According to the British Dietetic Association (BDA), evidence-based strategies and clinical guidelines emphasize a simple, often high-fiber-containing diet. Further, based on the latest research published in 2025-2026, effective evidence-based dietary management of chronic constipation focuses on increasing soluble fiber Psyllium (ispaghula) is strongly recommended to increase stool frequency and consistency, with better evidence than insoluble fiber (e.g., wheat bran).
The Specific Foods recommended are Kiwifruits 2–3 daily (with or without skin), which significantly improve stool frequency and consistency, and prunes, which are dried plums, specifically from the European plum (Prunus domestica), known for their chewy texture, sweet-savory flavor, and high nutritional value. They are popular for aiding digestion due to their high fiber and sorbitol content, which helps improve bowel function. Prunes are a nutrient-dense “super food” rich in potassium, vitamin K, and antioxidants, supporting bone health, heart health, and energy.
Also, rye bread 6–8 slices per day, has shown effectiveness. Increased fluid intake is vital. High-magnesium or sulfate-rich mineral waters show promising results. The probiotics and fermented foods, certain strains, such as B. lactis and Bacillus coagulans, are supported for improving gut transit and consistency. The National Institute of Health (NIH) guidelines recommend the SMART Constipation Diet, which is a new, comprehensive model focusing on Sensory (taste/palatability), Motor (motility/fiber), Acid (bile acid/fat), and Reflex Tailored approaches to maximize dietary impact.
Though fiber is foundational, it may be less effective in patients with severe slow-transit constipation or pelvic floor dysfunction. Besides it is advised life style modifications include proper toilet training and gradual, rather than abrupt, increases in fiber (to avoid bloating/gas).
Current evidence
This review comprehensively examines the current evidence and clinical guidelines on the dietary management of chronic constipation. Several randomized controlled trials (RCTs) have investigated the effect of dietary supplements, foods and drinks in chronic constipation. To summarize, the systematic reviews and meta-analyses of these trials have demonstrated that psyllium supplements, specific probiotic supplements, magnesium oxide supplements, kiwifruits, prunes, rye bread, and high mineral water content may be effective in the management of constipation.
However, despite the plethora of evidence, current clinical guidelines only offer a limited number of dietary recommendations. The most commonly recommended dietary strategy in clinical guidelines is dietary fiber, followed by senna supplements and psyllium supplements.
The least commonly recommended dietary strategies are magnesium oxide, Chinese herbal supplements, prunes and high mineral-content water. Several evidence-based dietary strategies are omitted by current clinical guidelines (e.g. kiwifruits), while some strategies that are recommended are not always supported by evidence (e.g. insoluble fiber supplement).
Dietary recommendations in clinical guidelines can also be ambiguous, lacking outcome-specific recommendations and information for appropriate implementation. Future research is needed to assess currently under-investigated dietary approaches that are nevertheless commonly recommended, and future clinical guidelines should include dietary recommendations supported by available evidence.
Significant outcome
Importantly, while some fibres do improve some symptoms, they may also exacerbate others. For instance, although inulin-type fructans did soften stool consistency, they also increased the severity of flatulence, compared to the control. This is an expected outcome, given that inulin-type fructans are highly fermentable fibres, resulting in colonic gas production by the gut microbiota. Taken together, the evidence supports the use of psyllium supplements at doses exceeding 10 g per day for at least 4 weeks for the management of chronic constipation. A gradual dose increase is often recommended to minimise and closely monitor potential side effects, such as flatulence.
Magnesium oxide supplements
Magnesium oxide is converted to magnesium chloride in the stomach due to its acidic environment. It is further converted into magnesium bicarbonate by sodium bicarbonate in the duodenum, subsequently forming magnesium carbonate. Both magnesium bicarbonate and magnesium carbonate act as osmotic agents, promoting water retention in the gut lumen.
This may result in softer stools and increased stool bulk, with the latter leading to mechanical stimulation of the gut wall and increased gut motility. Indeed, research showed that magnesium oxide supplements significantly reduced gut transit time from baseline, whereas no difference was found in the control group; however, no direct comparison between the two groups was reported at the fourth week.
A systematic review and meta-analysis involving 94 healthy participants with chronic constipation showed that 68 % of those receiving magnesium oxide supplements responded to the treatment, compared to only 19 % in the control group. Magnesium oxide supplements significantly increased stool frequency, complete spontaneous bowel movements, and softened stool consistency, compared to control. They also reduced global gut symptoms, as well as straining and incomplete evacuation.
Therefore, magnesium oxide supplements should be initiated, when clinically appropriate, at a lower dose of 0·5 g per day and increased gradually based on symptom response and tolerance. However, dose should not surpass 1·5 g per day to avoid hypermagnesemia.
Probiotic and symbiotic supplements
Probiotics are live microorganisms that, when administered in adequate amounts, confer healthy benefit to the host. Some probiotics modulate the composition of the gut microbiota and their metabolite production, and also interact with the immune and enteric nervous system, the latter being the primary regulator of gut motility.
Therefore, in a few cases, the probiotics may improve constipation symptoms. A survey of 934 people with self-reported constipation showed that 37 % have previously or are currently using probiotics for their gut health. This suggests that people with chronic constipation commonly choose probiotics as a potential management option for their symptoms. However, the majority of general practitioners and gastrointestinal specialists do not recommend probiotics for constipation and, importantly, do not believe they have been tested in research studies in constipation.
In fact, believing that probiotics have been tested in research for their effect on constipation was a significant predictor for probiotic use by people with constipation. This highlights not only the influence of perceived research evidence in choosing probiotics as a treatment for constipation but also the fact that it is imperative to appropriately communicate and educate the public and clinicians on the current evidence and its strength in this area.
Several systematic reviews have investigated the effect of probiotics in chronic constipation. Improved key symptoms of constipation, compared to placebo. Recently, an updated systematic review and meta-analysis showed that overall, probiotics significantly increased response to treatment, compared to placebo.
Role of Synbiotics
Synbiotics are a mixture comprising live microorganisms and substrate(s) selectively utilised by host microorganisms that confers a well-being benefit on the host. A systematic review and meta-analysis identified the role of synbiotic supplements made of various probiotics in chronic constipation. Synbiotic supplements had no impact on stool frequency and consistency and global symptoms, compared to placebo, and are therefore not considered to be effective in constipation. The action of other supplements and related research with significant results will be discussed in the coming issue. (To be concluded).
