Blueberries: vessels yes, memory unsettled, frozen unmeasured

Across 14 randomised trials in 632 people, blueberries improved the lining of the blood vessels by 1.11 percent of flow-mediated dilation and left blood pressure exactly where it was, systolic and diastolic both. A larger pooling of 65 trials on anthocyanins found the same thing and put a dose on it, 50 mg a day, which is an amount ordinary food reaches. Memory is where this gets awkward. A 2021 review of eleven berry trials concluded that berries help memory, attention, processing speed and executive function. A 2026 meta-analysis of 14 blueberry trials, reading much of the same literature, found no effect on executive function and none on mood. Neither paper explains the other, and neither one mentions it. Two teams, one body of evidence, opposite answers. Until somebody reconciles them, the honest position on blueberries and the brain is that we do not know.

The numbers, per 100 g

What a real portion looks like

• Some of the anthocyanin doses behind the 50 mg a day figure came from a 2014 database and from manufacturer correspondence rather than from measurement in the trials. — the randomised trials that reported foods rather than anthocyanin quantities (n = not separately counted in the paper) Evidence C source
  Intakes were computed from the USDA Database for the Flavonoid Content of Selected Foods Release 3.1 of May 2014, and where data were still insufficient, from product brochures or by contacting manufacturers

What your body absorbs

• Of the 203 plant compounds found in people after eating berries, one anthocyanin turns up often enough to trace, and even that one predicts intake only three times in four. — participants of ten clinical trials, searched January 2008 to January 2019 (n = 10 trials, 203 phenolic compounds identified) Evidence C source
  Cyanidin-3-glucoside was the compound found most often, in 69.49 percent of plasma and 58.06 percent of urine samples, with a positive predictive value of 74 percent in plasma (P = 0.210) and 61.7 percent in urine (P = 0.402)
• Which anthocyanin a berry carries changes what it does: delphinidin moved arterial stiffness and insulin, cyanidin moved only vessel dilation. — healthy participants of the pooled trials (n = 65 randomised trials in the parent analysis) Evidence A source
  Cyanidin improved chronic flow-mediated dilation by 1.62 percent (95% CI 1.21 to 2.04), delphinidin improved acute FMD by 1.69 percent, chronic FMD by 1.59 percent, pulse wave velocity by -0.33, insulin by -2.32 pmol/L and triglycerides by -0.10 mmol/L

What it does to your health

• Anthocyanin doses low enough to come from ordinary food, from 50 mg a day, moved vessel function in healthy people across 65 trials. — 18 cohorts in 27 publications and 65 randomised trials, all restricted to healthy participants (n = 65 trials and 18 cohorts) Evidence A source
  Chronic anthocyanin intake improved flow-mediated dilation by 1.41 percent (95% CI 0.90 to 1.91) and acute intake by 1.50 percent (1.16 to 1.84), with lipids, blood pressure, glucose and insulin resistance unaffected. GRADE rated the acute FMD evidence strong and the chronic moderate
• People who habitually ate the most anthocyanins had a quarter less cardiovascular disease in cohorts, and stroke was the one outcome that did not move. — 18 cohorts across 27 publications of healthy participants (n = 4 to 10 studies per outcome) Evidence C source
  Highest against lowest habitual intake: 26 percent lower cardiovascular disease incidence, 18 percent lower myocardial infarction, 11 percent lower type 2 diabetes, 9 percent lower cardiovascular mortality, 8 percent lower hypertension risk, with moderate GRADE evidence for cardiovascular disease and myocardial infarction, and no effect on stroke

What people believe that the data does not support

• Blueberries improved the lining of the blood vessels and left blood pressure exactly where it was, across 14 randomised trials. — 632 healthy participants in 14 trials (n = 14 trials, 632 participants) Evidence A source
  Flow-mediated dilation improved by 1.11 percent (95% CI 0.50 to 1.72, I² = 23%), systolic blood pressure fell 0.11 mmHg (95% CI -2.82 to 2.60) and diastolic 0.46 mmHg (95% CI -2.80 to 1.87), both intervals wide around zero
• The oldest blueberry story of all, that it sharpens night vision, was put to the European Commission and refused. — food labelling in the European Union (n = 5 entries naming blueberry, none authorised) Evidence E source
  POL-HC-8226 on night vision and POL-HC-8227 on antioxidant protection both carry the status Non-authorised, and the register holds no authorised blueberry claim of any kind
• Eighteen separate applications tried to get the word antioxidant onto a European label for anthocyanins, and every one of them failed. — food labelling in the European Union (n = 18 entries naming anthocyanins or anthocyanidins, zero authorised) Evidence E source
  All 18 entries carry the status Non-authorised, covering antioxidant protection, blood fat, blood sugar, eye health, stomach health and cardiovascular claims

Who this works differently for

• In people who already have metabolic syndrome, a cup of blueberries eaten with a heavy meal changed the next day of blood sugar and cholesterol. — 45 adults with metabolic syndrome, mean age 63.4 years, 64 percent male, mean BMI 31.4 (n = 45) Evidence B source
  26 g freeze-dried blueberries, equal to one cup or 150 g fresh, taken with a 969 kcal drink, improved 0 to 24 hour glucose (P < 0.001), insulin (P < 0.01), total cholesterol (P = 0.04), HDL and large HDL particles (P < 0.01), while LDL, triglycerides and ApoB did not change

What is still unknown

• Two reviews read the same trials on berries and memory and reached opposite conclusions, four years apart. — older people with normal cognition or mild cognitive impairment, in 11 included trials using frozen blueberry, concentrate, beverage, capsule, extract and powder (n = 11 trials) Evidence B source
  This 2021 review concluded that berry foods benefit brain perfusion, cognitive function, memory, executive function, processing speed and attention, while the 2026 meta-analysis of 14 blueberry trials found no significant effect on executive function (SMD 0.21, 95% CI -0.05 to 0.46) or mood

The bottom line

One cup a day is the dose with a trial under it. In 45 adults with metabolic syndrome, 26 grams of freeze-dried blueberries, which the authors themselves translate as one cup or 150 grams fresh, taken alongside a 969 kcal meal, improved the following 24 hours of glucose, insulin, total cholesterol and HDL. LDL and triglycerides did not move. Buy them frozen if that is what fits your budget, and know what we cannot tell you about that. Frozen fruit keeps 70 percent of its vitamin C in the USDA retention table, and anthocyanins are not in that table at all, so how many survive a freezer is a question nobody has answered. No trial has ever compared fresh blueberries against frozen ones in people either. Which anthocyanin the berry carries turns out to matter. Delphinidin moved arterial stiffness and insulin, cyanidin moved only vessel dilation, and every trial that simply reported blueberries pooled the two together. The 50 mg figure needs one caveat of its own. Some of the doses behind it were never measured in the trials. They were computed from a USDA flavonoid database published in 2014, from product brochures, and by writing to manufacturers. Europe has refused every blueberry claim ever filed, night vision among them, and all 18 filed for anthocyanins, antioxidant protection among those. None of that means the berry does nothing. It means the thing that has been shown, vessel function in healthy people, is not the thing a label wants to say.

Sources

1. blueberries-e-08 · meta-analysis, methods
   When insufficient data were reported to calculate anthocyanin intake, we calculated intakes (mg/d) using product brochures or by contacting product manufacturers for additional anthocyanin data (which were previously not reported in the original publications).
   American Journal of Clinical Nutrition, 2026 · checked 2026-09-21
2. blueberries-e-05 · systematic review of clinical trials
   Of the 203 phenolic compounds identified in human samples, the anthocyanin cyanidin-3-glucoside was the molecule found most frequently in urine (58.06%) and plasma (69.49%).
   Nutrition Reviews, 2020 · checked 2026-09-21
3. blueberries-e-06 · meta-analysis of randomised trials, subgroup analysis
   In the subanalysis, by anthocyanin type, cyanidin improved chronic FMD (1.62%; 1.21%, 2.04%), whereas delphinidin improved acute FMD (1.69%; 1.20%, 2.18%), chronic FMD (1.59%; 1.21%, 2.04%), chronic pulse wave velocity (-0.33; -0.62, -0.05), insulin (-2.32 pmol/L; -4.39, -0.26), and triglycerides (-0.10 mmol/L; -0.17, -0.03).
   American Journal of Clinical Nutrition, 2026 · checked 2026-09-21
4. blueberries-e-02 · meta-analysis of randomised trials and prospective cohorts
   Across 65 RCTs, chronic anthocyanins (≥1 d) improved flow-mediated dilation (FMD) (net change: 1.41%; 95% confidence interval: 0.90%, 1.91%), acute anthocyanins (≤1 d) improved FMD (1.50%; 1.16%, 1.84%), and insulin concentrations (-2.24 pmol/L; -4.22, -0.27).
   American Journal of Clinical Nutrition, 2026 · checked 2026-09-21
5. blueberries-e-07 · meta-analysis of prospective cohort studies
   Across 18 cohorts in 27 publications, highest compared with lowest habitual anthocyanin intake showed a risk reduction of 26% CVD incidence (4 studies), 18% myocardial infarction (MI, 5 studies), 11% type 2 diabetes mellitus (T2DM, 8 studies), 9% CVD mortality (10 studies), and 8% hypertension risk (6 studies).
   American Journal of Clinical Nutrition, 2026 · checked 2026-09-21
6. blueberries-e-01 · meta-analysis of randomised controlled trials
   Results indicated that blueberry intervention significantly improved flow-mediated dilation (FMD) by 1.11% (95% CI: 0.50, 1.72; I² = 23%), suggesting a positive impact on vascular health.
   Nutrition Research, 2026 · checked 2026-09-21
7. blueberries-e-09 · regulatory decision, EU health claims register
   POL-HC-8226 blueberry extracts blueberry can support maintainig of proper night vision Non-authorised
   EU Register on nutrition and health claims, European Commission, знімок 2026-09-21 · checked 2026-09-21
8. blueberries-e-10 · regulatory decision, EU health claims register
   POL-HC-6609 Anthocyanins Contains naturally occurring antioxidants, which may help to protect against the damage caused by free radicals, as part of a healthy lifestyle. Non-authorised
   EU Register on nutrition and health claims, European Commission, знімок 2026-09-21 · checked 2026-09-21
9. blueberries-e-03 · randomised controlled trial
   Blueberries favorably affected postprandial (0-24 h) concentrations of glucose (p < 0.001), insulin (p < 0.01), total cholesterol (p = 0.04), HDL-C, large HDL particles (L-HDL-P) (both p < 0.01), extra-large HDL particles (XL-HDL-P; p = 0.04) and Apo-A1 (p = 0.01), but not LDL-C, TG, or Apo-B.
   Curtis et al., Clinical Nutrition, 2022 · checked 2026-09-21
10. blueberries-e-04 · systematic review, narrative synthesis
    Existing evidence concludes that berry-based supplements and foods have beneficial effects on resting brain perfusion, cognitive function, memory performance, executive functioning, processing speed, and attention indices.
    Scientific Reports, 2022 · checked 2026-09-21