Bananas and blueberries: four times the potassium against one vessel trial

The strongest evidence on this page belongs to blueberries. Across 14 randomized trials with 632 healthy people, eating blueberries improved blood vessel dilation, a measure called flow-mediated dilation, by 1.11 percentage points (95% CI 0.50 to 1.72), while systolic blood pressure did not change (-0.11 mmHg). Doses and forms ranged from powder to fresh fruit, and vessel dilation is a surrogate marker. The banana's best result is narrower. Across 9 randomized trials in 3,996 children aged 8 to 34 months with diarrhea, adding green, unripe banana foods to standard care, not replacing it, nearly doubled the rate of recovery (HR 1.96, 95% CI 1.62 to 2.37), though 7 of the 9 trials were open label. On the plate the two fruits differ mostly in potassium. USDA measured 326 mg per 3.5 oz (100 g) in ripe bananas against 86 mg in raw blueberries. One 126 g banana carries about 122 calories, and a 150 g cup of blueberries about 96 calories. We found no study comparing the two directly.

How much is actually in it

• USDA measured almost four times more potassium in ripe bananas (326 mg per 3.5 oz (100 g)) than in raw blueberries (86 mg per 3.5 oz (100 g)). — USDA Foundation Foods: Bananas, ripe and slightly ripe, raw (6 samples); Blueberries, raw (8 samples) (n = 14) Evidence E source
  Banana 326 mg (300-355); blueberries 85.64 mg (74.2-109.5) per 3.5 oz (100 g)
• Vitamin C is low in both fruits: USDA measured 12.3 mg per 3.5 oz (100 g) in ripe bananas and 8.1 mg in raw blueberries, with wide sample-to-sample spread. — USDA Foundation Foods: Bananas, ripe and slightly ripe, raw (12 samples); Blueberries, raw (8 samples) (n = 20) Evidence E source
  Banana 12.3 mg (9.2-15.1); blueberries 8.059 mg (4.295-11.1) per 3.5 oz (100 g)

What a real portion looks like

• In the USDA survey food table one banana (126 g) carries about 122 calories, and one cup of raw blueberries (150 g) about 96 calories. — USDA FNDDS: Banana, raw (fdc 2709224); Blueberries, raw (fdc 2709275) Evidence E source
  Banana 97 calories/100 g, 1 banana 126 g 122.2 calories; blueberries 64 calories/100 g, 1 cup 150 g 96 calories

What your body absorbs

• In a crossover trial in 8 healthy men, a banana smoothie cut peak blood levels of cocoa-type flavanols by 84% compared with capsules, while a mixed berry smoothie did not. — Healthy men, n = 8 (plus n = 11 in a follow-up study) (n = 8) Evidence B source
  Cmax 96 vs 680 nmol/L (-84%) with high-PPO banana drink; low-PPO berry drink similar to capsule
• In a crossover trial in 9 people eating 8.8 oz (250 g) of blueberries, whole fruit raised 108 urinary metabolites more than juice, while juice raised only 8 more, 2 hours after eating. — Nine healthy subjects, 250 g fresh blueberries as whole fruit or juice (n = 9) Evidence B source
  108 urinary ions higher after whole berries vs 8 higher after juice at 2 h

What cooking and storage change

• By the USDA retention table for frozen fruits, about 70% of vitamin C and 90% of potassium remain, which applies to frozen bananas and blueberries alike. — USDA Table of Nutrient Retention Factors Release 6, Fruits and Fruit Juices (code 9), method 156 FRUITS,FROZEN Evidence E source
  Vitamin C 70%, potassium 90%, folate 95%, magnesium 100%
• Baking blueberries into products cut their anthocyanins by 42%, yet in a crossover trial in 10 volunteers the baked products improved blood vessel function as much as an unprocessed blueberry drink. — Ten healthy volunteers (n = 10) Evidence B source
  Anthocyanins -42% after baking; FMD rose at 1, 2 and 6 h similarly to unprocessed blueberries

What it does to your health

• Across 14 randomized trials with 632 healthy people, eating blueberries improved blood vessel dilation by 1.11 percentage points but did not change systolic blood pressure. — Healthy individuals in 14 RCTs (n = 632) Evidence A source
  FMD +1.11% (95% CI 0.50 to 1.72); SBP -0.11 mmHg (-2.82 to 2.60); executive function SMD 0.21 (-0.05 to 0.46)
• Cohort data from 451,291 adults link each extra 7.1 oz (200 g) of fruit a day with a 7% lower risk of hypertension, with inverse associations for blueberries among individual fruits. — Adults in 18 prospective studies, 145,492 hypertension cases (n = 451291) Evidence C source
  RR 0.93 (95% CI 0.89 to 0.98) per 200 g/day of fruit; blueberries inverse (n = 2-5 studies)

Safety, limits and interactions

• One case report describes a man on warfarin whose INR fell below target after dried banana flakes were started for diarrhea, rated a probable interaction. — One man in his 30s on warfarin, hospitalized (n = 1) Evidence D source
  Subtherapeutic INR for 3 days after banana flakes; interaction probability score 5 (probable)
• In Ethiopian market surveys, 38% of bananas sampled carried parasites, making banana the most contaminated fruit, with a very wide confidence interval (2% to 57%). — 3,769 raw fruits and vegetables from local markets in 13 cross-sectional studies, Ethiopia (n = 3769) Evidence C source
  Banana contamination 38.34% (95% CI 1.84 to 56.83); all produce 43.38%

What people believe that the data does not support

• A meta-analysis of 17 trials found blueberry or cranberry supplements did not meaningfully lower blood pressure in people with cardiometabolic disease (-0.81 mmHg systolic, not significant). — Patients with cardiometabolic diseases in RCTs to August 2023 Evidence A source
  SBP -0.81 mmHg (95% CI -2.26 to 0.63); DBP -0.15 mmHg (-1.36 to 1.05)
• The EU did not authorize the claim that blueberries have anti-aging properties and maintain urinary tract and vision health. — EU health claim assessment, claim POL-HC-7636 Evidence E source
  Non-authorized

Who this works differently for

• Across 9 randomized trials in 3,996 children aged 8 to 34 months, adding green banana foods to standard care nearly doubled the rate of diarrhea resolution. — Children aged 8 to 34 months with acute or persistent diarrhea (n = 3996) Evidence A source
  HR 1.96 (95% CI 1.62 to 2.37); persistent diarrhea HR 2.34, acute HR 1.74
• In a placebo-controlled trial in 61 breastfed infants given up to 10 g a day of blueberry powder from 5 to 12 months, allergy-type symptoms resolved more often than on placebo. The abstract does not report safety separately. — Breastfed US infants aged 5 to 12 months, 76 enrolled, 61 completed (n = 61) Evidence B source
  Greater resolution of allergy-related symptoms (p = 0.05); IL-13 reduced (p = 0.035)

The bottom line

Berry supplements for blood pressure do not hold up. A meta-analysis of 17 trials in people with cardiometabolic disease found blueberry or cranberry supplements lowered systolic pressure by 0.81 mmHg, which was not significant (95% CI -2.26 to 0.63). Most of those trials used supplements and pooled the two berries. Cohort data from 451,291 adults link each extra 7.1 oz (200 g) of fruit a day with a 7% lower risk of hypertension (RR 0.93), and blueberries were among the fruits with an inverse association, based on 2 to 5 studies. That is association, and bananas were not named in it. The EU refused a juice maker's claim that blueberries are anti-aging and protect the urinary tract and vision. A refused claim is a verdict on the wording and is no proof the fruit does nothing. How you eat them changes what reaches the blood. In a crossover trial in 8 healthy men, a banana smoothie cut peak blood levels of cocoa-type flavanols by 84% compared with capsules, while a mixed berry smoothie did not. The flavanols were added to the drinks, and the group was tiny. In a crossover trial in 9 people, 8.8 oz (250 g) of whole blueberries raised 108 urinary metabolites more than the same berries juiced, and juice raised only 8, at a single point 2 hours after eating. Baking blueberries into products cut their anthocyanins by 42%, yet in 10 volunteers the baked products, made with freeze-dried powder, improved vessel dilation over 6 hours as much as unprocessed blueberries. Freezing keeps about 70% of vitamin C and 90% of potassium by the USDA table for frozen fruit, a 1975 factor for fruit in general. Vitamin C is low in both anyway, 12.3 mg per 3.5 oz (100 g) in bananas and 8.1 mg in blueberries. Who should take care. One case report describes a man on warfarin whose INR fell below target after dried banana flakes were started for diarrhea, rated a probable interaction. It is a single case, but it is worth telling whoever checks your INR before you start banana flakes. In Ethiopian market surveys 38% of bananas carried parasites, with a confidence interval from 2% to 57%, in one country only. For infants, a trial in 61 breastfed babies given up to 10 g a day of freeze-dried blueberry powder from 5 to 12 months found that parent-reported allergy-type symptoms resolved more often than on placebo (p = 0.05). The abstract we read does not report safety separately.

Sources

1. bnbl-r2-01 · food composition dataset
   Bananas, ripe and slightly ripe, raw | Potassium, K | 326.0 MG | range 300.0-355.0, 6 samples || Blueberries, raw | Potassium, K | 85.64 MG | range 74.2-109.5, 8 samples
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-09-29
2. bnbl-r2-02 · food composition dataset
   Bananas, ripe and slightly ripe, raw | Vitamin C, total ascorbic acid | 12.3 MG | range 9.2-15.1, 12 samples || Blueberries, raw | Vitamin C, total ascorbic acid | 8.059 MG | range 4.295-11.1, 8 samples
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-09-29
3. bnbl-r2-03 · survey food dataset
   Banana, raw | fdc_id 2709224 | Energy 97 kcal/100 g | 1 banana 126 g 122.2 kcal || Blueberries, raw | fdc_id 2709275 | Energy 64 kcal/100 g | 1 cup 150 g 96.0 kcal
   USDA FNDDS 2021-2023 · checked 2026-09-29
4. bnbl-r2-05 · Crossover RCT
   a controlled, single blinded and cross-over study was conducted in healthy men (n = 8) who consumed a flavan-3-ol-containing banana-based smoothie (high-PPO drink), a flavan-3-ol-containing mixed berry smoothie (low-PPO drink) and flavan-3-ols in a capsule format (control)... In contrast, the intake of the high PPO drink resulted in a Cmax of 96 ± 47 nmol L-1, 84% lower than that obtained after capsule intake.
   Food Funct, 2023 · checked 2026-09-29
5. bnbl-r2-06 · Crossover RCT
   Nine healthy subjects consumed 250 g of fresh blueberries either as the whole fruit or after juicing, and provided blood and urine samples before and 2 h after intake in a cross-over design... In urinary samples, whole blueberry treatment resulted in 108 ions that were significantly higher compared with juiced treatment (positive and negative mode combined), whereas only eight were significantly higher after juiced treatment.
   Br J Nutr, 2018 · checked 2026-09-29
6. bnbl-r2-04 · retention factor table
   USDA-RETN-R6:156 FRUITS,FROZEN, group Fruits and Fruit Juices: vitamin_c_mg 70% retained, potassium_mg 90%, folate_total_ug 95%, magnesium_mg 100%
   USDA Table of Nutrient Retention Factors, Release 6, 2007, Retn_Code 156 · checked 2026-09-29
7. bnbl-r2-07 · Crossover RCT
   Although processing did not significantly change the total (poly)phenolic amount, the processed products contained significantly less anthocyanins (-42%), more chlorogenic acid (23%), no flavanol nonamers or decamers, and significantly more flavanol dimers and trimers (36% and 28%, respectively). FMD increased after 1, 2, and 6 h consumption of the baked products to a similar degree as the unprocessed blueberries
   Mol Nutr Food Res, 2014 · checked 2026-09-29
8. bnbl-r2-08 · 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. However, there were no significant changes in systolic blood pressure (SBP) (reduction of 0.11 mmHg; 95% CI: -2.82, 2.60; I² = 0%)
   Nutr Res, 2026 · checked 2026-09-29
9. bnbl-r2-11 · Meta-analysis of cohorts
   Eighteen prospective studies (451 291 participants, 145 492 cases) were included. The summary RR (95% CI) of hypertension per 200 g/day was 0.97 (0.95-0.99, I2 = 68%, n = 8) for fruits and vegetables, 0.93 (0.89-0.98, I2 = 77%, n = 10) for fruits, and 1.00 (0.98-1.02, I2 = 38%, n = 10) for vegetables... Inverse associations were observed for apples or pears, blueberries, raisins or grapes, avocado, broccoli, carrots and lettuce
   Eur J Nutr, 2023 · checked 2026-09-29
10. bnbl-r2-12 · Case report
    A probability score of 5 was obtained upon applying the Drug Interaction Probability Scale modified to address interactions between warfarin and dietary supplements, indicating a probable interaction between warfarin and banana flakes.
    Nutr Clin Pract, 2016 · checked 2026-09-29
11. bnbl-r2-14 · Meta-analysis
    Banana has emerged to be the most frequently contaminated fruit with a contamination prevalence of 38.34% (95% CI: [1.84, 56.83]).
    BMC Infect Dis, 2024 · checked 2026-09-29
12. bnbl-r2-10 · 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 2026-09-29
13. bnbl-r2-15 · Regulatory 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 2026-09-29
14. bnbl-r2-09 · Meta-analysis of RCTs
    Studies were conducted in the pediatric population comprising a total of 3996 patients aged 8 to 34 months, eight studies were written in English and one in Spanish. GB-based food consumption significantly increased the hazard of resolution of diarrhea compared to standard treatment (HR 1.96, 95% CI [1.62; 2.37], p < 0.01; I2 = 52%).
    Eur J Pediatr, 2024 · checked 2026-09-29
15. bnbl-r2-13 · 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). While more infants in the blueberry group had allergy-related symptoms at baseline, they had significantly different longitudinal symptom trajectories than the placebo (p = 0.05), showing a greater resolution rate of symptoms by study end.
    Nutrients, 2025 · checked 2026-09-29