Middle-aged people who eat strawberries daily could reduce their risk of dementia - study

As the weather turns cooler with November (at least it is supposed to now in Israel), strawberry season is upon us. The luscious red berries are not only tasty, but if consumed on a daily basis, they can lower the danger of developing late-life dementia, according to researchers at the University of Cincinnati. 

Emeritus Prof. Robert Krikorian, former head of the division of psychology, psychiatry, and behavioral neuroscience, has just published his research in the journal Nutrients under the title “Early Intervention in Cognitive Aging with Strawberry Supplementation.” Last year, he and his team published research that found adding blueberries to the daily diets of certain middle-aged populations may lower the chances of developing late-life dementia – and now the research on strawberries is an extension of their blueberry research.

Alzheimer’s disease is the most common form of dementia, accounting for up to 80% of cases, and current projections indicate that it will reach epidemic proportions during the next several years. Paralleling the increase in dementia prevalence is an equally disturbing rise in metabolic disturbance reflected in insulin resistance, hyperinsulinemia, obesity, and related conditions associated with late-life dementia, they wrote.

“Both strawberries and blueberries contain antioxidants called anthocyanins that have been offered a variety of berry health benefits such as metabolic and cognitive enhancements,” said Krikorian. “There is epidemiological data suggesting that people who consume strawberries or blueberries regularly have a slower rate of cognitive decline with aging. 

"In addition to containing anthocyanins, strawberries contain additional micronutrients called ellagitannins and ellagic acid that have been associated with health benefits,” he continued. 

About half of all American and Israeli adults develop insulin resistance – commonly referred to as prediabetes – around middle age. This condition, which is still reversible, has been shown to be a factor in chronic diseases. Krikorian said the metabolic and cardiovascular benefits of strawberry consumption were studied before but not in significant studies on its cognitive effects.

“This study assessed whether strawberry consumption might improve cognitive performance and metabolic health in this population and, if so, whether there might be an association between cognitive enhancement and reduced metabolic disturbance,” he said.

A total of 30 overweight patients between 50 and 65 years old with complaints of mild cognitive decline were enrolled in and completed the study. Krikorian said this population has an increased risk for late-life dementia and other common conditions. 

For four months, the participants were asked to abstain from berry fruit consumption of any kind except for a daily packet of supplement powder to be mixed with water and consumed with breakfast. Half of the participants received powders that contained the equivalent of one cup (the standard serving size) of whole strawberries, while the other half received a placebo. 

More strawberries, better memory

The participants were given tests that measured certain cognitive abilities like long-term memory. The researchers also tracked their mood, metabolic data, and the intensity of depressive symptoms over the course of the study. Those in the strawberry powder group had diminished memory interference, which is consistent with an overall improvement in executive ability. 

“Reduced memory interference refers to less confusion of semantically related terms on a word-list learning test,” Krikorian said. “This phenomenon generally is thought to reflect better executive control in terms of resisting intrusion of non-target words during the memory testing.” 

The strawberry-treated participants also had a significant reduction of depressive symptoms, which Krikorian said can be understood as a result of “enhanced executive ability that would provide better emotional control and coping and perhaps better problem-solving.” While more research is needed, he said the strawberry treatment may have improved cognitive function by reducing inflammation in the brain.

“Executive abilities begin to decline in midlife – and excess abdominal fat, as in insulin resistance and obesity, will tend to increase inflammation, including in the brain,” he said.

“So, one might consider that our middle-aged, overweight, prediabetic sample had higher levels of inflammation that contributed to at least mild impairment of executive abilities. Thus, the beneficial effects we observed might be related to moderation of inflammation in the strawberry group.”

Krikorian added that "future research trials should include larger samples of participants and differing dosages of strawberry supplementation.”