Researchers recently conducted a study to see how eating wild blueberries affects the brain and blood vessels of older adults (aged 65 to 80 years). They found that the group of older adults who ate wild blueberry powder daily for 12 weeks had healthier blood vessels and performed better on certain cognitive tasks compared to the group that received a placebo. The study was published in the American Journal of Clinical Nutrition.
As people age, they become more susceptible to cardiovascular and neurodegenerative diseases. Cognitive functions also decline faster in individuals over 60 years old. The inner lining of blood vessels (endothelium) doesn’t work as well with age, which is associated with cardiovascular problems.
Researchers have been looking for ways to slow down or prevent these age-related health issues. One group of substances thought to protect the cardiovascular system from decline is polyphenols. Wild blueberries are rich in a specific type of polyphenols called anthocyanins, along with other beneficial compounds like procyanidins, flavanols, and phenolic acids. Previous studies have shown that daily consumption of blueberries has positive effects on thinking skills and memory in older adults after at least 6 weeks of regular intake.
In this study, led by Eleanor Wood, the researchers wanted to investigate how daily consumption of blueberries affects cognitive performance and blood vessel function in healthy older adults. They also wanted to explore potential mechanisms behind these effects, so they measured cerebral blood flow in the brain and examined the diversity and composition of gut microbiota. Gut microbiota refers to billions of microorganisms living in our digestive system, which play a vital role in digestion and various bodily functions.
The study included 61 healthy older adults between 65 and 80 years old, all with good cognitive abilities and no chronic diseases or cognitive impairments.
Participants were randomly divided into two groups. Neither the participants nor the staff knew which group each participant belonged to. One group received sachets containing 26 grams of freeze-dried wild blueberry powder, equivalent to 178 grams of fresh wild blueberries. These sachets contained 302mg of anthocyanins (the beneficial compound found in blueberries). The other group received identical-looking sachets filled with a powder that tasted the same, contained fiber and vitamin C, but had no anthocyanins. This was the placebo treatment, designed so participants couldn’t distinguish it from the real blueberry powder.
Participants were instructed to keep the sachets in the freezer to preserve the polyphenols and consume one sachet with water every day for 12 weeks. Researchers collected empty sachets to verify that participants followed the instructions and consumed the powder as directed.
Before and after the study, researchers measured how much the participants’ blood vessels expanded when blood flow increased (flow-mediated vasodilation) using high-resolution ultrasound. They also assessed cognitive performance using five tasks: Reys Auditory Verbal Learning Task (AVLT), Corsi blocks task, Serial 3s and 7s subtraction tasks, and the Switching task.
Additionally, they measured the stiffness of participants’ arteries, 24-hour blood pressure, blood flow in the brain using non-imaging transcranial Doppler ultrasound, plasma lipids, plasma and urine polyphenol metabolites, mood, and gut microbiota diversity and composition from stool samples. Participants were given a low-fat and low-polyphenol breakfast before cognitive testing and blood flow measurements, and they kept 7-day food diaries to track their usual diets.
Results showed that consuming wild blueberry powder improved vascular function. The ability of blood vessels to expand when blood flow increased (flow-mediated dilation) was much better in the group that consumed the blueberry powder compared to the placebo group. The 24-hour systolic blood pressure was also lower in the blueberry group.
Moreover, the blueberry consumption improved certain aspects of cognition. Participants in the blueberry group showed better immediate word recall and performance in the switching task after the treatment compared to the placebo group. However, the placebo group performed slightly better in delayed memory recall. Other measures taken did not show significant differences.
“We observed that 12 weeks of daily wild blueberry consumption improved flow-mediated dilation [the ability of blood vessels to expand in response to increased blood flow] by 0.85% and ambulatory systolic blood pressure decreased by -3.59 mmHg with respect to the control, while no effects were found in arterial stiffness and blood lipids. This is consistent with our previous study in younger healthy males where a 1.5% increase in flow-mediated dilation and systolic blood pressure decreased by 5.6 mmHg after 4-week consumption of similar amounts of wild blueberries,” the study authors concluded.
The study provides valuable insights into the health effects of consuming polyphenols in older adults. However, it has some limitations. Magnetic resonance imaging would have been a more precise method to measure blood flow in the brain, but the researchers did not have access to this technology. Additionally, the treatment’s effects varied significantly among participants, and the researchers didn’t investigate the reasons behind this variability.
The paper, “Wild Blueberry (Poly)phenols can Improve Vascular Function And Cognitive Performance In Healthy Older Males And Females: A Double-Blind Randomized Controlled Trial“, was authored by Eleanor Wood, Sabine Hein, Robin Mesnage, Filipe Fernandes, Nimaya Abhayaratne, Yifan Xu, Zicheng Zhang, Lynne Bell, Claire Williams, and Ana Rodriguez-Mateos.