Scientists who conducted the study examined health data and self-reported food information collected over 20 years from more than 77,000 middle-aged men and women.
The statistics included individuals' weekly intake of foods high in flavonoids, such as vegetables, and whether people experienced cognitive changes in their 70s, such as difficulty in:
recalling recent occurrences or a brief list
recalling what you just experienced
the comprehension of information
after being in a group discussion or following a TV show
discovering their way around the streets that they know well
Researchers then calculated participants’ intake of six classes of flavonoids:
flavonols (such as quercetin in onions and kale)
flavones (such as luteolin in green chile peppers and celery)
flavanones (such as naringenin in grapefruit and oranges)
flavan-3-ol monomers (such as catechins in red wine and strawberries)
anthocyanins (such as cyanidin in blackberries and red cabbage)
polymers (such as theaflavins in black tea).
What they discovered
Following a thorough investigation, researchers discovered that a daily flavonoid intake of at least 25 mg is associated with a 19% lower likelihood of having problems with memory and thinking, as opposed to daily consumption of less than 15 mg.
“These findings are fascinating because they demonstrate that consuming foods high in flavonoids may prevent or slow down deterioration in memory and other cognitive processes in old age,” says Walter Willett, a research author and epidemiology and nutrition professor at Harvard's T.H. Chan School of Public Health.
"We found that earlier intake of flavonoid-rich meals tended to increase the protective impact on the brain. The protective effect on the brain seemed to improve if flavonoid-rich foods were consumed earlier. Even those who started increasing their flavonoid intake later in life were given benefits "Dr Tian-Shin Yeh, the study's lead author and a postdoctoral research fellow in the Harvard-Oxford Program in Epidemiology and the department of nutrition at the Harvard T.H. Chan School of Public Health, said, “When people in the first six months of life don't have enough intake of nutrients like iron and folate, it can affect them later in life and potentially contribute to mental health problems, including schizophrenia, in a way that's additive to other factors.”
The study had a narrow focus and just observed and documented information related to participants' diets and memory problems over time, but it did not provide direct evidence that the consumption of flavonoids helped to slow age-related cognitive decline. However, shorter-term studies have also revealed cognitive health advantages linked to flavonoids.
Flavonoid superstars
Certain flavonoids provided protection to the brain in particular:
Flavones were connected to a 38% decrease in the likelihood of cognitive deterioration as indicated by patients.
Flavanones were shown to have a 36% reduced risk for cognitive impairment.
The research discovered that the probability of self-reported cognitive impairment was 24 per cent lower when anthocyanins were included.
The USDA has compiled a list of the best sources of these three kinds of flavonoids.
The fruits and vegetables in the research that were most strongly related with positive cognitive benefits were, in order of strength:
iceberg lettuce
baked/boiled/mashed potatoes
orange juice
raw carrots
apples/pears
grapefruit juice
bananas
oranges
Brussels sprouts
strawberries
cauliflower
raw spinach
yams/sweet potatoes
blueberries
yellow/orange winter squash
beets
onions
apple juice/cider
tea
white wine
grapes/raisins
red wine.
cooked spinach
cooked carrots
peaches/apricots/plums
cantaloupe
tomato juice
apple sauce
green/red/yellow peppers
broccoli
cabbage
tomato sauce
romaine lettuce
tomatoes
grapefruit
celery
flavonols (such as quercetin in onions and kale)
flavones (such as luteolin in green chile peppers and celery)
flavanones (such as naringenin in grapefruit and oranges)
flavan-3-ol monomers (such as catechins in red wine and strawberries)
anthocyanins (such as cyanidin in blackberries and red cabbage)
polymers (such as theaflavins in black tea).
What they discovered
Following a thorough investigation, researchers discovered that a daily flavonoid intake of at least 25 mg is associated with a 19% lower likelihood of having problems with memory and thinking, as opposed to daily consumption of less than 15 mg.
“These findings are fascinating because they demonstrate that consuming foods high in flavonoids may prevent or slow down deterioration in memory and other cognitive processes in old age,” says Walter Willett, a research author and epidemiology and nutrition professor at Harvard's T.H. Chan School of Public Health.
"We found that earlier intake of flavonoid-rich meals tended to increase the protective impact on the brain. The protective effect on the brain seemed to improve if flavonoid-rich foods were consumed earlier. Even those who started increasing their flavonoid intake later in life were given benefits "Dr Tian-Shin Yeh, the study's lead author and a postdoctoral research fellow in the Harvard-Oxford Program in Epidemiology and the department of nutrition at the Harvard T.H. Chan School of Public Health, said, “When people in the first six months of life don't have enough intake of nutrients like iron and folate, it can affect them later in life and potentially contribute to mental health problems, including schizophrenia, in a way that's additive to other factors.”
The study had a narrow focus and just observed and documented information related to participants' diets and memory problems over time, but it did not provide direct evidence that the consumption of flavonoids helped to slow age-related cognitive decline. However, shorter-term studies have also revealed cognitive health advantages linked to flavonoids.
Flavonoid superstars
Certain flavonoids provided protection to the brain in particular:
Flavones were connected to a 38% decrease in the likelihood of cognitive deterioration as indicated by patients.
Flavanones were shown to have a 36% reduced risk for cognitive impairment.
The research discovered that the probability of self-reported cognitive impairment was 24 per cent lower when anthocyanins were included.
The USDA has compiled a list of the best sources of these three kinds of flavonoids.
The fruits and vegetables in the research that were most strongly related with positive cognitive benefits were, in order of strength:
iceberg lettuce
baked/boiled/mashed potatoes
orange juice
raw carrots
apples/pears
grapefruit juice
bananas
oranges
Brussels sprouts
strawberries
cauliflower
raw spinach
yams/sweet potatoes
blueberries
yellow/orange winter squash
beets
onions
apple juice/cider
tea
white wine
grapes/raisins
red wine.
cooked spinach
cooked carrots
peaches/apricots/plums
cantaloupe
tomato juice
apple sauce
green/red/yellow peppers
broccoli
cabbage
tomato sauce
romaine lettuce
tomatoes
grapefruit
celery
What is the attraction of flavonoids?
We do not know for certain why flavonoids may preserve cognition. However, we do know that flavonoids are potent antioxidants that may help combat brain inflammation and amyloid buildup - two hallmarks of Alzheimer's disease.
Antioxidants may also contribute to
maintaining healthy blood vessels (which keeps blood flowing to the brain) and boosting the synthesis of brain-derived neurotrophic factors, which are substances that repair brain cells, improve their connections, encourage new brain cell development, and increase the hippocampus (a part of the brain involved in the storage and retrieval of memories).
Additionally, we know that flavonoids are related to the prevention of inflammation and tumour formation, as well as with the reduction of blood pressure.
Establishing straightforward flavonoid objectives
With so many possible flavonoid advantages, you may be asking what amount of flavonoids to aim for in your diet. Flavonoid intakes in the research varied from low — about 150 milligrams (mg) per day — to high — approximately 620 mg per day.
However, tracking flavonoids is challenging. They vary considerably according to the diet. Half a cup of blueberries, for example, has around 165 mg of anthocyanins; half a cup of peppers contains approximately 5 mg of flavones. Additionally, many fruits and vegetables include a variety of flavonoids, as well as a variety of other phytochemicals.
Therefore, do not panic. Simply consume a varied diet of fruits and vegetables – the sooner you begin, the better. It's a good idea to hit the daily target of five servings of fruits and vegetables. Recent evidence suggests that the most effective combination is two servings of fruits plus three servings of vegetables per day.
Then, while you eat foods like strawberries, blueberries, peppers, celery, apples, bananas, oranges, and grapefruit, keep in mind that they are not only delicious and nutritious but may also be beneficial to your brain.
"It's called 'eating the rainbow,' and it can result in a more nutritious, delectable diet; it's also another reason why we should ensure that everyone has access to fresh fruits and vegetables," says Dr. Deborah Blacker, a study co-author and professor and deputy chair of epidemiology at Harvard T.H. Chan School of Public Health.
