Prune juice: one small trial behind a big reputation

A 2024 meta-analysis of 23 studies in 1714 adults with chronic constipation found exactly one trial of prune juice to include. That trial is small and positive. In 84 Japanese adults with chronic constipation, 1.9 oz (54 g) of prune juice a day lowered the share of hard, lumpy stools below placebo from the third week of an 8 week study, without adding loose stools. The paper shows the size of that effect only in figures, from a single site. Most of the reputation belongs to whole prunes. A review found four trials of the fruit, with unclear risk of bias in two, and in one of them 3.5 oz (100 g) of prunes a day for 3 weeks gave 3.5 complete bowel movements a week against 2.8 on psyllium. When the 2024 meta-analysis pooled the prune trials, prunes did no better than psyllium on stool frequency. In people whose bowels already work normally, five trials of added fruit fiber, two of them with whole prunes, found no change in stool form (mean difference 0.02, 95% CI -0.15 to 0.20).

The numbers, per 3.5 oz (100 g)

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• UK data list prune juice at 57 calories and 14.4 g sugars per 3.5 oz (100 g), mostly glucose, with 210 mg potassium and only trace fiber. — CoFID 2021 Prune juice (14-289) (n = 1 record) Evidence E source
  Per 100 g: 57 calories, sugars 14.4 g (glucose 10.0 g, fructose 4.4 g), potassium 210 mg, iron 0.70 mg, NSP fiber trace
• Prune juice has so little nitrate, under 0.01 mmol in 5.6 fl oz (166 mL), that trials use it as a nitrate-free placebo for beet juice. — Commercial prune juice (Sunsweet) used as control drink in a crossover trial of 16 young adults Evidence D source
  Less than 0.01 mmol nitrate per 166 mL vs about 8 mmol in 4.7 fl oz (140 mL) beetroot juice

What a real portion looks like

• A typical US serving of prune juice is 248 g, about one cup, carrying roughly 685 mg potassium and 41 g sugars. — USDA FNDDS Prune juice, 100% (64132010, fdc_id 2709331) (n = 4 measures) Evidence E source
  Per 100 g: potassium 276 mg, total sugars 16.45 g; 8.7 oz (248 g) serving: 684.5 mg potassium, 40.8 g sugars; 1 fl oz 31 g

What cooking and storage change

• Heating a prune juice already holding 188 ug/kg acrylamide at 95 C for 24 hours raised it to 438 ug/kg, pointing to prolonged boiling as a source. — Commercial prune juice and simulated plum juice heated under drying and wet conditions Evidence D source
  188 to 438 ug/kg after 95 C for 24 h open vessel; 375 ug/kg after 120 C for 1 h closed vessel

What it does to your health

• In 84 Japanese adults with chronic constipation, 1.9 oz (54 g) of prune juice a day cut hard stools versus placebo within 3 weeks. — 84 adults aged 20-75 with treatment-naive chronic constipation (Rome IV), 54 g test drink daily for 8 weeks (n = 84) Evidence B source
  Hard and lumpy stool rate significantly lower than placebo from week 3; loose stools not increased
• In 166 healthy volunteers, drinking the soaking water of about 3 prunes plus the fruit daily for 8 weeks modestly lowered serum ALT (p 0.048). — 166 healthy volunteers randomized to 3 prunes (11.43 g), 6 prunes (23 g) soaked in 8.5 fl oz (250 ml) water, or water, 8 weeks (n = 166) Evidence B source
  Lower serum ALT (p 0.048) and alkaline phosphatase (p 0.017) at the lower dose only; AST and bilirubin unchanged

Safety, limits and interactions

• Over 8 weeks of daily prune juice in 84 constipated adults, no adverse events or liver or kidney lab abnormalities appeared. — 84 adults with chronic constipation, prune juice or placebo daily for 8 weeks (n = 84) Evidence B source
  No adverse events; no liver or renal laboratory abnormalities; loose and watery stools unchanged
• US prune juice measured 138 to 268 ug/kg acrylamide, so a 8.5 fl oz (250 mL) glass at 250 ug/kg supplies about 62.5 ug. — Prune juice sold in the United States (FDA survey figures cited by the authors) Evidence D source
  138-268 ug/kg in US prune juice; about 62.5 ug per 250 mL glass

What people believe that the data does not support

• Most prune evidence is for whole fruit: 3.5 oz (100 g) of prunes a day for 3 weeks gave 3.5 vs 2.8 complete bowel movements a week compared with psyllium. — Four RCTs of prunes, one in constipated adults (prunes 100 g/day vs psyllium 22 g/day, 3 weeks) (n = 4 RCTs) Evidence B source
  3.5 vs 2.8 CSBM per week (P = 0.006); stool consistency 3.2 vs 2.8 (P = 0.02)
• The EU did not authorize claims that prune juice has a natural laxative effect or supports bowel regularity. — EU nutrition and health claims register Evidence E source
  Status Non-authorized

Who this works differently for

• In people without constipation, added fruit fiber including prunes did not change stool consistency across five trials (mean difference 0.02). — Adults with normal bowel function in 5 trials of added fruit fiber (two of prunes, 4 to 7 g/day fiber) (n = 5 trials) Evidence A source
  Bristol stool score MD 0.02 (95% CI -0.15 to 0.20); frequency +0.4 per week (95% CI -0.1 to 0.9), not significant
• Among 24 baby prune foods on the Canadian market, one brand of strained prunes held more than three times the acrylamide of another. — 24 baby foods and 18 other prune products bought in Canada in 2009 (n = 42) Evidence D source
  Brand A strained prune baby food more than 3x acrylamide of brand B

What is still unknown

• A 2024 meta-analysis of 23 studies in 1714 constipated adults found just one prune juice trial, and prunes did not beat psyllium on stool frequency. — 1714 adults with chronic constipation in 23 intervention studies (17 RCTs) (n = 1714) Evidence A source
  Prunes vs psyllium: no difference in stool frequency; prune juice studied in a single trial

The bottom line

A glass is mostly sugar and water. USDA survey data put a typical US serving at 248 g, about a cup, with roughly 685 mg potassium and 41 g sugars, recalculated from the per 3.5 oz (100 g) values. UK data list 57 calories and 14.4 g sugars per 3.5 oz (100 g), mostly glucose, with 210 mg potassium and only a trace of fiber. The two datasets disagree on potassium, 276 against 210 mg per 3.5 oz (100 g). Prune juice has almost no nitrate, under 0.01 mmol in 5.6 fl oz (166 mL) of one brand, so sports scientists use it as a placebo for beetroot juice. A homemade version has one trial. In 166 healthy volunteers, drinking the soaking water of about 3 prunes with the fruit every day for 8 weeks lowered serum ALT (p 0.048) and alkaline phosphatase at the lower dose only. The paper gives no effect size and no clinical outcome, so it says little about the liver. In the 8 week constipation trial, the 84 adults on prune juice or placebo had no adverse events and no liver or kidney lab abnormalities. A trial that size cannot catch rare harms, and bloating was not scored. Acrylamide is the contaminant to know about. US prune juice has measured 138 to 268 micrograms per kg, and a 8.5 fl oz (250 mL) glass at 250 micrograms per kg would supply about 62.5 micrograms, an exposure estimate with no health outcome attached. In a model experiment, heating a juice at 95 C for 24 hours raised its acrylamide from 188 to 438 micrograms per kg, which points to long boiling in manufacture. For parents, among 24 prune baby foods bought in Canada in 2009, one brand of strained prunes held more than three times the acrylamide of another. We have no trial of prune juice in infants or children, in pregnancy or alongside medicines, and no figure for how much sorbitol a glass holds. The EU register lists the claims that prune juice is a natural laxative or helps bowel regularity as not authorized, meaning the evidence fell short when it was assessed.

Sources

1. prj-daily-r3-07 · food composition dataset
   Prune juice (14-289): Energy 57 kcal | Total sugars 14.4 g | Glucose 10.0 g | Fructose 4.4 g | Potassium 210 mg | Iron 0.70 mg | NSP Tr
   CoFID 2021 (Public Health England, OGL v3.0), code 14-289 Prune juice · checked 2026-09-29
2. prj-daily-r3-13 · composition statement
   placebo control beverage (CON) consisting of prune juice (Sunsweet®; POKKA SAPPORO Food & Beverage Ltd., Nagoya, Japan; 166 mL/day; <0.01 mmol NO3−). We selected prune juice as the placebo beverage because the NO3− in prune juice is at a negligible level and the carbohydrate and fiber contents of prune juice are similar to those of BRJ
   Nutrients, 2022 · checked 2026-09-29
3. prj-daily-r3-08 · reference dataset
   Prune juice, 100%, FNDDS 64132010, fdc_id 2709331: Quantity not specified 248 g | 1 fl oz (no ice) 31 g || Potassium 276 mg | Total Sugars 16.45 g per 100 g
   USDA FNDDS (FoodData Central survey), Prune juice, 100%, food code 64132010, fdc_id 2709331 · checked 2026-09-29
4. prj-daily-r3-09 · laboratory food analysis
   Prune juice is produced by boiling the prunes in water until soluble solid content reaches approximately 18% and some processes might also include pasteurisation. ... When an actual prune juice sample already containing 188 μg kg−1 of acrylamide was heated at 95°C for 24 h (drying condition, open vessel), the concentration of acrylamide increased to 438 μg kg−1. ... It is probable that prolonged boiling and/or pasteurisation are responsible for the observed increase in acrylamide.
   Becalski A et al. Formation of acrylamide at temperatures lower than 100 C: the case of prunes and a model study. Food Addit Contam Part A, 2011 · checked 2026-09-29
5. prj-daily-r3-01 · randomized controlled trial
   Subjects were randomly assigned to the prune juice group or placebo group and consumed 54 g of each test food in a day for 8 weeks. ... A total of 84 subjects were enrolled and included in the intention-to-treat analysis ... In the prune juice group, the rates of hard and lumpy stools (BSFS 1 or 2) were significantly decreased from baseline and were significantly lower than the placebo group after 3 weeks (Figure 1).
   Am J Gastroenterol, 2022 · checked 2026-09-29
6. prj-daily-r3-12 · randomized controlled trial
   166 healthy volunteers were divided into three groups randomly. Either three (about 11.43g) or six (23g approx.) prunes were soaked in a glass of water (250ml) overnight. ... There was significant reduction of serum alanine transaminase (p 0.048) and serum alkaline phosphatase (p 0.017) by the lower dose of prunes.
   Pak J Pharm Sci, 2010 · checked 2026-09-29
7. prj-daily-r3-02 · randomized controlled trial
   A total of 84 subjects were enrolled and included in the intention-to-treat analysis ... During the study period, there were no AEs or laboratory abnormalities of liver or renal function based on the Common Terminology Criteria for Adverse Events definition between baseline and postintake period in either group (Table 1).
   Am J Gastroenterol, 2022 · checked 2026-09-29
8. prj-daily-r3-10 · laboratory food analysis
   The levels of acrylamide in prune juice reported in the United States ranged from 138 to 268 μg kg−1 and in pitted prunes themselves from 31 to 87 μg kg−1. ... Consumption of a glass (250 ml) of prune juice at a level of 250 μg kg−1 would provide a 62.5 μg intake of acrylamide.
   Becalski A et al. Formation of acrylamide at temperatures lower than 100 C: the case of prunes and a model study. Food Addit Contam Part A, 2011 · checked 2026-09-29
9. prj-daily-r3-04 · systematic review
   In constipation, 3 weeks of prune consumption (100 g/day) improved stool frequency (3.5 vs. 2.8 CSBM per week, P = 0.006) and stool consistency (3.2 vs. 2.8 on Bristol stool form scale, P = 0.02) compared with psyllium (22 g/day).
   Aliment Pharmacol Ther, 2014 · checked 2026-09-29
10. prj-daily-r3-06 · regulatory decision
    POL-HC-7843 Prune Juice Prune juice help the maintenance of healthy body function. Prune juice help with the maintenance of health in general Prune juice helps maintain bowel regularity which can help to ensure a healthy digestion and bowel. Prune juice is beneficial to the health of the stomach and digestive system. Prune juice is good for healthy bowel function. Prune juice is good for (regular) digestion Prune juice has a natural laxative effect that can contribute to a healthy digestion and bowel. Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-7843, snapshot 2026-09-21 · checked 2026-09-29
11. prj-daily-r3-05 · systematic review (AHRQ)
    Two studies evaluated prunes (4, 6, and 7 g/day added fiber) ... By meta-analysis (Figure 39), there was no significant difference in BSS scores, with a summary MD of 0.02 (95% CI −0.15 to 0.20).
    AHRQ, Fiber Intake and Laxation in People With Normal Bowel Function: Systematic Review, 2025 · checked 2026-09-29
12. prj-daily-r3-11 · laboratory food analysis
    Retail food samples were collected in 2009; they included 24 baby foods and 18 other prune products. ... For example, in the strained prune baby food category, brand A contains, on average, more than three times the amount of acrylamide found in brand B.
    Becalski A et al. Formation of acrylamide at temperatures lower than 100 C: the case of prunes and a model study. Food Addit Contam Part A, 2011 · checked 2026-09-29
13. prj-daily-r3-03 · meta-analysis
    We included 23 studies (17 RCTs, 6 uncontrolled; 1714 participants): kiwifruit (n = 7), high-mineral water (n = 4), prunes (n = 2), rye bread (n = 2), mango, fig, cereal, oat bran, yoghurt, water supplementation, prune juice, high-fibre diet, no-fibre diet (n = 1). ... there was no difference for prunes compared with psyllium.
    Aliment Pharmacol Ther, 2024 · checked 2026-09-29