Pilot Study Tests Blueberry Powder on Depressive Symptoms in Older Adults
Eighteen participants aged 65 and older consumed 48 grams of freeze-dried blueberry powder daily for three months in a pilot study conducted by researchers in Boston and led by a team at Harvard Medical School. nypost.com reported that the trial examined whether the fruit could alleviate depressive symptoms in an older demographic facing higher baseline risks. Depression affects up to one in three older adults, according to data cited by nypost.com, and is frequently linked to conditions like heart disease, cancer, limited mobility, or sleep problems.
Participants Show Similar Mood Boosts from Blueberry and Placebo Powders
Researchers divided the 18 participants into two groups for the three-month intervention. One group consumed approximately two cups’ worth of freeze-dried blueberry powder each day, while the second group received a placebo powder. By the end of the study period, both groups registered improved moods and a reduction in depressive symptoms. ScienceAlert noted that the magnitude of improvement was comparable between the cohorts, with no statistically significant difference detected in standard mental well-being outcomes. However, the study authors observed that participants consuming the blueberry powder experienced “improvements” of stronger magnitude with less variability compared to the placebo group.
Blueberry Supplements Alter Gut Bacteria and Increase Calming Enzyme Production
Molecular nutritionist Courtney Millar from Harvard Medical School explained to ScienceAlert that the primary objective was to determine the effect of blueberry consumption on the gut microbiome, metabolites, and depressive symptoms. Participants consuming the daily fruit supplement exhibited subtle changes in their gut bacteria. Specifically, five bacterial enzymes increased, including polyamine-transporting ATPase. Researchers theorize this enzyme helps boost GABA, a neurotransmitter responsible for calming the nervous system by slowing down brain activity. Previous research indicates that gut microbes influence the production and regulation of mood-related neurotransmitters like serotonin and GABA via the vagus nerve along the gut-brain axis.
Small Pilot Trial Highlights Need for Larger Future Studies
Study authors emphasized that the pilot trial was primarily designed to test intervention feasibility and gather preliminary data to estimate statistical power for a larger trial. The current sample size remained very small and homogenous, consisting mostly of white women. Experts retain varying views on using diet and supplements to target mental health. Gastroenterologist Dr. David Levinthal, director of UPMC’s Neurogastroenterology and Motility Center, told nypost.com that doctors must be incredibly cautious about recommending these interventions because the clinical evidence is still being established. Beyond gut bacteria changes, a separate 2024 study suggests that anthocyanins—the pigments that make berries blue—can inhibit monoamine oxidase (MAO), an enzyme that breaks down important mood-regulating neurotransmitters including serotonin, dopamine, and noradrenaline.