Prunes increased stool weight and frequency in healthy adults
What it found
Eating 80 g or 120 g of prunes daily for four weeks increased stool weight and bowel movement frequency in healthy adults.
It also raised levels of one type of gut bacteria.
What they found
Studies in people
Stool weight increased
Both prune groups gained more stool weight than the control group. The 80 g group added about 22.2 g per day and the 120 g group added about 32.8 g per day. The control group changed by -0.8 g per day.
More frequent bowel movements
People eating prunes went to the toilet more often. The 80 g group averaged 6.8 bowel movements per week and the 120 g group averaged 5.6. The control group averaged 5.4 per week.
Gut transit time unchanged
The time food took to travel through the whole gut did not change in any group after four weeks.
More wind reported
People eating prunes reported more flatulence than those drinking only water. The extra wind was small, adding about 1.3 days per week in the larger prune group compared with controls.
Bifidobacteria rose slightly
One type of gut bacteria called Bifidobacteria showed a greater increase across the prune groups than in the control group. The rise was small but similar in size to changes seen with some prebiotic fibres in other studies.
What the authors conclude
- They conclude that prunes increased stool weight and frequency in healthy people who usually go to the toilet infrequently and eat little fibre.
- They say prunes were generally well tolerated over the four weeks.
- The authors suggest prunes may offer benefits for people whose stool weight is low.
How it was done
People often eat prunes to keep their bowels working well, but scientists had not studied this much. Low stool weight and slow gut transit are linked to gut diseases, so the authors wanted to see if prunes could help.
The authors studied 120 healthy adults who normally ate little fibre and went to the toilet three to six times a week. For four weeks, participants ate either 80 g of prunes, 120 g of prunes, or no prunes, all with 300 ml of water each day. They collected stools for seven days and measured gut bacteria, gut transit time and stomach symptoms.
What it can’t tell you
- This trial lasted only four weeks, so it cannot show what happens when people eat prunes over many months or years.
- The study only included healthy adults with low fibre intake and infrequent bowel habits, so the results might not apply to everyone.
Who paid
- Funding
- Funded by Arthritis Research UK; Versus Arthritis; Department of Health (from the PubMed record).
- Authors work at
- King's College London, UK; Queen Mary University of London, UK; University of Aberdeen, UK
The paper
- Title
- The effect of prunes on stool output, gut transit time and gastrointestinal microbiota: A randomised controlled trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Lever E, Scott SM, Louis P, Emery PW, Whelan K (2019). The effect of prunes on stool output, gut transit time and gastrointestinal microbiota: A randomised controlled trial. Clinical nutrition (Edinburgh, Scotland). doi:10.1016/j.clnu.2018.01.003Free full textPubMed 29398337DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error