Blueberry Pilot Study Finds No Statistically Significant Mood Benefit — SkimNews
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- Courtney L. Millar, PhD led a randomized, double-blind pilot study at Hebrew SeniorLife's Hinda and Arthur Marcus Institute for Aging Research examining whether daily blueberry consumption affects mood and the gut microbiome in adults aged 65 and older with mild depressive symptoms.
- 18 participants completed the three-month trial — 10 in the blueberry group (mean age 71) and 8 in the placebo group (mean age 75) — with the blueberry group consuming 48 grams of blueberry powder daily, roughly equivalent to two cups of fresh berries.
- The mood improvement was not statistically significant compared with the placebo group, despite a greater and more consistent reduction in depressive symptoms among blueberry consumers, according to the study published in the Journal of Nutrition, Health and Aging.
- Metagenomic sequencing found no overall change in microbial species abundance, MetaCyc metabolic pathways, or short-chain fatty acid metabolites, but did identify statistically significant within-group shifts in genes for several gut microbial enzymes in the blueberry arm.
- One highlighted enzyme, EC 3.6.3.31 Polyamine Transporting ATPase, is involved in producing gamma-aminobutyric acid (GABA), a neurotransmitter tied to brain signaling — the lead author called fiber and anthocyanins in blueberries potential modifiers of microbiome pathways relevant to depression in older adults.
- Larger follow-up trials will be needed to determine whether the observed microbial enzyme changes translate into meaningful improvements in mood or depressive symptoms, Millar and colleagues concluded.
- Co-authors included researchers from Harvard T.H. Chan School of Public Health, the Broad Institute of MIT and Harvard, the University of Connecticut's Department of Nutritional Sciences, and UMass Chan Medical School's Department of Psychiatry.
Why it matters: With only 18 completers and no statistically significant mood benefit over placebo, the result is a hypothesis-generating signal rather than proof — but the documented shift in gut-enzyme genes linked to GABA production gives researchers a concrete biological mechanism to test in larger, adequately powered trials targeting an age group where depression is both common and undertreated.
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