People between the ages of 50 and 65 who eat blueberries every day might be able to lower their risk of developing dementia later in life, according to a report newly published in the medical journal Nutrients.
As the researchers state, “Nearly six million older adults live with dementia in the United States. Alzheimer’s disease (AD) accounts for up to 80% of dementia cases, and it is projected that there will be as many as 14 million cases of AD by the year 2050. There is no treatment for dementia, and it is not clear when effective therapy might be developed. But they also noted, “ … preventive approaches and mitigation of risk for cognitive decline represent the optimal means of coping with this public health challenge … Preliminary studies indicate that blueberry supplementation can improve cognitive performance and influence metabolism and brain function and therefore may have a role in early intervention to prevent neurodegeneration.”
The research team, which was led by Robert Krikorian, PhD, director of the Department of Psychiatry and Behavioral Neuroscience at the University of Cincinnati College of Medicine, enlisted 33 subjects between the ages of 50 and 65. This was a younger group than those previously tested with blueberry supplementation because the researchers were interested in whether blueberries could prevent subjective cognitive decline, or SCD, in later life. The participants had all been diagnosed with prediabetes and were considered overweight (body-mass index [BMI, a measure of weight relative to height] 25 and above). In addition, they had all complained of mild memory problems, a possible indication of early dementia. In all, the group was judged to be at greater risk of cognitive decline as they got older.
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All subjects were told to abstain from berry fruit consumption for 14 days before the beginning of the study and also during the 12-week trial period. Excluded foods included all berry fruits, juices, and extracts but not nonberry fruits and vegetables. Blueberries were the one exception. About half of the participants were given a daily envelope of freeze-dried whole blueberry powder that was the equivalent of a half-cup of fresh blueberries. The remainder received an envelope containing a placebo (inactive) powder. The research team asked participants to consume the contents of one packet with either the morning or evening meal and recommended the powder be mixed with water. At the beginning and the end of the trial, the participants were given cognitive tests that evaluated such factors as mental flexibility, memory, and self-control. Other measurements were also taken, such as blood samples, weight, and waist circumference.
Blueberry consumption linked to cognitive improvements
After the 12-week trial, the research team reported that the blueberry group showed improvements in what the researchers termed “executive ability,” which consists of such attributes as “inhibitory control, task switching, lexical access, and rapid word production.” According to Dr. Krikorian, “This was evident as reduced interference of extraneous information during learning and memory.” The subjects in the blueberry group also showed lower fasting insulin levels, which indicates satisfactory insulin production, improved metabolic function, and the ability to burn fat. Finally, the blueberry group showed what’s known as higher mitochondrial uncoupling, a condition linked to greater longevity and reduced oxidative stress, although the difference was small.
Why might blueberries have these favorable effects? Dr. Krikorian explained that they are high in anthocyanins, which are water-soluble pigments that give certain plants their color (such as the blue in blueberries). Anthocyanins are known to have antioxidant effects, and studies have suggested they are helpful in reducing inflammation, boosting the immune system, and combating viruses, although the evidence remains inconclusive. But whatever the source of blueberries’ benefits, the authors said, “ The demonstration of these benefits in middle-aged individuals with insulin resistance and SCD suggests that ongoing blueberry supplementation may contribute to protection against cognitive decline when implemented early in at-risk individuals.”
Want to learn more about maintaining cognitive health with diabetes? Read “Nine Tips to Keep Your Memory With Diabetes,” “Keeping Your Brain Strong With Diabetes” and “Memory Fitness: How to Get It, How to Keep It.”