A new Harvard University study suggests that people who eat a diet that includes plenty of flavonoids, natural compounds responsible for the vivid colour of plants, have a 20% lower risk of cognitive decline. The study looked at several types of flavonoids and found that flavones, flavanones and anthocyanins may have the most protective effect.
What are flavonoids?
Flavonoids are naturally-occurring compounds found in fruits, vegetables and other plant foods and are considered powerful antioxidants. It is thought that having too few antioxidants may play a role in cognitive decline as you age.
Flavonoids are categorized into six subclasses, each one residing in certain foods and having specific health properties.
The flavonoids most commonly consumed include anthocyanins (berries, red grapes, cherries, red cabbage), flavan-3-ols (green tea, black tea, cocoa), flavonols (onions, kale, broccoli), flavanones (citrus fruit), flavones (peppers, celery, parsley) and isoflavones (soybeans, legumes).
About the study
The study looked at 49,493 women with an average age of 48 and 27,842 men with an average age of 51 at the start of the study. Over 20 years of follow up, people completed questionnaires every four years about how often they ate various foods.
Study participants also evaluated their own cognitive abilities twice during the study, using questions like, "Do you have more trouble than usual remembering recent events?" and "Do you have more trouble than usual remembering a short list of items?" This assessment captures early memory problems when people's memory has worsened enough for them to notice, but not necessarily enough to be detected on a screening test.
Participants whose diets contained the most flavonoids (versus the least) were 20 per cent less likely to self-report cognitive decline.
Flavones, flavanones, anthocyanins most protective
When researchers looked at individual flavonoids, flavones showed the strongest protective effects. A high intake was tied to a 38 per cent lower risk of subjective cognitive decline, the equivalent of being three to four years younger in age.
Flavanones and anthocyanins were also strongly associated with better later-life subjective cognitive function.
The researchers controlled for other risk factors for dementia such as age, education, physical activity, smoking status, alcohol intake, diabetes, high blood pressure and cardiovascular disease.
Flavonoids are potent antioxidants and, as such, are thought to shield brain cells from free radical damage. Flavanones in citrus have also been shown to inhibit the harmful effects of beta-amyloid, sticky proteins that form plaques and destroy brain cells.
Flavonoids may also protect memory by suppressing inflammation in the brain.
The study was observational so it doesn’t prove cause and effect. As well, dietary data was self-reported and could, therefore, be prone to error. Even so, the study’s strong points – its long follow-up period, large sample size and repeated dietary measurements – add to the validity of the findings.
Source: Neurology, July 28, 2021
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