A small pilot study suggests that daily consumption of blueberries could influence gut bacteria and potentially affect mood in older adults. Participants who regularly consumed blueberries saw greater and more consistent reductions in depressive symptoms, as well as subtle changes in genes associated with gut microbial enzymes.
However, improvements in depressive symptoms were not statistically significant compared to the placebo group. Although the results do not establish that blueberries can alleviate depression, they offer preliminary clues to a possible link between blueberry consumption, the gut microbiome and mental health.
“The fiber and anthocyanins found in blueberries have the potential to alter the gut microbiome and metabolites relevant to depression in older adults,” said lead author Courtney L. Millar, PhD, assistant research fellow II at Hebrew SeniorLife’s Hinda and Arthur Marcus Institute for Aging Research and assistant professor of medicine at Beth Israel Deaconess Medical Center and Harvard Medical School. “Our goal was to preliminarily determine the effect of blueberry consumption on the gut microbiome, metabolites, and depressive symptoms.”
Testing the effects of daily consumption of blueberries
To study this potential link, researchers recruited adults aged 65 and older who were physically inactive and had mild depressive symptoms. The pilot study used a randomized, double-blind, parallel-arm, placebo-controlled design to evaluate whether blueberry consumption could influence gut microbes and mood.
For three months, participants consumed either 48 grams of blueberry powder (about two cups of fresh berries) or a matching placebo powder every day.
The researchers examined participants’ gut microbiomes using metagenomic sequencing, which allowed them to measure the abundance of different microbial species and genes. They also used liquid chromatography/mass spectrometry to analyze gut-derived fecal short-chain fatty acids, compounds produced by microbial activity. Depressive symptoms were assessed using validated questionnaires administered before and after the three-month intervention.
Blueberries linked to subtle changes in gut microbial activity
A total of 18 participants completed the study. Most were women and the group was predominantly white (placebo group, n = 8; mean age: 75 ± 6; blueberry group, n = 10; mean age: 71 ± 4).
Despite the encouraging trend in depressive symptoms among participants consuming blueberries, researchers found no statistically significant difference in mood improvement between the blueberries and placebo groups.
The gut microbiome results also revealed a mixed picture. The overall abundance of microbial species, MetaCyc metabolic pathways, and short-chain fatty acid metabolites remained unchanged.
However, the researchers identified statistically significant changes within the blueberry group in the abundance of genes associated with several gut microbial enzymes. One of them was the polyamine transport ATPase EC 3.6.3.31, which is involved in the production of gamma-aminobutyric acid (GABA), a neurotransmitter that plays a role in brain signaling.
These results suggest that blueberries could influence specific aspects of gut microbial function, even without producing measurable changes in overall microbiome composition. Larger studies will be needed to determine whether these changes are linked to significant improvements in mood or depressive symptoms.
The study, “A pilot study of daily blueberry consumption modulates intestinal microbiota enzymatic committees in older, sedentary adults with mild depressive symptoms,” was published in the Journal of Nutrition, Health and Aging.
Other contributors included Mohit P. Chopra, MD, of the Deanna and Sidney Wolk Center for Memory Health at Hebrew SeniorLife and the Department of Psychiatry at UMass Chan School of Medicine; Xochitl Morgan, PhD, and Emily A. Green, PhD, of the Department of Biostatistics, Harvard TH Chan School of Public Health; Alex Wolfe of the Hinda and Arthur Marcus Institute for Aging Research at Hebrew SeniorLife; Kerry A. Pierce of the Broad Institute of MIT and Harvard; and Lidan Gao, PhD, and Christopher N. Blesso, PhD, of the Department of Nutritional Sciences at the University of Connecticut.
Additional contributors were Alyssa B. Dufour, PhD, of the Hinda and Arthur Marcus Institute for Aging Research at Hebrew SeniorLife and the Department of Medicine at Beth Israel Deaconess Medical Center and Harvard Medical School; Douglas P. Kiel, MD, MPH, of the Hinda and Arthur Marcus Institute for Aging Research at Hebrew SeniorLife, Harvard Medical School and Beth Israel Deaconess Medical Center; and Lewis A. Lipsitz, MD, of the Hinda and Arthur Marcus Institute for Aging Research at Hebrew SeniorLife and professor of medicine at Harvard Medical School.
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