Blueberries and grapes: half the sugar and a small artery signal

In a meta-analysis of 14 randomized trials with 632 healthy people, eating blueberries raised flow-mediated dilation, a measure of how well arteries widen, by 1.11 percentage points (95% CI 0.50 to 1.72), across trials that differed in dose, form and duration. The same analysis found no significant effect on executive function (SMD 0.21, 95% CI -0.05 to 0.46) or mood. Intervals that wide leave the brain question open. We found no trial that put the two fruits head to head. What separates them clearly is sugar. Per 100 g, raw blueberries measured 9.4 g of fructose plus glucose against 17.3 g in red seedless grapes, over 8 US samples each, and the UK tables agree at 9.1 g against 16.1 g of total sugars. A cup of either is 150 g in the US survey, so a cup of grapes brings nearly twice the sugar of a cup of blueberries. Grapes hold more potassium, 229 mg per 3.5 oz (100 g) against 86 mg.

How much is actually in it

• Per 100 g, raw blueberries measured more than twice the vitamin C of red seedless grapes (8.1 vs 3.3 mg) and about half the sugar (9.4 vs 17.3 g fructose plus glucose), while grapes held more potassium (229 vs 86 mg). — USDA Foundation Foods samples: Blueberries, raw and Grapes, red, seedless, raw (n = 8 samples each) Evidence E source
  Vitamin C 8.06 mg (4.30 to 11.1) vs 3.31 mg (2.18 to 4.91), potassium 85.6 mg (74.2 to 109.5) vs 229.4 mg (169 to 273) per 3.5 oz (100 g)
• The UK food tables give 40 calories and 9.1 g sugars per 3.5 oz (100 g) for blueberries against 65 calories and 16.1 g for grapes, with about ten times more manganese in blueberries. — CoFID records 14-325 Blueberries and 14-350 Grapes, average (n = 2 records) Evidence E source
  Energy 40 vs 65 calories, total sugars 9.1 vs 16.1 g, AOAC fiber 1.5 vs 1.3 g, potassium 66 vs 215 mg, manganese 0.69 vs 0.06 mg per 3.5 oz (100 g)

What a real portion looks like

• US dietary surveys count a cup of either fruit as 150 g and an unspecified serving as 75 g, with one grape weighing about 7 g and one blueberry about 2 g. — FNDDS records Blueberries, raw (63203010) and Grapes, raw (63123000) (n = 2 records) Evidence E source
  1 cup 150 g, quantity not specified 75 g, 1 grape 7 g, 1 berry 2 g

What your body absorbs

• In a crossover RCT in 18 adults, a 5.3 oz (150 g) serving of two blueberry varieties with different polyphenol content gave similar blood polyphenol exposure, and so did a bar containing one serving of blueberries. — Adults, mean age 42, four single-serving visits (n = 18) Evidence B source
  Serum AUC similar across berry treatments, only minor differences in Cmax and Tmax
• Pooled human absorption studies suggest about 31% of flavan-3-ols are absorbed on average, and about 25% after eating grapes, based on only two grape studies. — Healthy subjects in 49 human intervention studies Evidence C source
  Mean flavan-3-ol bioavailability 31 +/- 23%, about 25% for tea, cocoa, apples and grape
• In 14 adults with hereditary hemochromatosis, a polyphenol supplement made with grape juice extract, black tea and cocoa cut iron absorption from a meal by about 40%. — Adults with hereditary hemochromatosis (HFE p.C282Y homozygous), single test meals (n = 14) Evidence B source
  Fractional iron absorption 3.01% (1.60 to 5.64) with supplement vs 5.21% (3.92 to 6.92) with placebo, p = 0.026

What cooking and storage change

• For frozen fruit the USDA retention table keeps 70% of vitamin C, 90% of potassium and 95% of folate, which applies to frozen blueberries and grapes as fruits of that group. — USDA retention factors for the group Fruits and Fruit Juices, method FRUITS,FROZEN Evidence E source
  Vitamin C 70% retained, potassium 90%, folate 95%, iron and magnesium 100%

What it does to your health

• In a meta-analysis of 14 RCTs with 632 healthy people, eating blueberries raised flow-mediated dilation, a marker of artery function, by 1.11 percentage points. — Healthy individuals in 14 randomized controlled trials (n = 632) Evidence A source
  FMD +1.11% (95% CI 0.50 to 1.72), I2 23%
• In a crossover RCT in 25 adults with obesity, one dose of grape powder equal to 8.9 oz (252 g) of fresh grapes did not change blood glucose or triglycerides after breakfast and lunch compared with placebo. — Adults with obesity (BMI 30 to 40), single-dose crossover (n = 25) Evidence B source
  No significant difference vs placebo in postprandial glucose, triglycerides or plasma antioxidant capacity
• In an RCT of 57 cognitively healthy adults aged about 73, 20 g a day of freeze-dried blueberry powder for 24 weeks did not change blood markers of brain damage or cognitive test scores. — Cognitively healthy older adults, mean age about 73, 24 weeks (n = 57) Evidence B source
  No difference in p-tau181 or NFL (p interaction 0.10 and 0.58), diastolic BP reduced (p interaction 0.015), no effect on systolic BP or cognition
• In a crossover RCT in 24 healthy young adults, a wild blueberry drink with at least 300 mg of anthocyanins lowered blood glucose and insulin in the first hour after a high-carbohydrate breakfast. — Healthy adults, mean age 28, 22 of 24 women, single meals (n = 24) Evidence B source
  Lower glucose and insulin vs control in the first hour at medium and high doses, no effect on cognition or blood pressure

Safety, limits and interactions

• In healthy volunteers blueberry juice did not significantly raise blood levels of buspirone or flurbiprofen, unlike grapefruit juice, which doubled buspirone exposure. — Healthy volunteers, single-dose pharmacokinetic study Evidence C source
  Buspirone AUC ratio 1.39 with blueberry juice (not significant) vs 2.12 with grapefruit juice, flurbiprofen AUC ratio 1.03
• In a crossover RCT in 14 healthy volunteers, 8 oz of grape juice did not change clearance of flurbiprofen, which the authors say makes a pharmacokinetic interaction with warfarin highly unlikely. — Healthy volunteers, five crossover trials a week apart (n = 14) Evidence B source
  Flurbiprofen clearance 29 to 33 mL/min and half-life 3.3 to 3.4 h, no difference between juice arms and placebo
• A case report describes anaphylaxis in a 26-year-old woman after grapes taken with ketoprofen, diagnosed as lipid transfer protein allergy with the painkiller as a cofactor. — One adult woman (n = 1) Evidence D source
  Anaphylactic symptoms, LTP sensitization confirmed by multiplex IgE test
• In an RCT of breastfed infants aged 5 to 12 months, up to 10 g a day of blueberry powder lowered serum IL-13 against placebo, with caregiver-reported symptom differences of borderline significance. — Breastfed US infants, 5 to 12 months of age, 61 completers (n = 61) Evidence B source
  IL-13 reduced (p = 0.035), IL-10 borderline increased (p = 0.052), symptom trajectories differed (p = 0.05)
• The CDC lists uncut grapes and berries among potential choking hazards for young children. — Infants and young children (n = -) Evidence E source
  Listed as food to avoid for young children (choking risk)
• NIH ODS states that in people who cannot excrete potassium normally, because of chronic kidney disease or drugs such as ACE inhibitors or potassium-sparing diuretics, even dietary potassium intakes below the Adequate Intake can cause hyperkalemia. This includes potassium from blueberries and grapes. — people with chronic kidney disease or taking ACE inhibitors or potassium-sparing diuretics Evidence E source
  Hyperkalemia possible even below the Adequate Intake, no threshold given

What people believe that the data does not support

• Across 17 trials in people with cardiometabolic disease, blueberry or cranberry supplements lowered systolic blood pressure by only 0.81 mm Hg, which was not significant. — Patients with cardiometabolic diseases in randomized clinical trials Evidence A source
  SBP -0.81 mm Hg (95% CI -2.26 to 0.63), DBP -0.15 mm Hg (95% CI -1.36 to 1.05)
• The EU did not authorize a juice-drink claim that blueberries have anti-aging properties and maintain urinary tract and vision health. — EU health claims register, snapshot 2026-09-21 Evidence E source
  Status Non-authorized
• The EU did not authorize a claim that red grape skin extract protects cells from free-radical damage. — EU health claims register, snapshot 2026-09-21 Evidence E source
  Status Non-authorized
• Under the FDA rule updated in December 2024, plain blueberries or grapes with nothing added except water automatically qualify for the “healthy” label claim. — US food labeling: the voluntary “healthy” nutrient content claim, 21 CFR 101.65(d) as updated by FDA Evidence E source
  Fruits with no added ingredients except water qualify automatically; no food-group minimum or nutrient-limit calculation needed

Who this works differently for

• Observational data from 582 hemodialysis patients link eating grapes with less fluid overload, while cherries, carrots and bacon were linked with more. — Hemodialysis patients in 37 Portuguese centers, followed longitudinally (n = 582) Evidence C source
  Direction only in abstract: grapes associated with lower hyperhydration

What is still unknown

• The same meta-analysis of 14 RCTs found no clear effect of blueberries on executive function (SMD 0.21) or mood in healthy people, so the cognitive benefit is unproven. — Healthy individuals in randomized controlled trials Evidence A source
  Executive function SMD 0.21 (95% CI -0.05 to 0.46), mood MD 1.67 (95% CI -1.35 to 4.69), both not significant
• Whether eating grapes daily for weeks changes blood sugar after meals is untested, since the only postprandial trial in 25 adults with obesity used a single dose. — Adults with obesity (n = 25) Evidence B source
  Open question named by the trial authors

The bottom line

Across 17 trials in people with cardiometabolic disease, blueberry or cranberry supplements lowered systolic blood pressure by 0.81 mm Hg (95% CI -2.26 to 0.63), which did not reach significance. That analysis pooled both berries and mixed supplements with whole fruit. In a small trial in 57 cognitively healthy older adults, 20 g a day of freeze-dried blueberry powder for 24 weeks did not change blood markers of brain damage or cognitive test scores, and it lowered diastolic pressure as a secondary outcome. A wild blueberry drink with at least 300 mg of anthocyanins lowered blood glucose and insulin in the first hour after a high-carbohydrate breakfast in 24 young adults, 22 of them women. The abstract does not say how many fresh berries that equals. For grapes, one dose of 1.6 oz (46 g) of grape powder, equal to 8.9 oz (252 g) of fresh grapes, did not change glucose or triglycerides after meals in 25 adults with obesity, and the authors suspect the polyphenol dose was too low. They say the effect of daily grape powder over weeks remains to be worked out. In 18 adults, a 5.3 oz (150 g) serving of two blueberry varieties with different polyphenol content gave similar blood polyphenol exposure, and so did a manufactured protein bar made with one serving. Pooled absorption studies put the share of flavan-3-ols absorbed after grapes at about 25%, a figure that rests on only two grape studies. A case report describes anaphylaxis in a 26-year-old woman after grapes taken with ketoprofen, diagnosed as lipid transfer protein allergy with the painkiller as a cofactor, so grapes can be this kind of allergen at an unknown frequency. Two juices were tested against specific drugs, and only those two, so this page cannot speak for any other medicine. In 14 healthy volunteers, 8 oz of grape juice did not change clearance of flurbiprofen, which the authors say makes a warfarin interaction highly unlikely. Blueberry juice did not significantly raise buspirone levels (ratio 1.39), where grapefruit juice doubled them, in a small non-randomized study that gives no sample size. In 14 adults with hereditary hemochromatosis, a supplement of grape juice extract, black tea and cocoa cut iron absorption from a meal from 5.21% to 3.01%, about 40 percent. That was a mixed extract, and the effect of whole grapes is unknown. In 61 breastfed infants aged 5 to 12 months, up to 10 g a day of freeze-dried blueberry powder lowered serum IL-13 (p = 0.035) in a small trial with caregiver-reported symptoms and groups unbalanced at the start. The infants got powder, not whole berries, and the abstract does not report on safety, so it says nothing about giving young children whole grapes or berries. We have no card on choking risk from whole grapes or berries in young children, so this page cannot tell you how to serve them safely. In a Portuguese cohort of 582 people on hemodialysis, eating grapes went with less fluid overload, an association with no size given and not a reason for anyone on dialysis to eat more grapes. That study did not look at potassium, which in grapes runs at 229 mg per 3.5 oz (100 g). We have no card on potassium limits in kidney disease, and we found nothing on pregnancy for either fruit. The EU refused a juice-drink claim that blueberries have anti-aging properties and maintain urinary tract and vision health, and a claim that red grape skin extract protects cells from free-radical damage. The register snapshot does not give the reasons. In the US, plain blueberries or grapes with nothing added except water automatically qualify for the voluntary "healthy" label claim under the FDA rule of December 2024. That claim says a food fits a healthy eating pattern and makes no promise about disease.

Sources

1. bbgr-daily-r8-18 · USDA FoodData Central Foundation Foods, dataset
   Blueberries, raw: vitamin C 8.059 mg per 100 g (range 4.295-11.1, 8 samples); potassium 85.64 mg (74.2-109.5, 8 samples); fructose 4.939 g; glucose 4.417 g. Grapes, red, seedless, raw: vitamin C 3.308 mg (2.18-4.905, 8 samples); potassium 229.4 mg (169.0-273.0, 8 samples); fructose 9.167 g; glucose 8.174 g
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-09-28
2. bbgr-daily-r8-19 · CoFID 2021, dataset
   CoFID 14-325 Blueberries: energy 40 kcal, total sugars 9.1 g, AOAC fibre 1.5 g, potassium 66 mg, manganese 0.69 mg per 100 g. CoFID 14-350 Grapes, average: energy 65 kcal, total sugars 16.1 g, AOAC fibre 1.3 g, potassium 215 mg, manganese 0.06 mg per 100 g
   CoFID 2021, Public Health England, OGL v3.0, codes 14-325 and 14-350 · checked 2026-09-28
3. bbgr-daily-r8-20 · USDA FNDDS, dataset
   Blueberries, raw (FNDDS 63203010, fdc 2709275): 1 berry 2 g; 1 cup 150 g; Quantity not specified 75 g. Grapes, raw (FNDDS 63123000, fdc 2709237): 1 grape 7 g; 1 cup 150 g; Quantity not specified 75 g
   USDA FNDDS 2021-2023 via FoodData Central, FDC 2709275 and 2709237 · checked 2026-09-28
4. bbgr-daily-r8-08 · RCT
   This blinded, randomized, 4-way crossover, controlled trial (n = 18; 42.06 ± 12.53 y; body mass index [BMI] 24.75 ± 2.97 kg/m2) fed 1 serving (150 g) of Elliott and Olympia blueberries and a (poly)phenol-rich protein bar containing 1 serving of Elliott blueberries ... Serum AUC was similar across berry-derived treatments ... Differing berry (poly)phenol content and bioaccessibility only minimally affect bioavailability following consumption of blueberries relative to a blueberry-rich protein bar
   Am J Clin Nutr, 2025 · checked 2026-09-28
5. bbgr-daily-r8-09 · systematic review
   Mean bioavailability for flavan-3-ols was moderate (31 ± 23%, n bioavailability values = 20), and it seems to be scarcely affected by the amount of ingested compounds. ... followed by 25% after consumption of tea (n = 7), cocoa (n = 5), apples (n = 3) and grape (n = 2).
   Mol Aspects Med, 2023 · checked 2026-09-28
6. bbgr-daily-r8-10 · RCT
   formulated a polyphenol supplement (PPS) containing black tea powder, cocoa powder and grape juice extract. ... In the iron absorption study, the PPS reduced FIA by ~ 40%: FIA from the meal consumed with the PPS was lower (3.01% (1.60, 5.64)) than with placebo (5.21% (3.92, 6.92)) (p = 0.026))
   Eur J Nutr, 2022 · checked 2026-09-28
7. bbgr-daily-r8-21 · USDA Nutrient Retention Factors R6, dataset
   USDA-RETN-R6:156 Fruits and Fruit Juices, FRUITS,FROZEN: vitamin_c_mg 70%; potassium_mg 90%; folate_total_ug 95%; iron_mg 100%; magnesium_mg 100%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), code 156 · checked 2026-09-28
8. bbgr-daily-r8-01 · meta-analysis of RCTs
   we analyzed 14 randomized controlled trials (RCTs) involving 632 participants. 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.
   Nutr Res, 2026 · checked 2026-09-28
9. bbgr-daily-r8-04 · RCT
   Twenty-five obese subjects (BMI = ≥ 30 and < 40 kg/m2) were randomly divided into two groups. ... the subjects received breakfast and 46 g of either grape powder (equivalent to 252 g fresh grapes) or placebo, both solved in water. ... The grape powder supplementation did not cause any significant modification compared to placebo, in these parameters; nor did it significantly modify plasma antioxidant capacity in the 6 h postprandial period.
   Eur J Nutr, 2021 · checked 2026-09-28
10. bbgr-daily-r8-06 · RCT
    57 cognitively healthy subjects were assigned either 20 g/d of freeze-dried blueberry powder or matching placebo for 24 weeks. ... In secondary aims, blueberry intervention reduced diastolic blood pressure (p interaction with time 0.015) but there was no effect on systolic blood pressure, cognitive tests, and other biomarkers. CONCLUSION: A 24-week intervention with freeze-dried blueberries had no effect on serum p-tau181 and serum NFL in older adults.
    Clin Nutr ESPEN, 2026 · checked 2026-09-28
11. bbgr-daily-r8-07 · RCT
    Twenty-four healthy participants (F = 22), mean BMI 22.9 kg/m2 and mean age 28 years were recruited to a randomized crossover study ... Medium and high doses showed significantly lower glucose and insulin compared to control during the first hour. ... Wild blueberry effects on postprandial glucose and appetite hormone responses were evident at anthocyanin doses of 300 mg and above but did not impact other outcomes in healthy adults.
    Eur J Nutr, 2026 · checked 2026-09-28
12. bbgr-daily-r8-11 · controlled clinical trial
    In clinical studies, GFJ significantly increased area under the plasma concentration-time curve (AUC) for the CYP3A substrate buspirone. The geometric mean ratio (GMR = AUC with GFJ divided by AUC with water) was 2.12. In contrast, the effect of BBJ (GMR = 1.39) was not significant. In the study of flurbiprofen (CYP2C9 substrate), the positive control inhibitor fluconazole significantly increased flurbiprofen AUC (GMR = 1.71), but BBJ had no significant effect (GMR = 1.03).
    Br J Clin Pharmacol, 2013 · checked 2026-09-28
13. bbgr-daily-r8-12 · RCT
    In a clinical study 14 healthy volunteers received 100 mg flurbiprofen on 5 occasions in a crossover fashion, with at least 1 week separating the 5 trials. ... Flurbiprofen clearance (29-33 mL/min) and elimination half-life (3.3-3.4 hours) did not differ significantly among trials 1, 2, 3, and 4. ... none of the 3 beverages altered CYP2C9-mediated clearance of flurbiprofen in humans, making a pharmacokinetic interaction with warfarin highly unlikely.
    Clin Pharmacol Ther, 2006 · checked 2026-09-28
14. bbgr-daily-r8-13 · case report
    This case report describes a 26-year-old female who developed anaphylactic symptoms after ingesting grapes and taking ketoprofen. ... A diagnosis of LTP allergy and selective ketoprofen allergy was made, with the recommendation to avoid ketoprofen and follow a diet excluding foods from the LTP group.
    Int J Mol Sci, 2025 · checked 2026-09-28
15. bbgr-daily-r8-14 · RCT
    infants from the Denver metro area were assigned to receive up to 10 g/day of freeze-dried blueberry powder or an isocaloric placebo from 5 to 12 months of age. ... Of the 76 infants enrolled, 61 completed the study (Blueberry: n = 30; Placebo: n = 31). ... Pro-inflammatory serum IL-13 levels were significantly reduced (p = 0.035) and anti-inflammatory IL-10 levels borderline increased (p = 0.052) in the blueberry group.
    Nutrients, 2025 · checked 2026-09-28
16. sf-choke-1 · agency advice
    Uncut grapes, berries, cherries, or melon balls.
    CDC, Infant and Toddler Nutrition: Choking Hazards · checked 2026-10-08
17. sf-khyp-r1-bluegrape-1 · agency advice
    However, in people with impaired urinary potassium excretion due to chronic kidney disease or the use of certain medications, such as angiotensin converting enzyme (ACE) inhibitors or potassium-sparing diuretics, even dietary potassium intakes below the AI can cause hyperkalemia.
    NIH Office of Dietary Supplements, Potassium Fact Sheet for Health Professionals · checked 2026-10-08
18. bbgr-daily-r8-03 · meta-analysis of RCTs
    A total of 17 articles were included, from which two found significant results from blueberry and/or cranberry supplementation in reducing BP. Pooled results revealed statistically non-significant reductions of -0.81 mm Hg for SBP (95% confidence interval [CI]: -2.26, 0.63; I2 = 0%) and -0.15 mm Hg for DBP (95% CI: -1.36, 1.05; I2 = 27%).
    Phytother Res, 2024 · checked 2026-09-28
19. bbgr-daily-r8-16 · EU claims register
    POL-HC-7636 Name of Food product: Sqeez Wild Blueberry Juice Drink Description of food in terms of food legislation categories: food not covered by specific food legislation Was food on Irish market before 1st July 2007: Yes Exact wording of claim as it appears on product: Blueberries have a wide range of health benefits including anti-ageing properties and the maintenance of urinary tract and vision health Is claim a picture: No Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-7636, snapshot 2026-09-21 · checked 2026-09-28
20. bbgr-daily-r8-17 · EU claims register
    POL-HC-7081 Extract from the red grapes skin Helps to protect cells from the free-radical damage Helps to protect cells from the damage caused by free-radical Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-7081, snapshot 2026-09-21 · checked 2026-09-28
21. bbgr-webfix-1-01 · US federal regulation (agency explainer page)
    Under the updated ”healthy” claim, nutrient-dense foods that are encouraged by the Dietary Guidelines – vegetables, fruits, whole grains, fat-free and low-fat dairy, lean game meat, seafood, eggs, beans, peas, lentils, nuts, and seeds – with no added ingredients except for water, automatically qualify for the “healthy” claim because of their nutrient profile and positive contribution to an overall healthy diet.
    US FDA, Use of the “Healthy” Claim on Food Labeling (final rule of December 19, 2024) · checked 2026-09-29
22. bbgr-daily-r8-15 · cohort
    This observational, longitudinal study includes 582 patients from 37 Portuguese HD centers. ... Consumption of bacon, savory snacks, carrots, bell peppers, cherries, and soup predicted greater hyperhydration, while rice, cookies, and grapes show the opposite effect, regardless of age, sex, diabetes, and HD duration.
    Clin Nutr ESPEN, 2026 · checked 2026-09-28
23. bbgr-daily-r8-02 · meta-analysis of RCTs
    Cognitive outcomes showed no significant effect executive function (SMD: 0.21; 95% CI: -0.05, 0.46; I² = 42%) or mood (MD: 1.67; 95% CI: -1.35, 4.69; I² = 10%).
    Nutr Res, 2026 · checked 2026-09-28
24. bbgr-daily-r8-05 · RCT
    The result of a combination of grape with other polyphenol-rich products or chronic supplementation with grape powder on postprandial responses remains to be elucidated.
    Eur J Nutr, 2021 · checked 2026-09-28