Benefits
Blood vessel dilation (endothelial function)
Flow-mediated dilation measures how well an artery widens. Daily freeze-dried blueberry, equal to about 1 cup of fresh berries, improved it versus placebo in a 12-week trial in healthy adults aged 65 to 80 and a 6-month trial in adults with metabolic syndrome. A pooled analysis of 14 trials in healthy people found an average gain of about 1.1 percentage points.
Blood pressure
Results are inconsistent. Daily wild blueberry powder lowered 24-hour systolic pressure by about 3.6 mmHg in healthy adults aged 65 to 80, and 22 g/day lowered pressure in 48 postmenopausal women with raised blood pressure. A 6-month trial in metabolic syndrome saw no change, and a pooled analysis of 14 trials in healthy people found no average effect.
Memory and executive function in older adults
In healthy adults aged 60 to 80, 3-month trials of freeze-dried blueberry improved some word-list learning and task-switching scores, and a 6-month trial in older adults with cognitive concerns improved processing speed. Many other tests did not change, delayed recall favored placebo in one trial, a 6-month trial in metabolic syndrome found no cognitive effect, and a pooled analysis found no significant effect on executive function.
Memory and attention in children after a blueberry drink
In healthy 7 to 10 year olds, one drink of wild blueberry powder (in one study the equivalent of about 240 g of fresh berries) improved word recall and some attention measures 1 to 6 hours later versus a matched placebo drink. Reading ability did not change. These were small single-dose studies, and one was funded in part by a wild blueberry industry group.
Insulin sensitivity and blood sugar markers
In 32 adults with obesity and insulin resistance, 6 weeks of blueberry smoothies improved insulin sensitivity on a clamp test versus placebo, and in 52 men with type 2 diabetes, 8 weeks of 22 g/day freeze-dried blueberry ended with lower HbA1c than placebo (7.1% vs 7.5%). The longest trial, 6 months in 115 adults with metabolic syndrome, found no change in insulin resistance.
Muscle strength recovery after hard exercise
In a crossover study of 10 women, blueberry smoothies taken before and after damaging leg exercise sped the return of isometric strength compared with a placebo drink. A systematic review of 13 studies of blueberries, cranberries and bilberries found no difference in exercise performance and a recovery benefit in only one study, so this remains weakly supported.
Mechanism of action
Anthocyanin breakdown products in the blood
After blueberry intake, blood and urine levels of phenolic acids made from anthocyanins rise, and in the 6-month trial they rose with dose. In a short-term trial, the timing of improved artery dilation tracked these circulating metabolites, which the authors suggest links these metabolites to the effect.
Less oxidative enzyme activity in white blood cells
In the same short-term trial, the improvements in artery dilation went along with lower activity of NADPH oxidase, an enzyme in white blood cells that produces reactive oxygen species. This is an association measured over hours, not proof of cause.
Nitric oxide signaling, with inconsistent markers
Nitric oxide relaxes artery walls. Blood nitric oxide rose after 8 weeks of blueberry powder in postmenopausal women, but in the 6-month metabolic syndrome trial nitric oxide levels did not change even though artery dilation improved. How blueberry affects the brain is less clear: in older adults, memory gains came without measurable changes in brain blood flow or gut bacteria.
Clinical trials
Double-blind, placebo-controlled parallel trial of freeze-dried wild blueberry powder, a whole food mixed into a drink rather than an extract (Wood et al. 2023, Am J Clin Nutr).
61 healthy adults aged 65 to 80; 26 g/day of freeze-dried wild blueberry powder (302 mg anthocyanins, equal to 178 g of fresh berries) or a matched placebo for 12 weeks.
Flow-mediated dilation rose by 0.86 percentage points and 24-hour systolic blood pressure fell by 3.59 mmHg versus placebo. Immediate word recall and task-switching accuracy also improved. Delayed word recall, however, was better with placebo. Brain blood flow and gut bacteria composition did not change. A 2025 corrigendum corrected the baseline table and, after removing a missed outlier, reported the task-switching result as P = 0.049.
Double-blind, placebo-controlled parallel trial of two daily amounts of freeze-dried highbush blueberry powder, funded by the US Highbush Blueberry Council with USDA oversight (Curtis et al. 2019, Am J Clin Nutr).
115 adults with metabolic syndrome (average age 63, 68% men); 26 g/day of powder (1 cup of fresh berries, 364 mg anthocyanins), a half-cup equivalent, or placebo for 6 months.
The primary outcome, insulin resistance, did not change. The 1-cup dose improved flow-mediated dilation (+1.45 percentage points) and arterial stiffness, and raised HDL cholesterol in people not taking statins. Blood pressure did not change, and the half-cup dose had no effect on any marker. A secondary analysis found no lasting effect on cognition, mood or sleep.
Randomized, double-blind, placebo-controlled trial of freeze-dried blueberry powder, a whole food rather than an extract (Johnson et al. 2015, J Acad Nutr Diet).
48 postmenopausal women with pre- or stage 1 hypertension; 22 g/day of freeze-dried blueberry powder or a control powder for 8 weeks.
In the blueberry group, systolic pressure fell from 138 to 131 mmHg, diastolic from 80 to 75 mmHg, and a measure of arterial stiffness (brachial-ankle pulse wave velocity) also fell, with significant group-by-time interactions; the control group did not change. Blood nitric oxide rose in the blueberry group.
Double-blind, placebo-controlled trial of smoothies containing blueberry bioactives from whole blueberries; one author received research funds from the US Highbush Blueberry Council (Stull et al. 2010, J Nutr).
32 adults with obesity and insulin resistance but without diabetes; a smoothie with 22.5 g of blueberry bioactives or a matched placebo smoothie twice daily for 6 weeks.
Insulin sensitivity measured by a hyperinsulinemic clamp improved more with blueberry (1.7 vs 0.4 mg per kg fat-free mass per minute, P = 0.04), without changes in body fat, energy intake or inflammatory markers. A larger 6-month trial in adults with metabolic syndrome later found no change in insulin resistance.
Double-blind, placebo-controlled trial of daily freeze-dried (lyophilized) wild blueberry powder, with a reference group of unaffected peers (Cheatham et al. 2023, Nutr Neurosci).
86 older adults with cognitive issues on a screening test (44 blueberry, 42 placebo) for 6 months, plus 45 adults without cognitive issues as a reference group.
Speed of processing on a computerised test battery improved with blueberry versus placebo, reaching the level of the reference group, and brain-wave (event-related potential) measures pointed the same way, most clearly in those aged 75 to 80. The abstract reports speed of processing as the main positive result.
Randomized, single-blind, placebo-controlled parallel trial of a wild blueberry drink, a whole food beverage; the powder and part of the funding came from the Wild Blueberry Association of North America (Barfoot et al. 2019, Eur J Nutr).
54 healthy children aged 7 to 10; one 200 ml drink with 253 mg anthocyanins (about 240 g, or 1.5 cups, of fresh berries) or a matched placebo, tested 2 hours later.
The blueberry group recalled more words on short-delay and learning measures and responded faster on some attention trials without losing accuracy. Reading efficiency did not change.
Randomized, double-blind, placebo-controlled trial of two proprietary products, one a purified wild blueberry extract (ThinkBlue); funded by the maker, Naturex, which helped design the study and write the paper (Whyte et al. 2018, Nutrients).
122 independently living adults aged 65 to 80 with self-reported memory complaints; 500 or 1000 mg/day of an enhanced wild blueberry powder or 100 mg/day extract (about 7 mg anthocyanins), each with small added amounts of L-cysteine and glutathione, or placebo for 6 months.
Only the extract arm differed from placebo: better delayed word recognition and a marginal gain on a spatial memory task at 3 months but not at 6 months, and lower systolic blood pressure at both 3 and 6 months. The two powder doses showed no effect. All three doses are tiny compared with the food-amount trials.
Systematic review and meta-analysis of randomized controlled trials of blueberry products in healthy individuals (He et al. 2026, Nutr Res).
14 randomized controlled trials with 632 healthy participants.
Flow-mediated dilation improved by 1.11 percentage points (95% CI 0.50 to 1.72). Systolic and diastolic blood pressure, executive function and mood showed no significant pooled change. The authors note differences in dose, product type, duration and age between trials.