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Green Chinese tea with grape fruit, beetroot, blueberries and raspberries full of antioxidant flavonoid goodness.Brian/iStockPhoto / Getty Images

If berries, apples and tea aren’t part of your regular diet, consider adding them to your menu more often. According to scientists from Tufts University in Massachusetts, eating more of these foods plentiful in natural plant compounds called flavonoids can help guard against Alzheimer’s disease.

The good news: If your diet is low in flavonoids, the findings suggest it doesn’t take much to improve your intake to a potentially beneficial level.

Flavonoids are bioactive compounds found in fruits, vegetables, soybeans, flaxseed, dark chocolate, red wine and tea. They’re categorized into seven classes or types, each one having specific health properties.

The latest evidence

The study, published this month in the American Journal of Clinical Nutrition, examined the relationship between long-term flavonoid intake and the risk of dementia. Alzheimer’s disease is the most common form of dementia, making up 60 per cent to 80 per cent of cases.

While a number of studies have looked at links between diet and dementia over the short term, this one followed 2,801 people for two decades. At the study outset, participants were aged 59, on average, and free of dementia.

Flavonoid intake was measured every four years during the 20-year period. During that time, 193 participants developed dementia, 158 cases of which was Alzheimer’s disease.

A high intake of three flavonoid types was associated with a lower risk of dementia: flavonols (in apples, pears, berries, onions, kale, broccoli, tea), anthocyanins (berries, red grapes, red wine) and flavonoid polymers (tea, apples, cocoa, red grapes, berries, red wine).

Compared with a high intake, a low intake of flavonoids in berries was associated with a four-fold greater risk of developing dementia. A low intake of flavonoids from apples and tea was linked with twice the risk.

To arrive at these results, the researchers controlled for a number of risk factors for dementia, including smoking, physical activity, high blood pressure, high cholesterol, diabetes and overall diet quality.

Flavonoids are thought to improve blood flow in the brain and protect brain cells from inflammation and free radial damage. Flavonoids also play a role in removing toxins and other compounds in the brain that can interfere with cognitive function.

Which foods have flavonoids?

Top flavonoid contributors were tea, apples and pears for flavonols; blueberries, strawberries and red wine for anthocyanins; and tea, apples and pears for flavonoid polymers.

Participants in the highest intake category for flavonoids consumed, per day, 14.2 mg of flavonols, 16.4 mg of anthocyanins and 179 mg of flavonoid polymers.

To put these numbers in perspective, a medium red apple has 7 mg of flavonols and an eight-ounce cup of tea has 9.6 mg, while one cup of blueberries has 240 mg of anthocyanins (along with 16 mg of flavonols) and one cup of strawberries contains 41 mg.

A high intake of these three flavonoid types was equivalent to a monthly intake of 7.5 cups of berries, eight apples and pears and 10 cups of tea.

A low intake was equal to a monthly intake of no berries, one-and-a-half apples and no tea. Drinking a cup of tea each day and eating berries a few times a week would be enough to reach the higher flavonoid intake level.

Strengths, limitations

A credit to this study is that flavonoid intake was assessed repeatedly during the 20-year follow-up period. Had flavonoid intake been measured only once, at the beginning of the study, we wouldn’t know if participants’ intake had changed substantially over the 20 years.

The researchers also utilized a robust database that allowed for the capture of total flavonoid intake, rather than only a few types.

Limitations include the study’s observational design, which can’t prove that a higher flavonoid intake prevented dementia. As well, participants were white and of European descent so the findings may not apply to other populations.

Still, this new study adds to growing evidence that flavonoid-rich foods may offer cognitive benefits.

But let’s also not forget other healthy lifestyle choices that help guard against Alzheimer’s disease, including maintaining a healthy weight, being physically active, moderating alcohol intake and not smoking.

Leslie Beck, a Toronto-based private practice dietitian, is director of Food and Nutrition at Medcan.

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