Constipation Myths and Facts

When it comes to health issues, bowels are big business. Bowel movements are part of everyday life, and we notice immediately when our routine changes. Constipation, from the Latin word constipare (“to crowd together”) is something almost everyone has some experience with. In most cases, it’s an occasional annoyance that resolves quickly. For others, particularly the elderly, constipation can be a chronic condition, significantly affecting quality of life.  Depending on the question and the sample surveyed, prevalence seems to vary widely.  It’s estimate that there are 2.5 million physician visits per year in the USA, and the costs of management are estimated at about $7.5 billion annually. It’s not a trivial issue.

One of the biggest challenges in interpreting both individual patient situations, as well as the literature overall, is understanding what’s defined as “constipation”. One person’s regular routine may be another person’s constipation. From my dialogue with patients, personal definitions seem to vary. Some panic after a single missed bowel movement, while others may be unconcerned with daily (or even less frequent) movements. What’s the optimal frequency? It depends. Infants may be 3x/day. Older children may be once daily. Adults may be daily or less frequently.  The literature generally, though not consistently, defines constipation as a delay or difficulty in bowel movements ( usually less than 3 per week) lasting two weeks. Symptoms can include infrequent, painful bowel movements, straining, and lumpy or hard stools.  When these problems last for more than three months, it’s termed chronic constipation. When constipation is accompanied by other symptoms like bloating, diarrhea, and abdominal pain, it may be termed  irritable bowel syndrome (IBS).

There are multiple causes of constipation. It may be a consequence of other illnesses (e.g., high/low thyroid, diabetes, cancer, and neurological diseases like multiple sclerosis). Drugs, both prescription and over-they-counter, can also cause constipation.  Primary or idiopathic constipation is a diagnosis of exclusion, after other causes have been ruled out.  If there are no signs of a more serious underlying condition, treatments can be considered.

Many have firmly-held opinions about their colon and their bowel movements: what’s normal, and what’s not. And there are equally strong opinions about the causes of, and solutions to, constipation. But despite the ubiquity of constipation and the firmly-held opinions on treatments, there’s a sizable chasm between practice and evidence.  This is an area with crappy (sorry) data, and it’s hard to sort out what are true treatment effects. But an absence of evidence isn’t evidence of absence, so we’re challenged to make the best decisions possible, despite a disappointing evidence base. Here are some common statements I’ve encountered, and an evidence check on their veracity.

The colon is the root of all illness

Colonic dysfunction as constipation has been described as a cause of disease since at least the 16th Century BC. It’s been a recurring medical motif as long as medicine has existed, starting with ideas of internal putrefaction, and later, once germ theory arrived, became a worry about autointoxication. This theory proposed that unnamed “toxins” were being absorbed from the bowel and causing systemic disease.  Now discredited in science-based medicine, these ideas continue to manifest today, largely in the realm of CAM with its warnings to “detox”, irrigate our colon, and indulge in other ritualistic “cleansing” practices. So today the colon continues to be blamed for all manners of illness, including eczema, cancer, high blood pressure, allergies, and more. There’s no evidence  to substantiate these claims.

I need to have a bowel movement at least every “X” to avoid toxins/allergies/chronic disease/certain death

This argument is an extension of beliefs about the necessity of bowel movements to avoid systemic disease. Interestingly, over hundreds of years, there’s always been the idea that constipation is a modern disease, one of urbanization and civilization: dietary changes, the busy pace of life and a lack of exercise.  So if you don’t feel constipated, you aren’t. Bowel habits can be evaluated on their own merits. As long as they’re not painful or hard, there is no ideal frequency. In the absence of constipation, the flushing of the colon, or the use of laxatives or other purgatives is at best unnecessary, and at worst, potentially harmful.

A lack of fibre can cause constipation, and fibre supplements are effective constipation treatments

The granddaddy of fibre cereals, All Bran, appeared on the market in the 1900s as a treatment for the diagnosis of the day,  autointoxication of the colon. Since then, fibre has held a special place in the armamentarium of health professionals and CAM advocates alike: It’s not only natural, but nature’s little broom, right?

Fibre, from cereal or other foods, serves multiple purposes in the bowel. It adds bulk to the stool and can increase the frequency of bowel movements. But there is a lack of correlation between dietary fibre intake, and the risk of constipation. And in patients given fibre supplements, the response in patients with chronic constipation is erratic. Fibre, particularly bran and other insoluble fibres causes gas formation, which can limit acceptance. Soluble fibres, like psyllium (Metamucil) are better tolerated.

Studies suggest that that low fibre diets may be a a contributing factor to constipation in a subset of patients, who may  respond to higher fibre diets. Consequently, Fibre supplements may be useful in some patients with mild or occasional constipation. But in more severe cases of chronic constipation, fibre can actually aggravate symptoms,and does not appear to be an effective therapy.

Drinking more fluids can help reduce the risk of constipation

The idea that consuming more water will result in softer, easier to pass stools hasn’t been substantiated when studied in patients with chronic constipation. Studies in the elderly have also failed to reveal an association between increased fluid intake and constipation. Constipated children, randomized to consume different amounts of fluid, didn’t experience any changes in stool frequency, consistency, or ease of defecation. Unless there’s evidence of dehydration, consuming extra fluid on its own is unlikely to make any difference in cases of constipation.

Exercise can help constipation

In most patients with constipation, this statement is true. There’s an established relationship between our activity level and our bowel habits, giving us the luxury of sleeping several hours without interruption. There seems to be a relationship between exercise levels and incidence of constipation, though across several studies, it’s not clearly a causal relationship. And in cases of vigorous exercise (e.g., running) there is clearly evidence of a significant increase in activity. While it’s not possible to do a truly randomized, double-blind trial, the evidence available supports the use of  physical exercise can be helpful for modest constipation, but it does not seem to be effective for severe cases.

Stool softeners are effective
Stool softeners (e.g., docusate sodium (Colace)) are among the most popular products prescribed for the prevention or treatment of constipation. They’re often a reflex prescription that accompanies narcotic prescriptions, because constipation is a frequent side effect of narcotic drug use, mainly due to effects on transit time through the colon. Stool softeners are essentially soap, and the theory is that they make the stool easier to pass. Despite their widespread use, there’s no good evidence that docusate sodium or docusate calcium are effective for the treatment of constipation. I find it quite fascinating that docusate sodium is one of the active ingredients in Corexit, last seen being dumped in large quantities into the Gulf of Mexico to disperse the Deepwater Horizon oil spill. Presumably the evidence is better for that indication.

Natural or synthetic, the drugs don’t work

Before treating constipation, getting an understanding of symptoms, other medications, and other illnesses is important. In cases where reversible factors  have been ruled out, drug therapy may be warranted. Despite the lack of good evidence, dietary and lifestyle changes usually precede drug therapy. In cases that don’t respond or resolve on their own, medications are next. Broadly, categories of treatments include bulk-forming products, stool softeners, osmotic agents, and stimulant laxatives.  Products available are a mix of naturally-derived and synthetic products. Some of the most popular laxatives are naturally-derived. The strange smell of Senokot tablets gives a clue to its origin: They’re senna glycosides, a product of the senna plant. The naturally occuring glucosides it contains are colonic irritants, stimulating colon contraction. Metamucil is psyllium seed husks, which swell into a gelatinous mass in the stomach, carrying water and bulk to the colon. Most of the other fibre supplements are naturally-derived as well.

The other commonly used products are synthetically derived. Milk of magnesia, despite its natural sounding name, is a suspension of magnesium hydroxide.When consumed, most of the magnesium isn’t absorbed, and it pulls fluid with it (via osmotic pressure) when it’s shunted to the colon. Polyethylene glycol (PEG) works this way, as does lactulose, a non-digestible sugar. The cathartics taken before endoscopy are all osmotic agents, too.

Bisacodyl (Dulcolax) is another popular over-the-counter product. A stimulant laxative like senna, bisacodyl stimulates colon contraction.

Despite the number of products, and prevalence of constipation, the evidence base for drug treatments is weak. There’s little head-to-head evidence that has pitted on treatment against another. So we’re largely left to make inferences from poor studies on different populations. The best evidence (which is still pretty weak) exists for the osmotic agents like PEG. Some evidence exists for psyllium, but it’s underwhelming. There’s evidence for lactulose as a treatment, as well. An excellent systematic review from the Oregon Evidence-Based Practice Center summarizes the evidence base in greater detail.

Probiotics can be effective for constipation

Probiotics, covered in depth by Mark Crislip already, are live microorganisms administered with intent of a therapeutic effect. If you like yogurt that does double duty, you’ll probably see brands that include Bifidobacterium and Lactobacillus, and, depending on your national regulator, there may be vague health claims about intestinal “wellness” on the label. The idea of probiotics for constipation is at least plausible, as probiotics have the potential to disrupt the colon’s bacteria ecosystem – if only to a very limited extent, as Mark noted in his post.  For constipation, their effectiveness hasn’t been demonstrated though. A systematic review published in 2010 examined the data supporting their use in adults and children.  Five high quality trials were identified and the results were unimpressive:

Data published to date suggest that adults with constipation might benefit from ingestion of B. lactis DN-173 010, L. casei Shirota, and E. coli Nissle 1917, which were shown to increase defecation frequency and improve stool consistency. However, in some cases, even if there was a significant difference in results, their clinical relevance is unclear.

Their conclusion:

Until more data are available, we believe the use of probiotics for the treatment of constipation condition should be considered investigational.

Overall, not encouraging. And little reason to recommend their use. That’s the opinion of some regulators, too. The European Food Safety Authority has largely rejected general health claims for probiotics.

Taking laxatives continuously is dangerous and leads to tolerance and then dependence

This is a common myth, but not substantiated by fact. [PDF] As a pharmacist I see a lot of chronic laxative use – some appropriate, and some clearly inappropriate. Something that was planted in my head in pharmacy school was the warning that chronic use would lead to dependence, and a near-certain risk of constipation if their use was suddenly stopped.  The warning is primarily with the stimulant laxatives, which have been believed to affect nerve conduction and muscle damage, largely based on anecdotal evidence. Microsope examination of colon tissue in chronic laxative users reveal some differences from normal subjects. But whether these changes are caused by stimulant laxatives, or are a product of an underlying disorder, is unclear. The best evidence we have suggests that risks of of most  laxatives, when used to treat constipation, at recommended doses, is probably small.  Risks seem restricted to patients with severe symptoms on high doses of stimulant laxatives.  Notably, because laxatives are generally not even absorbed, there is no risk of them directly causing nervous system effects. Consequently, there’s no risk of a actual addiction, through there’s no question that they can be misused. Misuse beyond the treatment of constipation can be problematic, potentially leading to electrolyte disturbances.

Children are little adults

False. Constipation is children is common, and it causes distress to parents, too. I’ve spoken with parents of infants only weeks old, already set on giving their child a suppository because the “regular” bowel movement is hours late. In infants, parents often ask me about iron-free formulas, thinking the iron may be causing constipation. However iron-fortified formulas haven’t been shown to be more constipating that iron-containing formulas. So switching to an iron-free formula may have no effect, and introduce the challenge of ensuring adequate iron intake.

The most common cause of constipation in children is functional constipation – constipation without an intrinsic cause, usually caused by children deliberately delaying or avoiding bowel movements, usually due to a painful past movement. Delaying causes further constipation, and further pain with bowel movements. Functional constipation is the cause of almost all constipation in children. Constipation that’s accompanied by abdominal pain, nausea, anorexia, or vomiting needs a physician examination to rule out other causes.

Despite its frequency, constipation in children rarely lasts and generally doesn’t require medication. Which is good, because there’s little evidence to demonstrate that laxatives are effective in children. A systematic review published earlier this year summarized the evidence base. Like treatment for adults, the data are limited. Because of the lack of evidence, dietary changes, while also not well supported by evidence, should precede any drug therapy. Acute treatments should be followed with longer term strategies to prevent further episodes. While the effectiveness of fibre for the treatment of constipation in children hasn’t been demonstrated, encouraging fibre-rich fruits or vegetables as a first step may plausibly help, and have numerous other health benefits as well.


Constipation is is common condition, yet there’s little high quality evidence to guide our actions. Myths about constipation further complicate treatment strategies. In the absence of high quality evidence, it would seem most conservative to carefully evaluate each situation for potentially causal factors, and introduce the treatments backed by the best evidence only after core dietary and lifestyle factors have been implemented.

Posted in: Science and Medicine

Leave a Comment (22) ↓

22 thoughts on “Constipation Myths and Facts

  1. Anthro says:

    The woomeisters get a lot of business with this one! It’s all there–toxins, probiotics, purging, cleansing and all manner of “energy”rituals. A far bigger load of crap than the patient is trying to unload.

    I had to listen to someone with this “problem” going on about one of her “chakras” for 20 minutes yesterday. I got through it without a single eye roll. Why is that I have to be so “tolerant” of everyone’s “beliefs” when it is they who are so offensive with their medieval magic?

    In this case, though, it’s not just the woo-inclined. Any drugstore is loaded with remedies for constipation. I’ve always thought I’m okay due to a high fiber diet (lacto-ovo veggie–lots of beans and greens), but now I think it might just be one of those things and some good luck.

  2. CarolM says:

    Once a day, baby! Or else I risk a horrible bout of abdominal pain and nausea, which I used to experience periodically for years until I caught on. But yeah, like a kid I have to make time for it.

    Any evidence that the sugar-free candies with phenylalanine, with their laxative effect, could cause any rebound constipation?

    Also, we are often warned about a “change in bowel habits” as a symptom of colon cancer. That seems awfully vague. What kind of change?
    A friend told me for him it was diarrhea. What causes this, what is the connection with cancer growth exaclty.

    Fascinating subject!

  3. deus_otiosus says:

    I have Duchenne muscular dystrophy and have taken 17mg of PEG every morning since a softball-sized compaction was removed from my bowel in 2007. The reasons escape me, but I do sit half the day, use a bedpan, and my muscles suck. Your thoughts?

  4. DugganSC says:

    What, no mention of the extremely traumatizing method of mineral oil enemas?

    It’s always wonderful to go here and plug in the most recent medical advice by friends and see what comes up. Just recently, someone was recommending Align to me for a stomach upset and I was happy to read your article on probiotics before I could crumble and buy some (the stomach upset went by a few days later on its own).

  5. AlexisT says:

    My home remedy for constipated children has always been that old standby, prune juice (which I have had doctors recommend). I just googled it to see if I got any scientific evidence at all, and instead was confronted with screens of woo. I’ve been known to eat dried apricots myself, especially when pregnant–the promise of extra iron and digestive benefit was hard to resist.

    Interesting to hear that about Colace. After C-section #1 (not in the US) I did not get any. The midwife told me to take lactulose (and threatened glycerin if it didn’t work) but I figured I’d give it another day and it sorted itself out. After C-section #2, the hospital gave me Colace twice a day and sent me home with a prescription (with no fewer than 12 refills, because what I really want is a year’s supply of Colace). It took exactly the same amount of time as with #1. In both cases, I was also anemic and had iron pills on top of the narcotics.

  6. My daughter had issues with constipation and stomach ache in first grade. Our NP gave us various recommendations. The two things that seemed to work was cutting back slightly on the dairy (my daughter was a cheese fiend) and having her select a standard time after a meal to sit on the toilet. Haven’t had any problems since, but I got the idea it was a first grade thing.

    I have heard that iron in formula can constipation in infant/toddlers. In international adoption people suggest that it’s the switch from formula with no iron to formula with iron. As I recall the recommendation is to make a gradual shift by blending formulas. Hard to know if that’s real, many babies have been drinking diluted formula, kefir, fruit tea (water with some fruit boiled in it) or soy milk, so any constipation could just be the dietary change overall.

    For mild constipation, I find some exercise and a few of the yoga twisting poises are helpful.

  7. JPZ says:

    @Scott Gavura

    The Chmielewska and Szajewska (2010) review you cited reviewed five different probiotic strains. If one strain of probiotic is efficacious in one indication, it does not mean that any other probiotic will be effective as well ( Probiotic strains differ by mechanism, gut survival, replication in the gut, ecological niche and elimination. This was not a “systematic review” it was a review of five independent studies. Four out of the five studies showed improvement mostly based on NIDDK criteria of “Constipation is defined as having a bowel movement fewer than three times per week.” The one study that showed no efficacy was a children’s study using Lactobacillus GG as an adjunct to lactulose (i.e. a different study question that did not test the direct effects of probiotics). Moreover, there were no adverse effects reported among the five trials.

    “The European Food Safety Authority has largely rejected general health claims for probiotics.”

    Not so fast. EFSA rejected 170 of 180 submitted claims for insufficient information. But, the EFSA process does not define what constitutes sufficient information and communication between the review panel and the petitioner is not allowed during the review process. Only after the claim is rejected do you find out what was needed – and then the panel may change to different experts with different biases when you resubmit. The International Scientific Association for Probiotics and Prebiotics submitted their reaction as well ( This is the professional organization for scientists in this field – the industry one is Internation Probiotics Association.

    Thank you for the review, and it is an important topic. For the reasons stated, I just feel the section on probiotics could have used a little more science.

    1. Scott Gavura says:


      This was not a “systematic review” it was a review of five independent studies.

      I called it a systematic review because it was a systematic review: “Systematic review of randomised controlled trials: Probiotics for functional constipation“. The methodology notes the authors followed the Cochrane handbook for systematic reviews of interventions.

  8. JPZ says:


    “I have heard that iron in formula can constipation in infant/toddlers.”

    Children receiving infant formula tend to have more constipation in general. One mechanism is thought to be that free (not bound to a triglyceride backbone) 12-14 carbon fatty acids (e.g. palmitate from palm oil, et al.) bind to calcium and other divalent cations to form a classic soap that creates constipation. Engineered fats (e.g. betapol) reduce this problem by making it less likely that free 12-14 carbon fatty acids will be cleaved in the gut ( They are also very expensive to use in infant formula.

    I don’t think iron has been proven to cause constipation from infant formula (

  9. JPZ, Yes, you are in agreement with Scott’s article. Is it possible or unlikely that a switch from non iron to iron formula would cause constipation (temporarily, of course).

  10. CarolM “Also, we are often warned about a “change in bowel habits” as a symptom of colon cancer. That seems awfully vague. What kind of change?
    A friend told me for him it was diarrhea. What causes this, what is the connection with cancer growth exaclty.”

    I’m totally not a medical person. But here’s an anecdote. My mom was treated for uterine cancer. About a year, year and a half later she started having problems with constipation and stomach pain. Her doctor recommended more fiber, so she added metamucil, but it did not help. Eventually they found her original cancer had metastasized to the colon. The extensive tumors were creating blockages. Clearly, it was very advanced. I’m not sure how typical this is for colon cancer, symptom wise.

  11. Geekoid says:

    The duece you say!

    sorry, sorry.

    My daughter had sever constipation. TO the point they had to put her under and manually excavate the bowel. 8 pounds, btw.

    New we us mirilax and it’s very effective.

  12. JPZ says:


    Well, Scott’s article excluded iron as causitive factor without a reference. I thought I would provide that reference as well as share a more likely mechanism, i.e. we know the soaps are formed, we know the constipation goes down when the soaps are reduced, but we have not proven how that works. As a matter of fact, some infant formula companies (e.g. Danone and Nestle ex US) are adding probiotics or prebiotics to infant formula to help reduce constipation, and these formulas passed regulatory approval in many countries. I forgot about that little factoid in my reply to Scott.

    I am not aware of any research on iron causing constipation when switching formulas. Anecdotally, pediatricians have told me that switching formulas (cow’s milk to soy or partially hydrolyzed) is a technique they use for colic management – colic lasts about 1-3 weeks and switching formula takes 2-3 weeks, voila colic “cured” by what might or might not be a placebo effect/delaying tactic. I am remembering those numbers off the top of my head, so don’t quote me on those being exact. Since the same brand of formula +/- iron should have nearly identical composition, this may not apply. A pediatrician would be much more enlightening drawing upon their clinical experience for an answer.

  13. JPZ, “I thought I would provide that reference as well as share a more likely mechanism, i.e. we know the soaps are formed, we know the constipation goes down when the soaps are reduced, but we have not proven how that works.”

    Yes, Thanks for that reference and the interesting explanation!

  14. JPZ says:

    @Scott Gavura

    Then it misused the Cochrane criteria. By classifying them all as “probiotics,” it equivocated treatments as diverse as aspirin, acetominophen and morphine for different kinds of pain relief, e.g. for a femoral crush injury there is little evidence that this class of compounds has any efficacy. Each species has a distinct metabolism and mechanism of action, which was part of EFSAs rejection of claims in favor of more details about the various species for which claims were submitted. I provided an expert reference for my assertion in my first link. I maintain, this is a review of five independent studies – four of which found efficacy and the fifth didn’t test probiotic efficacy.

    I sympathize that you found their terminology deceptive. I too have been mislead by reviews outside my field of expertise. It is my intent to clarify the actual science.

  15. JPZ, sorry, I think everything I type sounds curt. It’s not intended, just tired today.

  16. JPZ says:


    It didn’t sound curt at all. You focused in on your next concern after reading my reply, we tend to be focused when we get one answer we wanted and immediately look for another. It is called curiousity! :)

  17. kathy says:

    I guess I’m blessed that I seldom get constipated … it’s pretty uncomfortable when I occasionally do.

    One “remedy” that’s not been mentioned … actually its more of a preventative … is routine. For me in the morning, it’s to sit down with a mug of tea and play computer games! After 5 minutes I’m ready to “go”. Vary the routine, e.g. if I wake late, or if I go on a camping trip where I don’t have my pc along, and my system doesn’t know what’s happening. It can be re-programmed of course, it’s not the law of the Medes and the Persians, which cannot be changed. But a change in routine generally gets things in a twist for a few days, till the new routine takes over.

    Just a suggestion.

  18. kortikosteroid says:


    “Any evidence that the sugar-free candies with phenylalanine, with their laxative effect, could cause any rebound constipation?”

    as far as i know, it’s not the aspartame that carries the laxative effects of sugar free candies, but the sugar alcoholes they contain. sugar alcoholes basically work like dietary fibers- they aren’t broken down in the small intestine, and they absorb water. but they also tend to create gas and some discomfort, as bacteria in the large intestine feast on them later on.

  19. JPZ says:

    @Scott Gavura

    I presented science-based evidence (IMHO) refuting both lines of argumentation supporting your dismissal of probiotics as an effective treatment for constipation (the non-systematic review and the true basis of the EFSA rejection of probiotic-related claims). I can provide more, and it will not be derived from some woo website. I would happily engage in a scientific discussion to examine the strengths and faults of the published research, but I think it does readers a disservice to dispute the efficacy of a product using questionable (questioned by me to be specific) scientific evidence.

  20. Robin says:

    Great post! My sweetie has chronic constipation issues that may have (probably) resulted in anal fissure and subsequent surgery. Not fun!

    He diligently does all of the things recommended, and it was helpful to read the run down on the evidence for each. He feels adding beans and vegetables to his diet, exercising, and Colace have helped the most, but it’s interesting that the evidence is shaky to the third. You only briefly mentioned dietary fiber (vs. supplemented) but that I was the one I really pushed because his diet was pretty awful.

    Probiotics seem so implausible to me because of stomach acid. I recall a big fight in the medical world about h. pylori and uclers – based on the notion that it would be impossible for bacteria to survive in the stomach. Obviously some can, but all of the probiotic strains? Wouldn’t they be more effectively…inserted? Unless the little bugs are absorbed in the esophagus on the way down.

  21. JPZ says:


    Encapsulation and coating technologies can help with survival, but they also are feeding 5-10 billion organisms in a single dose. Some will get through intact anyways and then they can “grow back” once they reach the appropriate ecological niche in the gut. Survival of the organisms in the gut has been confirmed both using classic microbiological methods and genetic markers (FISH method).

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