If a bowl of bran cereal and "drink more water" haven't solved your constipation, the kitchen still has more to offer. Researchers have now tested several everyday foods and drinks in proper trials, sometimes directly against fiber supplements.
In 2025, the British Dietetic Association used that research to publish what its authors describe as the first comprehensive evidence-based dietary guidelines for chronic constipation. Here's how the main food-first options compare.
What the new guidelines covered
The guideline team ran four systematic reviews covering 75 randomized controlled trials and produced 59 recommendation statements. For foods, there were statements on kiwifruit, prunes and rye bread. For drinks, they addressed high mineral-containing water.
The rest covered supplements, including fiber supplements, probiotics, magnesium oxide, senna and kiwifruit supplements. No recommendations were made for whole-diet approaches because the evidence was lacking (Dimidi et al., 2025).
It's worth knowing the limits. Most statements rested on low or very low quality evidence, and only 8 of the 59 were based on moderate-quality evidence.
How the options compare
Kiwifruit
The evidence: A 2024 meta-analysis of foods, drinks and diets for chronic constipation included 7 studies on kiwifruit, more than for any other food. Fruits led to more frequent bowel movements than psyllium, an extra 0.36 a week, and kiwifruit on its own showed the same difference (van der Schoot et al., 2024).
In a partially randomized US trial, 79 adults with chronic constipation, 87% of them women, ate 2 green kiwifruits a day, 100 grams of prunes a day, or took 12 grams of psyllium a day for four weeks. All three increased complete bowel movements. Kiwifruit also improved bloating scores, had the fewest side effects, and left the fewest people dissatisfied (Chey et al., 2021).
In practice: two green kiwifruits a day, eaten however you like. They're easy to add to breakfast or have as a snack.
Prunes
The evidence: In a crossover trial of 40 adults with constipation, 37 of them women, prunes (50 grams twice a day) were compared with psyllium (11 grams twice a day), each providing 6 grams of fiber a day, for three weeks each. Prunes led to more complete spontaneous bowel movements and better stool consistency than psyllium. Both were rated equally palatable and were well tolerated (Attaluri et al., 2011).
The pooled data are less clear-cut. The 2024 meta-analysis found no difference between prunes and psyllium for stool frequency (van der Schoot et al., 2024).
In practice: a reasonable option if you like them. Start with a smaller portion and build up over a week or two.
Rye bread
The evidence: In the 2024 meta-analysis, rye bread led to more frequent bowel movements than white bread, an extra 0.43 a week, based on 48 participants (van der Schoot et al., 2024).
In practice: swapping white toast for a fiber-rich rye bread is a simple change. The evidence base is small, so treat it as one helpful piece rather than a complete fix.
Mineral-rich water
The evidence: In a double-blind trial, 244 women aged 18 to 60 with functional constipation drank 1.5 liters of water a day for four weeks. In one group, 1 liter of that was a natural mineral water rich in magnesium sulfate. By week two, constipation had improved in 37.5% of that group, compared with 21.1% of women drinking only low-mineral water. Responses tracked with magnesium sulfate content (Dupont et al., 2014).
In the pooled analysis, involving 539 participants, high-mineral water led to a better treatment response than low-mineral water, with a relative risk of 1.47 (van der Schoot et al., 2024).
In practice: check the label for magnesium and sulfate content. If you have kidney disease or have been told to limit magnesium, ask your doctor first.
Where psyllium still fits
None of this makes fiber supplements obsolete. The guidelines addressed fiber supplements in 15 separate statements (Dimidi et al., 2025), and psyllium also increased complete bowel movements in the US kiwifruit trial. It simply caused more side effects than kiwifruit in that study (Chey et al., 2021). Food-first options are an alternative worth trying, not a replacement.
