5 things: Consuming flavonols helps with memory 2:31
Eating more flavonols, antioxidants found in many vegetables, fruits, tea and wine, may slow the rate of memory loss, according to a new study.
People in the study who ate the most flavonols had their cognitive scores decline 0.4 units per decade more slowly than those who ate the least flavonols.
The results held even after adjusting for other factors that can affect memory, such as age, gender and smoking, according to the study recently published in Neurology, the medical journal of the American Academy of Neurology.
"It is exciting that our study shows that choosing a specific diet can lead to a slower rate of cognitive decline," said study author Dr. Thomas Holland, an instructor in the Department of Internal Medicine at University of California Medical Center. Rush University of Chicago, in a statement.
"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."
Flavonols are cytoprotective, meaning they protect cells, including neurons, so it's plausible that there's a direct impact on cognition, said Dr. David Katz, a specialist in preventive and lifestyle medicine and nutrition. who did not participate in the study.
Onions contain the highest levels of quercetin, one of the most common flavonols.
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"But they are also a marker for increased intake of fruits and vegetables, which is good for the brain because it's good for all vital organs, and the body as a whole," Katz said in an email.
"They may also be a marker of better diet quality in general, or even more health conscious. People who are more health conscious may do things to preserve their cognition, or perhaps become more aware of health is a byproduct of better cognition.
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A huge family of phytochemicals
Plants contain more than 5,000 flavonoid compounds, which play roles in producing cell growth, combating environmental stress, and attracting insects for pollination.
Flavonols, a type of flavonoid, have been shown in animal and some human studies to reduce inflammation, a major trigger of chronic disease, and are rich sources of antioxidants.
Antioxidants fight free radicals, "very unstable molecules that form naturally when you exercise and when your body turns food into energy," according to the National Center for Complementary and Integrative Health, part of the National Institutes of Health ( NIH).
One of the most common flavonols, quercetin, has shown promise in reducing the occurrence of colorectal and other cancers, according to studies.
Onions contain the highest levels;
the lowest levels are found in broccoli, blueberries, cauliflower, kale, leeks, spinach, and strawberries.
Another common flavonol, kaempferol, appears to inhibit the growth of cancer cells while preserving and protecting normal cells.
Good sources of kaempferol are onions, asparagus, and blackberries, but the richest plant sources are spinach, kale, and other leafy greens, as well as herbs such as chives, dill, and tarragon.
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A third major player is myricetin, which has been studied in rodents for blood sugar control and reduction of tau, a protein that causes the tangles characteristic of Alzheimer's and other types of dementia.
Spinach and strawberries contain high levels of myricetin, but honey, black currants, grapes and other fruits, berries, green vegetables, nuts, and tea are also good sources.
The last group of flavonols, isorhamnetin, may protect against cardiovascular and neurovascular diseases, as well as provide antitumor and anti-inflammatory benefits.
Pears, olive oil, wine, and tomato sauce are good sources of isorhamnetin.
You can find a full list of the flavonoid content of various fruits and vegetables here.
An older population without dementia
In the new study, 961 people with an average age of 81 and no signs of dementia were asked to fill out a questionnaire about their diet every year for seven years.
In addition, the participants underwent annual cognitive and memory tests and were questioned about the time they spent in physical and mental activity.
People were divided into groups based on their daily intake of flavonols.
The lowest intake was about five milligrams a day;
the highest being 15 milligrams a day, which is equivalent to one cup of dark, leafy vegetables, according to the study.
(For comparison, the average intake of flavonols in American adults is about 16 to 20 milligrams per day, depending on the study.)
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The study looked at the impact of the four main flavonols, kaempferol, quercetin, myricetin, and isorhamnetin, on the rate of cognitive decline over seven years.
The greatest impact was found with kaempferol: according to the study, people who ate the highest amounts of kaempferol-containing foods had a 0.4 unit per decade slower rate of cognitive decline compared to those who ate the least.
Myricetin was as follows: People who ate the most myricetin-containing foods had a 0.3 unit per decade slower rate of cognitive decline compared to the lowest consuming group.
People who ate more foods with quercetin had a 0.2 unit per decade slower rate of cognitive decline.
The study concluded that dietary isorhamnetin had no impact.
Despite the apparent positive aspects, studies on the impact of flavonols on human health are inconclusive, especially since many are observational and cannot demonstrate direct cause and effect.
This also applies to the study published in Neurology, according to its authors.
According to the Linus Pauling Institute, which houses the Micronutrient Information Center, an online database of nutrition information, a few randomized controlled trials, the scientific gold standard, have shown benefits associated with flavonols for sugar control. in blood in type 2 diabetes and improve cardiovascular health.
Whether these benefits are long-term is not known, according to the institute, and no clear impact on cancer prevention or cognitive protection has been shown.
"There are other bioactives that may contribute to the observed results," Katz said.
"Additional studies are needed to fully isolate the effects of flavonoids."
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There's also a downside to assuming a health impact without the necessary studies to back it up, said Dr. Christopher Gardner, professor of Research in Medicine and director of Stanford University's Nutrition Studies Research Group.
"Americans can be counted on to want the benefits of plants but not to eat them," he said in an email.
"(What) if people read the headline and rush to buy bottled (extracted) flavonols instead of eating whole plant foods, and it turns out it wasn't just the flavonols, but the whole plants."