Is Prune Juice Good for You? Sugar, Sorbitol and Potassium

Prune juice is a fruit juice with sorbitol in it, a sugar alcohol the gut absorbs slowly. Per 100 g it carries 14.4 g of sugars, about 6 g of sorbitol, 210 mg of potassium, 57 kcal and only trace fibre, so a small 150 ml glass is roughly 22 g of free sugars against the NHS limit of 30 g a day for adults, and the NHS asks everyone to keep fruit juice to 150 ml a day.^{1, 2, 3} Whether that is "good for you" depends on what you want from it. On constipation it has one placebo-controlled trial, 54 g a day for eight weeks, and whole prunes have two trials against psyllium and an authorised claim at 100 g a day; does prune juice help constipation covers that evidence.^{4, 5} This page covers what is in the glass, why it can make you feel odd, whether it stops working, who should go carefully and how to use a concentrate. For the fibre the juice does not supply, the Wellgard fibre guide sets out the 30 g a day target.

What does prune juice contain, and how does it compare with prunes?

The UK reference figures come from McCance and Widdowson's dataset, CoFID, and the sorbitol figures from the 2001 review of prune composition.^{1, 2}

Juicing filters out the fibre and keeps the sugars, the sorbitol and the minerals, so a glass of prune juice is closer to any other fruit juice than to a handful of prunes. The things prunes are studied for beyond the bowel, bone density in post-menopausal women at 50 g a day for a year, for instance, were tested with the fruit, not the juice.⁶ Prune juice "from concentrate" on a carton is juice that was concentrated for transport and reconstituted with water to its original strength; it should match pressed juice on the label.

Is the sugar in prune juice bad for you?

It is the same sugar as in any fruit juice, and the NHS treats it the same way: the sugars in fruit juice count as free sugars because juicing releases them from the fruit's cells, adults should have no more than 30 g of free sugars a day, and unsweetened juice and smoothies together should be kept to 150 ml a day.³ A 150 ml glass of prune juice carries about 22 g, so a daily glass uses most of that allowance, and a 250 ml tumbler exceeds it on its own. "No added sugar" on a prune juice or concentrate label describes added sugar; the fruit's own sugars remain, and they are what the free-sugars figure counts. For someone with diabetes a glass of prune juice carries about 22 g of sugars to count like any other juice and to discuss with their diabetes team; whole prunes possibly behave differently, since the composition review suggests their fibre and sorbitol slow the rise in blood glucose.²

What is sorbitol, and why do you feel odd or windy after prune juice?

Sorbitol is a sugar alcohol that the small intestine absorbs poorly. What is not absorbed draws water into the bowel, and what reaches the colon is fermented by bacteria, producing gas. The trial authors suggest this may explain the effect they measured, and it is behind the side effects people describe: gurgling, cramps, wind, a sudden urge and, past your personal threshold, loose stools.² The threshold varies from person to person and with the amount, which is why a glass that does nothing for one person sends another running. Sorbitol is also a FODMAP, the "P" for polyol, and the NHS advice for IBS with diarrhoea is to cut down on sorbitol, so people with IBS who react to sugar-free sweets and chewing gum should expect to react to prune juice too.⁷ If prune juice has given you diarrhoea, the fix is simple: stop, drink water, and if you try it again use a smaller glass; it passes within a day, and diarrhoea that does not settle is a GP matter rather than a prune one.

Does prune juice stop working if you drink it every day?

No trial has found that it does, and the idea seems to be borrowed from stimulant laxatives, which are a different thing. In the eight-week trial, hard, lumpy stools were less common than on placebo from week three, normal stools more common from week three, and a normal consistency (type 4 on the Bristol scale) more common from week seven.⁴ What does change is you: if prune juice "stops working", the usual reasons are that the constipation has another cause (a new medicine, a slower bowel, a diet with too little in it to pass), that fluid has dropped, or that the backlog has built past what a glass of juice can shift; our constipation guide goes through those causes, and the NHS says regular constipation is itself a reason to see a GP.⁸

Is it safe to drink prune juice every day, and who should be careful?

For most adults a small glass a day is fine within the 150 ml juice limit, and the eight-week trial reported no adverse events or changes in liver or kidney blood tests.^{3, 4} Four groups should go carefully. People with diabetes, for the sugars above. People with IBS, especially IBS with diarrhoea, for the sorbitol. People with kidney disease, because a 150 ml glass carries about 340 mg of potassium by the UK food tables and NHS kidney-diet advice is that a dietitian sets how much potassium you should have; the same caution applies to anyone taking potassium-sparing medicines, who should ask their GP first.⁹ And children: the NHS gives age-specific advice for constipated babies and children, a constipated baby is a health visitor or GP conversation, and this page gives no juice dose for a child.¹⁰ In pregnancy and breastfeeding, or if you take medication, ask your GP or midwife first, as the concentrate's label advises. "What organ are prunes good for?" is a question about the fruit: the bowel evidence is above, and the bone trial used 50 g of prunes a day; no trial has looked at prune juice and belly fat, and no juice reduces fat anywhere in particular.⁶

How do you use a prune juice concentrate?

A concentrate is prune juice with most of its water removed, sold in a small bottle and diluted at home. A typical serving is 30 ml of concentrate stirred into a glass of water once a day; it carries the fruit's own sugars with no added sugar, and its potassium contributes to normal muscle function. Labels warn that it may have a laxative effect and that it is not for children under 12, and an opened bottle is kept in the fridge and used within the period stated. The register's bowel-function claim belongs to 100 g of dried plums, and the sugar, sorbitol, IBS, diabetes and potassium notes above apply to a concentrate too.⁵ No trial has compared a concentrate with pressed juice or with whole prunes, so "is concentrate as good as juice?" has no trial answer. Measure it rather than pouring, use cold or room-temperature water (or stir it into yoghurt or a smoothie), and never drink it neat from the bottle.

Frequently asked questions

Can you make prune juice from dried prunes?

Yes: soak or stew prunes in water and blend. Strictly that is a purée, not a juice, and it keeps the fruit's fibre.²

Do prunes or prune juice need to be refrigerated?

Dried prunes keep in a cupboard. Opened juice goes in the fridge and is used within the days the carton states; an opened concentrate is refrigerated and, for the product above, used within 16 days.

Is two prunes a day too much?

No. Two prunes are about 20 g, roughly 7 g of sugars and 1 g of fibre; the bowel trials used 80 to 120 g a day and the bone trial 50 g.^{1, 6, 11}

What is the healthiest prune juice to drink?

One that is 100% prune juice with nothing added. Beyond that the differences are small, and the healthiest amount is the 150 ml the NHS allows for any juice.³

Is "light" prune juice as effective as regular?

No trial has tested a reduced-sugar prune juice, and labels rarely state how much sorbitol survives the process.

Sources

1. Public Health England. McCance and Widdowson's Composition of Foods Integrated Dataset (CoFID), 2021. gov.uk.
2. Stacewicz-Sapuntzakis M, et al. Chemical composition and potential health effects of prunes: a functional food? Critical Reviews in Food Science and Nutrition, 2001. PubMed 11401245.
3. NHS. Sugar: the facts. nhs.uk.
4. Koyama T, et al. Prune juice containing sorbitol, pectin, and polyphenol ameliorates subjective complaints and hard feces while normalizing stool in chronic constipation: a randomized placebo-controlled trial. American Journal of Gastroenterology, 2022. PubMed 35971232.
5. Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register. gov.uk.
6. De Souza MJ, et al. Prunes preserve hip bone mineral density in a 12-month randomized controlled trial in postmenopausal women: the Prune Study. American Journal of Clinical Nutrition, 2022. PubMed 35798020.
7. NHS. Irritable bowel syndrome (IBS): diet, lifestyle and medicines. nhs.uk.
8. NHS. Constipation. nhs.uk.
9. NHS. Chronic kidney disease: living with. nhs.uk.
10. NHS. Constipation in children. nhs.uk.
11. Lever E, et al. The effect of prunes on stool output, gut transit time and gastrointestinal microbiota: a randomised controlled trial. Clinical Nutrition, 2019. PubMed 29398337.