Prunes

Food · Fruit · Food, Typed Supps

One of the few foods with trial evidence for constipation — and it beat the fibre supplement.

Stage by stage

Three mechanisms (The fruit): Fibre, sorbitol and phenolics, all acting at once — which is why it beats fibre alone.
Osmosis (Colon): Sorbitol is poorly absorbed and draws water into the bowel.
Stimulation (Colon wall): Phenolic compounds add a mild stimulant effect on top of the bulk and water.
Bone density (Skeleton): Separate randomised evidence supports 50–100 g daily in postmenopausal women.

What the evidence supports

Relieving chronic constipation — moderate evidence. A randomised crossover trial found dried plums superior to psyllium on both stool frequency and consistency — an unusual result for a whole food against a fibre supplement, explained by three mechanisms acting at once.
Preserving bone mineral density after menopause — limited evidence. Randomised evidence supports 50–100 g/day, though trials are small and the effect on fracture rather than density is untested.

Timing

Around 50 g a day is the trial dose, best split rather than taken at once. Build up over a week to stay ahead of the sorbitol.

Time to effect

Days: Constipation effects appear quickly at the trial dose.
Months: The bone density findings, at 50–100 g daily.

Allergens

None of the fourteen major allergens. Derived from what this food is, not from a product label.

Eating patterns

Fits: Vegan, Vegetarian, Pescatarian, Halal, Kosher, Gluten-free. Depends on the product: Low-FODMAP.

Satiety

155 on the satiety index, where white bread is 100 — high. Modelled from the Holt et al. (1995) measurements.

Environmental footprint

1.1 kg CO2e and 199 litres of freshwater per kg, matched to "Other fruit" in Poore & Nemecek (2018), Science 360.

Cost band

Cheap — roughly £3 per kg, as a band midpoint rather than a price.

Key nutrients

Nutrition per 100g

Calories: 207
Protein: 2.6g
Carbohydrate: 45g
of which sugars: 31g
Fat: 0.4g
Fibre: 7.7g
Sodium: 4mg

Food vs. supplement

A randomised trial put prunes against psyllium for chronic constipation and the food won. That is rare, and the reason is mechanistic: psyllium supplies fibre, while prunes supply fibre, an osmotic agent and a stimulant simultaneously.

Kitchen tip

Start with three or four a day and build to six over a week. Going straight to the trial dose is why people give up on day two.

Common myth

“Prunes work because they’re high in fibre.” In reality: That is one of three things happening. Sorbitol draws water into the bowel osmotically, phenolic compounds mildly stimulate the bowel wall, and the fibre bulks — all at once. It is why a randomised trial found prunes outperformed psyllium, which supplies the fibre alone. About six a day is the dose that was tested.

Recipes that use it

Oat Bran with Prunes