Higher long-term dietary intakes of flavonoid-rich foods, such as berries, apples and tea, are associated with lower risks of Alzheimer’s disease and related dementias, according to a new study published in the American Journal of Clinical Nutrition.
Higher long-term dietary intakes of flavonoids are associated with lower risks of Alzheimer’s disease and related dementias in U.S. adults. Image credit: HeVoLi.
Flavonoids are natural substances found in plants, including fruits and vegetables such as pears, apples, berries, onions, and plant-based beverages like tea and wine.
They are associated with various health benefits, including reduced inflammation. Dark chocolate is another source of flavonoids.
“Our study gives us a picture of how diet over time might be related to a person’s cognitive decline, as we were able to look at flavonoid intake over many years prior to participants’ dementia diagnoses,” said senior author Dr. Paul Jacques, a nutritional epidemiologist in the Jean Mayer USDA Human Nutrition Research Center on Aging and the Friedman School of Nutrition Science and Policy at Tufts University.
“With no effective drugs currently available for the treatment of Alzheimer’s disease, preventing disease through a healthy diet is an important consideration.”
The study included 2,800 people (mean baseline age – 59.1 years, 52% females) and examined the long-term relationship between eating flavonoid-rich foods and risks of Alzheimer’s disease and related dementias.
The authors used data from the Framingham Heart Study (FHS), a long-term ongoing cohort study designed to explore cardiovascular disease risk factors in residents of the city of Framingham, Massachusetts.
To measure long-term flavonoid intake, they used dietary questionnaires, filled out at medical exams approximately every four years by FHS participants.
The researchers categorized flavonoids into six types and created four intake levels based on percentiles: less than or equal to the 15th percentile, 15th-30th percentile, 30th-60th percentile, and greater than 60th percentile.
Examples of the levels studied included:
(i) low intake (15th percentile or lower) was equal to no berries (anthocyanins) per month, roughly one-and-a-half apples per month (flavonols), and no tea (flavonoid polymers);
(ii) high intake (60th percentile or higher) was equal to roughly 7.5 cups of blueberries or strawberries (anthocyanins) per month, 8 apples and pears per month (flavonols), and 19 cups of tea per month (flavonoid polymers).
The scientists compared flavonoid intake types and levels with new diagnoses of Alzheimer’s disease and related dementias later in life.
They found that low intake (15th percentile or lower) of three flavonoid types was linked to higher risk of dementia when compared to the highest intake (greater than 60th percentile):
(i) low intake of flavonols (apples, pears and tea) was associated with twice the risk of developing Alzheimer’s disease and related dementias;
(ii) low intake of anthocyanins (blueberries, strawberries, and red wine) was associated with a four-fold risk of developing Alzheimer’s disease and related dementias;
(iii) low intake of flavonoid polymers (apples, pears, and tea) was associated with twice the risk of developing Alzheimer’s disease and related dementias.
“Tea, specifically green tea, and berries are good sources of flavonoids,” said first author Dr. Esra Shishtar, also from the Jean Mayer USDA Human Nutrition Research Center on Aging and the Friedman School of Nutrition Science and Policy at Tufts University.
“When we look at the study results, we see that the people who may benefit the most from consuming more flavonoids are people at the lowest levels of intake, and it doesn’t take much to improve levels.”
“A cup of tea a day or some berries two or three times a week would be adequate.”
“50, the approximate age at which data was first analyzed for participants, is not too late to make positive dietary changes,” Dr. Jacques said.
“The risk of dementia really starts to increase over age 70, and the take home message is, when you are approaching 50 or just beyond, you should start thinking about a healthier diet if you haven’t already.”
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Esra Shishtar et al. Long-term dietary flavonoid intake and risk of Alzheimer disease and related dementias in the Framingham Offspring Cohort. American Journal of Clinical Nutrition, published online April 22, 2020; doi: 10.1093/ajcn/nqaa079
