June 17, 2020
Eating fruits and vegetables may lower your risk of developing Alzheimer’s disease. And it may not take much: including in your weekly meals a few servings of berries, an apple, pear or banana or two, and several cups of tea, for example, may be all it takes.
Researchers looked at health and dietary data from 2,801 men and women who were part of the Framingham Heart Study Offspring Cohort, a large and ongoing study that was started in 1971. Participants underwent regular medical exams every five years. They also regularly filled out detailed questionnaires about the foods they ate, including levels of flavonoids, a group of nutrients found in fruits and vegetables.
The study participants were, on average, around 59 years old when the study started. All were free of Alzheimer’s disease or other forms of dementia at the start.
Over an average follow-up period of nearly 20 years, 193 developed Alzheimer’s disease or other forms of dementia.
The researchers found that those with a low intake of flavonoid-rich foods — equal to eating no berries or tea, and one-and-a-half apples a month — were two to four times more likely to develop Alzheimer’s disease than those who ate higher amounts of these foods. A higher intake was equivalent to including in your monthly diet about seven-and-half cups or blueberries or strawberries, eight apples or pears, and 19 cups of tea.
Intake of one type of flavonoid, anthocyanins, abundant in blueberries, strawberries and red wine, had the strongest association with lowered risk. Apples, pears, oranges, bananas and tea also contributed. The findings were published in the American Journal of Clinical Nutrition.
“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,” said Esra Shishtar, the first author of the study and, at the time, a doctoral student at Tufts University. She added: “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.”
Other, shorter-term studies have suggested that a diet high in fruits and vegetables are good for brain health. This study was unique in that it spanned such a long time period, 20 years, and was therefore proportionally more convincing.
Flavonoids are associated with a variety of health benefits, including lower levels of inflammation. Inflammation is increasingly tied to a number of chronic diseases of aging, including heart disease and dementia.
Flavonoids are antioxidants and help the body to fight toxic compounds such as free radicals that cause oxidative stress. They have been linked to damage to brain function as well as to cancer, strokes, heart disease and other ills. Flavonoids are natural substances found in plants and plant-based beverages, like tea and wine. Other good sources of flavonoids include onions, wine and dark chocolate. As always, it is highly preferable to rely on normal food sources rather than supplements, since high doses of any supplement can induce side effects.
“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 Paul Jacques, the senior author and a nutritional epidemiologist at the Jean Mayer USDA Human Nutrition Center on Aging 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.”
Dr. Jacques also noted that the study participants were all 50 or older at the start of the study, and that’s it never too late to make positive changes to your diet. “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.”
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Esra Shishtar, Gail T Rogers, Jeffrey B Blumberg, 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, May 2020