A claim you hear on longevity podcasts

Do blueberries improve artery function?

The claim checked: A cup of blueberries a day helps arteries widen Hear it at 21:01

What do the studies say?

Leaning for

Five studies found blueberries improved flow-mediated dilation, a test of how well an artery widens. The gain ran from 0.86% to 1.50% in the daily trials and the pooled analysis. One trial found no clear change in the 24 hours after one serving. Four reviews of berries in general found smaller or less certain effects.

Computed from 10 studies that test this point, each judged by two readers, in full. 3 more studies are waiting for a full read and do not count yet.

The study behind the claim tested something else. See what it tested

What was said on the podcast?

“Now remember the equivalent of about one cup of blueberries a day across multiple different randomized control trials many many that was associated with improving 1 to 1.5 percentage points in that FMD response.”
Rhonda Patrick, FoundMyFitness · Why Blueberries Are More Than Just Antioxidants · 21:01 on YouTube
The study behind the claim The retelling overstates it

What did the study actually test?

On tape: two meta-analyses, about a cup a day, 1 to 1.5 points of FMD. This review pooled 1.50 points, but its trials gave powders, drinks and fresh berries at different doses, many as a single serving, not one cup a day. Effect of blueberry intervention on endothelial function: a systematic review and meta-analysis. Front Physiol, 2024. Systematic review and meta-analysis of randomized controlled trials of blueberries and endothelial function, Adults in 6 FMD trials: healthy adults, people with metabolic syndrome, postmenopausal women and smokers.

What was saidWhat the study did
What was given Differs About one cup of blueberries a day Freeze-dried powder, fresh berries or blueberry drinks at different doses, often a single serving
Compared with Matches Control Placebo or control in randomized trials
What was measured Matches Flow-mediated dilation Flow-mediated dilation (and reactive hyperemia index)
Who took part Matches Adults Healthy adults, people with metabolic syndrome, postmenopausal women, smokers

What it found

“The pooled results showed a statistically significant increase of 1.50% for FMD (95% confidence interval (CI): 0.81, 2.20; I 2 = 87%; Figure 2 ) after blueberry consumption.”

PMID 38887319

How the authors extend it

“Our meta-analysis showed that blueberry consumption can significantly improve endothelial function, as evaluated using FMD and RHI.”

PMID 38887319

This work was supported by the National Key R&D Program of China (2021YFC2701700, 2021YFC2701704); National Natural Science Foundation of China (81971433, 81971428, 82271749, 82201905,82371717); the Fundamental Research Funds for the Central University (SCU2023D006). Two readers agreed on the label, and the paper was read in full.

The point checked Leaning for

In adults, eating blueberries, about one cup a day or the equivalent, improves flow-mediated dilation by about 1 to 1.5 percentage points

Agree 5

controlled trial · 2013 · landmark

“The magnitude of increase was 2.4 ± 0.5% at 1 h, 1.5 ± 0.4% at 2 h, and 1.2 ± 0.6% at 6 h (Figure 2A).”

Intake and time dependence of blueberry flavonoid-induced improvements in vascular function: a randomized, controlled, double-blind, crossover intervention study with mechanistic insights into biological activity. Am J Clin Nutr
Who: Healthy young men (two crossover RCTs; 10 men in the time-course study, 11 different men in the intake-dependence study)
PMID 24004888

controlled trial · 2019 · landmark

“Over 6 mo, 1 cup blueberries/d improved conduit artery endothelial function (assessed by %FMD; effect size of 1.06% compared with placebo) by a magnitude that translates to a 13% reduction in future CV events based on previous meta-analyses ( 34 ).”

Blueberries improve biomarkers of cardiometabolic function in participants with metabolic syndrome-results from a 6-month, double-blind, randomized controlled trial. Am J Clin Nutr
Who: 115 completers (138 randomized) overweight/obese adults aged 50-75 y with metabolic syndrome, predominantly white men, UK
PMID 31136659

controlled trial · 2023 · landmark

“FMD was significantly higher in the WBB group compared to the placebo after 12 weeks by 0.86 % (95% CI 0.56, 1.17, p<0.001) (Figure 2A).”

Wild blueberry (poly)phenols can improve vascular function and cognitive performance in healthy older individuals: a double-blind randomized controlled trial. Am J Clin Nutr
Who: Healthy older males and postmenopausal females aged 65-80 y, BMI 18-35, London UK
PMID 36972800

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controlled trial · 2023

“Though changes in FMD (not corrected for shear stress) were not statistically significant in our study, likely due to inter-individual variability in shear stress, a clinically significant increase of 1.34% was observed in the blueberry group compared to baseline.”

Daily blueberry consumption for 12 weeks improves endothelial function in postmenopausal women with above-normal blood pressure through reductions in oxidative stress: a randomized controlled trial. Food Funct
Who: Postmenopausal women aged 45-65 years with elevated blood pressure or stage 1 hypertension
PMID 36847333

systematic review · 2024 · cited on tape

“The pooled results showed a statistically significant increase of 1.50% for FMD (95% confidence interval (CI): 0.81, 2.20; I 2 = 87%; Figure 2 ) after blueberry consumption.”

Effect of blueberry intervention on endothelial function: a systematic review and meta-analysis. Front Physiol
Who: Adults in blueberry RCTs: healthy adults, older adults, smokers, adults with metabolic syndrome, postmenopausal women with elevated BP (UK, US, Italy)
PMID 38887319

Partly agree 4

pooled analysis · 2017

“FMD increased (SMD: 0.84%, 95% CI: 0.55, 1.12, p = 0.000, Figure 5 ), with significant heterogeneity ( I 2 = 62.5%).”

The Effect of Anthocyanin-Rich Foods or Extracts on Vascular Function in Adults: A Systematic Review and Meta-Analysis of Randomised Controlled Trials. Nutrients
Who: Healthy or diseased adults (>=18 y) in RCTs of anthocyanin-rich foods, extracts or purified anthocyanins (grape, red orange, cranberry, black raspberry, black currant, rhubarb, blueberry, purified anthocyanins etc.)
PMID 28825651

systematic review · 2020

“Regarding the effects observed in medium-long term interventions, no clear favourable effects of”

Role of berries in vascular function: a systematic review of human intervention studies. Nutr Rev
Who: Systematic review of human RCTs of berries (blueberry, cranberry, strawberry, blackcurrant, raspberry, acai) in healthy subjects or people with cardiovascular risk factors
PMID 31365093

pooled analysis · 2018

“FMD was also consistently increased by the treatment with these compounds although it was only statistically significant when the effects were calculated as DM.”

Meta-Analysis of the Effects of Foods and Derived Products Containing Ellagitannins and Anthocyanins on Cardiometabolic Biomarkers: Analysis of Factors Influencing Variability of the Individual Responses. Int J Mol Sci
Who: Adults (healthy, at-risk, diseased) in RCTs of ellagitannin- or anthocyanin-containing foods: berries, red grapes/wine, pomegranate, nuts
PMID 29495642

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pooled analysis · 2021

“Except for one study in smokers, all studies reported an improved FMD.”

Effects of Berry Anthocyanins on Cognitive Performance, Vascular Function and Cardiometabolic Risk Markers: A Systematic Review of Randomized Placebo-Controlled Intervention Studies in Humans. Int J Mol Sci
Who: Humans in randomized placebo-controlled trials of berry anthocyanins (blueberry, blackcurrant, black raspberry, chokeberry, elderberry, bilberry); mostly healthy children and adults, some with MetS, MI, insulin resistance or (pre)hypertension
PMID 34204250

Disagree 1

controlled trial · 2022

“It is noteworthy that at 3 h, our blueberry intervention group had a 0.5%FMD higher response than placebo, but our primary assessment of responses over 0–24 h was not significantly different.”

Blueberry anthocyanin intake attenuates the postprandial cardiometabolic effect of an energy-dense food challenge: Results from a double blind, randomized controlled trial in metabolic syndrome participants. Clin Nutr
Who: Adults aged 50-75 y with metabolic syndrome (BMI >=25), sub-study of a 6-month RCT, UK
PMID 34883305

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