Dietary flavonoids’ neuroprotective actions involve a variety of effects within the brain, including the ability to protect neurons from injury caused by neurotoxins, the ability to suppress neuroinflammation, and the ability to promote memory, learning, and cognitive function.
According to a study published in the online issue of Neurology®, the medical journal of the American Academy of Neurology, people who eat or drink more foods containing antioxidant flavonols, which are found in several fruits and vegetables as well as tea and wine, may have a slower rate of memory decline.
“It’s exciting that our study shows that making specific dietary choices may lead to a slower rate of cognitive decline,” said Rush University Medical Center in Chicago study author Thomas M. Holland, MD, MS. “Eating more fruits and vegetables and drinking more tea is a simple way for people to play an active role in maintaining their brain health.”
Flavonols are a type of flavonoid, which is a group of phytochemicals found in plant pigments that have been shown to have health benefits.
It’s exciting that our study shows that making specific dietary choices may lead to a slower rate of cognitive decline. Eating more fruits and vegetables and drinking more tea is a simple way for people to play an active role in maintaining their brain health.
Thomas M. Holland
The study included 961 people without dementia who were an average of 81 years old. Every year, they completed a questionnaire about how frequently they ate certain foods. They also took annual cognitive and memory tests, which included recalling word lists, remembering numbers, and arranging them in the correct order. They were also asked about their educational level, how much time they spent doing physical activities, and how much time they spent doing mentally stimulating activities like reading and playing games. They were followed for a period of seven years on average.
The participants were divided into five equal groups based on the number of flavonols in their diet. While the average amount of flavonol intake in US adults is about 16 to 20 milligrams (mg) per day, the study population had an average dietary intake of total flavonols of about 10 mg per day. The lowest group consumed about 5 mg per day, while the highest group consumed about 15 mg per day, which is equivalent to about one cup of dark leafy greens.
The researchers used an overall global cognition score that summarized 19 cognitive tests to determine rates of cognitive decline. The average score ranged from 0.5 for people with no thinking problems to 0.2 for people with mild cognitive impairment to -0.5 for people with Alzheimer’s disease.
After adjusting for other factors that could affect the rate of memory decline, such as age, sex, and smoking, researchers found that the cognitive score of people who had the highest intake of flavonols declined at a rate of 0.4 units per decade more slowly than people whose had the lowest intake. Holland noted this is probably due to the inherent antioxidant and anti-inflammatory properties of flavonols.
The study also broke the flavonol class down into four constituents: kaempferol, quercetin, myricetin and isorhamnetin. The top food contributors for each category were: kale, beans, tea, spinach, and broccoli for kaempferol; tomatoes, kale, apples, and tea for quercetin; tea, wine, kale, oranges, and tomatoes for myricetin; and pears, olive oil, wine, and tomato sauce for isorhamnetin.
People who consumed the most kaempferol had a 0.4 unit per decade slower rate of cognitive decline than those who consumed the least. Those who consumed the most quercetin had a 0.2 unit per decade slower rate of cognitive decline than those who consumed the least. People who consumed the most myricetin had a 0.3 unit per decade slower rate of cognitive decline than those who consumed the least. There was no link found between dietary isorhamnetin and global cognition.
Holland pointed out that while the study found a link between higher levels of dietary flavonols and slower cognitive decline, it does not prove that flavonols directly cause slower cognitive decline. Another limitation of the study is that the food frequency questionnaire, while valid, was self-reported, so people may not remember what they eat accurately.
