognition score summarising 19 cognitive tests, to determine rates of cognitive decline. According to the study, the average score ranged from 0.5 for people with no thinking problems to 0.2 for people with mild cognitive impairment. For people with Alzheimer's disease, the score was minus 0.5. 


According to the study, for the people who had the highest intake of flavonols, the cognitive score declined at a rate of 0.4 units per decade more slowly compared to people who had the lowest intake.


This was probably due to the inherent antioxidant and anti-inflammatory properties of flavonols, according to Holland.


Top food contributors for different components of flavonols


Flavonols can be divided into four components, namely kaempferol, quercetin, myricetin and isorhamnetin. 


The top food contributors for kaempferol are kale, beans, tea, spinach and broccoli. For quercetin, the top food contributors are tomatoes, kale, apples and tea.


Tea, wine, oranges, kale and tomatoes are the top contributors for myricetin, and pears, olive oil, wine and tomato sauce are the top contributors for isorhamnetin. 


Important findings


According to the study, people who had the highest intake of kaempferol had a 0.4 units per decade slower rate of cognitive decline compared to those in the lowest group, while those with the highest intake of quercetin had a 0.2 units per decade slower rate of cognitive decline compared to those in the lowest group. 


When compared with their respective lowest groups, the people with the highest intake of myricetin had a 0.3 units per decade slower rate of cognitive decline, while dietary isorhamnetin was not linked to global cognition.


While the study shows an association between higher amounts of dietary flavonols and slower cognitive decline, it does not prove that flavonols directly cause a slower rate of cognitive decline, Holland noted.


Since the food frequency questionnaire was self-reported, there are chances that many people may not have accurately remembered what they consumed.