Blueberry Consumption Improves Cognitive Executive Control in Insulin-Resistant Adults

by | Jun 16, 2022 | 2022, Alzheimer's Disease, Brain Health, Cognitive Health, Fruits and Vegetables

Written by Taylor Woosley, Staff Writer. 12-week supplementation with blueberry powder (equivalent to 0.5 c of blueberries) resulted in significant improvement in lexical access and a reduction of recall intrusion errors, with a significant decline in fasting insulin noted at the 12-week mark.

bowl of blueberries50 million people presently live with dementia worldwide and around 65.7 million people are projected to be diagnosed with a dementia-related disorder by 2030 1. The most common form of dementia, Alzheimer’s disease, is a consequence of protein aggregation, oxidative stress, mitochondrial malfunction, and neuroinflammation2. Cognitive impairment is a prevalent symptom of neurodegenerative diseases and results in loss of learning and memory thinking and may even lead to motor impairment 3. Although there is no current treatment to reverse the effects of dementia, a shift is being made to predict and correct the neural changes that occur up to 2 decades before the onset of dementia through early detection and treatment 4.

Diet may be one way to reduce the risk of dementia. In particular, blueberries display a variety of health-related properties due to their low caloric value paired with dietary fibers and polyphenolic metabolites 5. The flavonoid and polyphenolic phytochemicals found in blueberries have been studied for their anti-oxidative, anti-inflammatory, and immune regulatory activities 6. Polyphenols have important implications for maintaining cognitive functioning across the lifespan 7. Additionally, blueberries contain anthocyanins which are known for their free radical scavenging properties and have been proven to cross the blood-brain barrier with the ability to inhibit reactive oxygen species generation and neuroinflammation in the brain 8.

Krikorian et al. conducted a randomized, double-blind, placebo-controlled trial to assess the effect of blueberry supplementation on cognitive abilities in overweight, non-diabetic, middle-aged adults with subjective cognitive decline. Evaluations such as neuropsychological and mood measures, blood samples of metabolic and lipid markers, and anthropometric indices were performed before and immediately after the 12-week intervention. Participants completed a 3-day diet recording for the week prior to enrollment and during the week prior to the final study to observe possible changes in anthocyanin intake. Additional measures of peripheral platelet mitochondrial function were performed as exploratory markers to assess bioenergetic changes associated with blueberry supplementation.

Subjects (n=27) were randomly assigned to either daily blueberry powder that was equivalent to 0.5 cup of blueberries (BB) (n=13) or placebo powder (PL) (n=14) supplementation. Participants partook in neuropsychological assessments which included measures of executive abilities and long-term memory, along with controlled oral word production testing. Additionally, the California Verbal Learning Test was conducted to observe learning and long-term memory function. The Everyday Memory Questionnaire (EMQ) was included in the study and allowed participants to self-report memory problems in their everyday activities. The Beck Depression Inventory II was used to quantify the amount and severity of depressive symptoms. Analysis of covariance (ANCOVA) tests were performed for each cognitive domain and for metabolic measures. Cohen’s ƒ statistic was used to determine effect size estimates for significant effects and trends. After 12-weeks of intervention, the significant findings are as follows:

  • Compared to placebo, the BB supplementation group had improved lexical access abilities. The effect was robust F (1,24) = 10.67, p = 0.003, with a large effect size, Cohen’s ƒ = 0.66.
  • A statistically significant reduction of recall intrusion errors was observed for the BB supplementation group, F (1,24) = 4.69, p = 0.04, Cohen’s ƒ = 0.20.
  • Analysis of between group effects for EMQ total score resulted in a trend indicating fewer memory complaints overall for the BB supplementation group, EMQ total score, p = 0.10.
  • A significant decline in fasting insulin was noted in the BB supplementation group at week 12, F (1,24) = 4.62, p = 0.04, Cohen’s ƒ = 0.45.
  • A modest trend was noted in the BB supplementation group which suggested enhanced mitochondrial uncoupling (74.1 vs. 83.8), F (1,14) = 2.17, p = 0.11.

Study results show the positive association between blueberry powder consumption and improved lexical access task performance and executive control. Furthermore, 12-week BB supplementation was associated with a decline in fasting insulin. A limitation of the study is the small sample size used. Future research should continue to explore the use of blueberries to combat cognitive impairment in larger study samples.

Source: Krikorian, Robert, Matthew R. Skelton, Suzanne S. Summer, Marcelle D. Shidler, and Patrick G. Sullivan. “Blueberry Supplementation in Midlife for Dementia Risk Reduction.” Nutrients 14, no. 8 (2022): 1619.

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

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Posted June 16, 2022.

Taylor Woosley studied biology at Purdue University before becoming a 2016 graduate of Columbia College Chicago with a major in Writing. She currently resides in Glen Ellyn, IL.

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