Prunus domestica L. · food
Evidence tier: strong
Prunes work three ways at once: they pull water into the bowel, add fibre, and contain compounds that get the gut moving. In a trial that put them head to head against psyllium, the standard fibre supplement, prunes did better. Build up gradually or they cause wind, and drink plenty of water alongside.
Three mechanisms operate simultaneously, which is the likely reason prunes outperform single mechanism fibre supplements. Sorbitol, present at roughly 14.7 g per 100 g, is a poorly absorbed sugar alcohol that draws water into the bowel lumen osmotically, softening stool. Fibre at around 6 g per 100 g, both soluble and insoluble, adds bulk and supports peristalsis. Polyphenols, principally neochlorogenic and chlorogenic acids, have documented effects on gut motility and act as substrates for the colonic microbiota. The same sorbitol content that produces the therapeutic effect also explains the gas and bloating reported when the dose is increased too quickly.
Unusually strong for a food, because the key trial is head to head against the active comparator rather than against placebo. Attaluri A, Donahoe R, Valestin J, Brown K, Rao SS. Randomised clinical trial: dried plums (prunes) vs. psyllium for constipation. Aliment Pharmacol Ther. 2011;33(7):822-8 was a crossover trial giving 50 g of prunes twice daily or an equivalent psyllium dose for three weeks each. Prunes produced significantly greater improvement in the number of complete spontaneous bowel movements and in stool consistency than psyllium, which is the standard fibre supplement prunes are usually positioned against. Supporting this, Chey SW et al. (Am J Gastroenterol, 2021) compared green kiwifruit, prunes and psyllium in chronic constipation and found kiwifruit comparable to psyllium with fewer adverse events, a result consistent with Gearry et al. (2023) and providing an evidenced alternative for anyone who does not tolerate prunes. Beating the standard supplement in a randomised crossover design justifies a strong tier, which is a grade very few items in this library earn. The honest limitations are that trial populations were modest in size and that the effect in opioid induced constipation specifically is not established and should not be assumed.
50 g twice daily, approximately 6 prunes per serving and 100 g total per day, which is the dose used in the Attaluri trial. Build up over the first week starting at around 25 g once daily. Alternative: 2 green kiwifruit daily, per Chey 2021.
Prune juice is NOT equivalent and was not what was tested; it has substantially less fibre and only the sorbitol mechanism remains. Take with a glass of water and maintain 1.5 to 2 litres of total fluid across the day. Consistent timing helps, ideally with meals, since the gastrocolic reflex is strongest after breakfast. Allow three weeks at full dose before judging, matching the trial duration. Fibre can reduce absorption of some medications taken at the same time, so separate from levothyroxine, digoxin and lithium by at least two hours. Prunes contain meaningful vitamin K, so anyone on warfarin should keep intake consistent day to day rather than fluctuating and should mention the change to their anticoagulant clinic.
Onset: ~3 days
Very safe as a food, with the caveats concerning dose escalation and the clinical context rather than the fruit. Increase gradually: going straight to 100 g a day causes gas, bloating and cramping in most people and is the main reason the intervention is abandoned. Any fibre intervention requires adequate fluid, and increasing fibre without increasing fluid can worsen constipation and, in frail or dehydrated people, raises the risk of impaction. Prunes are high in sorbitol and fructans and frequently provoke bloating and pain in irritable bowel syndrome, where they may be the wrong choice. THE MOST IMPORTANT SAFETY CONTENT IS DIAGNOSTIC RATHER THAN PHARMACOLOGICAL: a new change in bowel habit in anyone over 50, or constipation accompanied by rectal bleeding, black tarry stools, unexplained weight loss or persistent abdominal pain, requires medical investigation and must not be managed at home. Constipation with vomiting, severe abdominal pain, distension and no passage of wind suggests bowel obstruction and is an emergency. Whole dried fruit is a choking hazard for under fives and for anyone with swallowing difficulty. If psyllium is used as the comparator or alternative, it must be taken with plenty of fluid, since taken dry it can swell in the throat or oesophagus and cause choking or obstruction, a risk that matters most in frail and elderly people.
Pregnancy: safe
Breastfeeding: safe
Among the oldest and most universal dietary remedies for constipation, documented across European, Middle Eastern and Central Asian food traditions wherever plums were dried for storage. This is the rare case where the folk remedy and the trial evidence point the same way.
Active compounds: sorbitol, insoluble and soluble fibre, neochlorogenic acid, chlorogenic acid, potassium, vitamin K
Taste: Sweet, deep and caramel like, with a chewy texture. Widely acceptable, which matters for adherence in older adults.
Remedies using Prune · Browse by body system · Check it against what you take
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