New US research has found that older adults who include plenty of flavonoid-rich foods in their diet, such as berries, apples and tea, may have a lower risk of developing Alzheimer's disease. Carried out by researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging (USDA HNRCA) at Tufts University in Massachusetts, the new study looked at 2,801 participants aged 50 and older to investigate the relationship between eating foods containing flavonoids and the risk of developing Alzheimer's disease and other related dementias over a period of nearly 20 years.
Flavonoids are natural substances found in plants, fruits, and vegetables, such as pears, apples, berries, onions, and plant-based drinks like tea and wine, as well as in dark chocolate. They have previously been linked to a wide variety of health benefits, however previous studies which have looked at the link between nutrition and dementia have usually only looked at diet over a short period of time.
The findings of the new long-term study, published in the American Journal of Clinical Nutrition, showed that participants who had a low intake of three types of flavonoids appeared to have a higher risk of dementia than those with the highest intake. More specifically, those with a low intake of flavonolds (found in apples, pears and tea) or a low intake of flavonoid polymers (in apples, pears and tea) appeared to have twice the risk of developing Alzheimer's disease and related dementias, while a low intake of anthocyanins (found in blueberries, strawberries and red wine) was associated with a four-fold risk of developing Alzheimer's disease and related dementias.
The researchers explain that a low intake was equal to no berries per month, around one-and-a-half apples per month and no tea. A high intake was equal to around 7.5 cups of blueberries or strawberries per month, eight apples and pears per month, and 19 cups of tea per month. “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 Paul Jacques. “With no effective drugs currently available for the treatment of Alzheimer's disease, preventing disease through a healthy diet is an important consideration.”
"Tea, specifically green tea, and berries are good sources of flavonoids," said first author Esra Shishtar. "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," she said.
Jacques also added that even later in life at age 50, which was the age at which the participants' first had their diets analysed, it's still not too late to make positive diet changes. "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.