The short version
The 2026 British Dietetic Association chronic constipation guidelines reviewed 75 trials and replaced generic "eat more fiber" advice with five specific interventions: kiwifruit (2-3 daily), psyllium (5-10g daily with water), magnesium oxide (0.5-1.5g daily), rye bread, and mineral-rich water (over 1500 mg/L magnesium). Start with kiwifruit. Stack the others if needed.
Before you start
Rule out red flags first. See a clinician if your constipation started after age 50, came on suddenly, or is accompanied by blood in stool, unintentional weight loss, or severe pain. For everyone else, the sequence below is the evidence-backed dietary first line. Each step has a 4-week trial window. Move to the next only if the current intervention does not produce at least 50 percent symptom improvement. Track bowel movement frequency, stool consistency (Bristol chart), and straining severity on a 1-10 scale across each 4-week window.
Step 1 - Start with kiwifruit (2-3 per day for 4 weeks)
Eat 2-3 whole kiwifruit daily, skin on if tolerable (roughened by rubbing). Green (Actinidia deliciosa) or gold (Actinidia chinensis) both work; gold is less acidic. Kiwifruit outperformed psyllium and prunes head-to-head in a 2021 randomized trial[2]. The combination of soluble fiber, actinidin enzyme, and raphides stimulates both stool formation and transit. Tolerability is better than psyllium or prunes; less bloating, less gas. Cost is higher ($0.50-1 per fruit) than psyllium, but for many people kiwifruit alone solves the problem. Give it 4 weeks before concluding it is not working; some benefit shows within a week but full effect takes 3-4 weeks as your gut adapts.
Step 2 - Add psyllium if kiwifruit alone is not enough
Add 5-10 grams psyllium husk daily, taken with at least 250 ml (one full glass) of water per dose. Psyllium is the first-line fiber supplement in the 2026 BDA guidelines[1]. Soluble fiber that retains water, softens stool, and modestly speeds transit. The water is essential; insufficient water makes psyllium actively worse. Split across 2-3 doses throughout the day rather than a single large dose. Effect builds over 2-4 weeks. If you experience gas or bloating in the first week, reduce to 3-5 grams and ramp up gradually; the microbiome adapts within 2 weeks for most people. Psyllium pairs well with kiwifruit; do not treat them as alternatives unless kiwifruit alone is fully sufficient. Apps like Aloe AI that log meal composition alongside bowel movement frequency help isolate which intervention produced which response when you stack two or three.
Step 3 - Stack magnesium oxide or mineral water for stubborn cases
If kiwifruit plus psyllium does not resolve it after 4 weeks, add magnesium oxide at 0.5 to 1.5 grams elemental magnesium daily[1]. Magnesium oxide is intentionally the laxative form (see how to choose the right magnesium supplement) with poor absorption that draws water into the colon via osmosis. Start at 0.5 grams; increase by 0.25 grams every 3 days if needed. Stop if stools become too loose. Alternative: mineral-rich water with over 1500 mg/L magnesium (several European bottled brands, including San Pellegrino, Gerolsteiner, Vichy Catalan, Adelholzener) provides a milder laxative effect through the same mechanism. Rye bread (2 slices daily) is a third option from the guidelines; its arabinoxylan fiber has specific constipation-relieving effects distinct from wheat bran.
What to do with the results
If a 4-week trial at a given step resolves symptoms to a satisfactory level (stool frequency 3+ per week, type 3-4 on Bristol, minimal straining), maintain the approach long-term. Do not escalate unnecessarily. If the trial produces partial but incomplete benefit, stack the next step on top rather than replacing it. Many people end up on kiwifruit plus psyllium daily as a sustainable baseline. If nothing in the sequence produces improvement after 12 weeks total of trying, see a GI clinician. Subtypes like slow-transit constipation, pelvic floor dysfunction, and medication-induced constipation need different approaches that the BDA dietary guidelines do not cover.
When to see a professional
Beyond the initial red flags, persistent inability to respond to the dietary interventions after 12 weeks warrants specialist workup. Anorectal manometry can identify pelvic floor dyssynergia, a common cause that dietary changes cannot fix. Gastric-colonic transit studies identify slow-transit constipation, which often needs prokinetic medications. For constipation that starts or worsens with a new medication, review the medication list with your clinician; many common drugs (opioids, calcium channel blockers, iron supplements, some antidepressants) cause constipation as a side effect that needs direct management.
