Older adults who consumed small amounts of flavonoid-rich foods, such and berries, apples, and tea, were two to four times more likely to develop Alzheimer’s disease and related dementias over 20 years compared with people whose intake was higher, according to a new study led by scientists at Tufts University.
 
The study evaluated the health outcomes of 2,800 people 50 years or older and examined the long-term relationship between eating foods containing flavonoids and risk of Alzheimer’s disease and related dementias. While many studies have looked at associations between nutrition and dementias over short periods of time, the study published today in the American Journal of Clinical Nutrition looked at exposure over 20 years.
 
Floavonoids are natural substances found in plants, including fruits and vegetables such as pears, apples, berries, onions, dark chocolate, and plant-based beverages like tea and wine. Flavonoids are associated with reduced inflammation, among other various health benefits.
 
Of the six types of flavonoids, which are derived from different assortments of foods, three were taken into account in this study; flavonols, athocyanins, and flavonoid polymers. Low intake of both flavonols and flavonoid polymers was associated with twice the risk of developing Alzheimer’s disease and related dementias, and that risk appeared to be four-fold in those with low intakes of anthocyanins.
 
“Our study gives 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,” Paul Jaques, senior author and nutritional epidemiologist at the USDA Human Nutrition Research Center on Aging at Tufts University, said. “With no effective drugs currently available for the treatment of Alzheimer’s disease, preventing disease through healthy diet is an important consideration.”
 
All six types of flavonoids found in food were examined, and those long term intake levels were compared with Alzheimer’s disease and related dementias later in life. Low intake was defined as the fifteenth percentile or lower within the population sample.
 
For example, low intake was equal to no berries, roughly one-and-a-half apples, and no tea in any given month. A high intake (60^th percentile or higher) was equal to roughly 7.5 cups of blueberries or strawberries per month, 8 apples and pears per month, and 19 cups of tea per month.
 
Researchers believe based on these results that a cup of tea a day, or some berries two to three times per week would be adequate to mitigate the cognitive risk factors associated with low flavonoid intake levels. Additionally, 50 years old is not too late to make positive dietary changes, Jaques 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,” he said.
 
To evaluate the data, the research team used dietary questionnaires, filled out at medical exams approximately every four years by participants in the Framingham Heart Study, a largely Caucasian group of people who have been studied over several generations for risk factors of heart disease.
 
Researchers excluded questionnaires from the years leading up to the dementia diagnosis based on the assumption that, as cognitive status declined, dietary behavior may have changed, and food questionnaires were more likely to be innacurate.
 
At the start of the study, all participants did not have any cognitive issues, and their food frequency questionnaires were validated at baseline. Flavonoid intakes were updated at each exam to represent cumulative average intake across the five exam cycles.
 
Self-reported food data from food frequency questionnaires were considered one of the study’s limitations due to the possibility of errors in recall. Factors such as education level, smoking status, physical activity, BMI, and overall diet quality may have influenced the results, but these factors were accounted for in the statistical analysis.