A growing body of research suggests that what you eat plays a key role in preventing dementia.
For example, greater adherence to a Mediterranean diet has been linked to a lower risk of cognitive impairment and Alzheimer’s disease. Diets high in whole plant foods have been shown to offer the strongest protection against dementia in middle-aged and older adults.
Higher consumption of flavonoids, which are bioactive compounds found in fruits, vegetables, and other plant foods, has also been linked to a lower risk of dementia.
Now, a new study, the largest observational study to date, supports the cognitive benefits of a flavonoid-rich diet.
According to the researchers, following a diet high in “flavonoids” provides significant protection against dementia, especially in people with a high genetic risk and those with symptoms of hypertension or depression.
What’s important to know about the study is which flavonoid-rich foods — and how many servings per day — may provide the most benefits.
Flavonoids and brain health
Flavonoids are a family of more than 5,000 plant compounds (phytochemicals). They are subclassified according to their chemical structure, which affects specific health properties.
Flavonoids are thought to protect brain cells by reducing inflammation, preventing free radical damage, improving blood flow to the brain and blocking the damaging effects of beta-amyloid, sticky proteins that destroy brain cells by forming plaques.
Latest research
The research, published online September 18 in the journal JAMA Network Open, investigated the association between daily flavonoid intake and dementia risk among 121,986 male and female participants in the UK Biobank, an ongoing study of more than 500,000 adults in the United Kingdom.
Participants, aged 40 to 70, provided demographic, health, and lifestyle information through questionnaires and oral interviews. Genetic testing was performed to calculate participants’ genetic risk scores for dementia.
Dietary data was collected twice during the study. A unique “flavodicity” score was calculated for each participant by adding their daily intake of key ingredients from each flavonoid subclass: tea (black and green), red wine, apples, strawberries, grapes, oranges, grapefruit, sweet bell peppers, onions, and dark chocolate.
During 9.4 years of follow-up, 882 participants developed dementia.
Overall, when comparing the highest and lowest flavonoid scores, consuming six more servings per day of flavonoid-rich foods was associated with a 28 percent reduced risk of developing dementia in all participants.
The findings also revealed that a high-flavonoid diet protected against dementia in people with a non-modifiable risk factor (genetics) and in people with a modifiable risk factor (depression or hypertension).
When the researchers looked specifically at participants at high genetic risk, they found that consuming an extra six servings of flavonoid-rich foods per day reduced the risk of dementia by 43 percent.
Among those who reported symptoms of depression at the start of the study, eating six more flavonoid-rich foods per day was associated with a 48% lower risk. In participants with hypertension, the risk of dementia was reduced by 30% in those who ate six more flavonoid-rich foods per day.
Tea, berries and red wine drive research findings
The greatest protection was seen in participants who consumed at least two of these each day: five 6.5-ounce glasses of black or green tea, one 6-ounce glass of red wine and half a serving of berries (two to three tablespoons).
Doing so was linked to a 38 percent lower risk of dementia compared to participants who did not meet either of these ideal intakes, defined as the average daily intake of participants who consumed the most of these foods.
This finding was supported by the researchers’ analysis of flavonoid subclasses. The anthocyanins, flavan-3-ols and flavone subclasses showed the strongest protection against dementia, with tea, red wine and berries among the biggest contributors.
Current data on alcohol consumption and dementia risk are unclear. Current Canadian health guidance is to consume no more than two standard drinks per week for minimal or low risk of adverse health outcomes. One standard drink is equivalent to 5 ounces of wine, 12 ounces of 5% beer, or 1.5 ounces of 80-proof spirits.
Finding flavonoids
According to the researchers, the study results “highlight the benefits of consuming a variety of flavonoid-rich foods to reduce the risk of dementia.”
Include a variety of flavonoid subclasses in your regular diet. These include anthocyanins (berries, red grapes, cherries, red cabbage), flavan-3-ols (green tea, black tea, cocoa), flavonols (onions, kale, arugula, broccoli), flavanones (citrus fruits), flavones (bell peppers, celery, parsley), and isoflavones (soybeans, tofu, chickpeas, peanuts).
Leslie Beck, a private practice dietitian based in Toronto, is the director of food and nutrition at Medcan. Follow her at X @LeslieBeckRD