In a double-blind, placebo-controlled trial, 60 adults aged 65-89 with low berry intake consumed freeze-dried blueberry powder (equal to one cup of fresh fruit) or matched placebo daily for three months. Brain glutathione, measured by multiple quantum chemical shift imaging, did not differ between groups. Blueberries did raise cerebral blood flow versus placebo in the anterior cingulate cortex (P=0.03), with within-group gains of about 7% there and in the caudate, and 6% in the putamen; the placebo group showed no changes.
The null glutathione result matters as much as the positive one. It argues against the popular idea that berry polyphenols work by bolstering the brain's antioxidant pool, and fits a vascular mechanism, plausibly improved endothelial function and nitric oxide signaling, which earlier blueberry trials have linked to better vessel dilation. The anterior cingulate supports executive control, so a perfusion gain there is biologically interesting. Still, blood flow is a surrogate. The abstract reports no cognitive benefit, and only the anterior cingulate difference survived the between-group comparison; the caudate and putamen effects rest on within-group changes, a weaker inference. With 60 completers, three months of follow-up, and a single dose, the trial cannot say whether higher perfusion translates into slower decline or lower dementia risk. This is a modest, mechanistically informative step: one cup of blueberries daily is a low-risk habit with plausible vascular upside, but it remains unproven as a cognitive intervention.