How to treat constipation | BBC Science Focus
I spoke with BBC Science Focus about this mundane yet common complaint. At any given moment, around one in seven adults is struggling with constipation. Here is what happens, and how best to treat it initially by using lifestyle measures:
Food, broken down and stripped of its nutrients, arrives in the colon as a watery slurry. The colon’s task is exacting: it draws the water back out and shapes what remains into stool. Constipation is that process interrupted, and the interruption takes different forms. In some people the transit is normal, yet the experience is not. Stools are hard, evacuation feels difficult, the belly is swollen. In others the colon itself is sluggish. The nerves and muscles that should send coordinated waves of contraction down its length grow dysfunctional, and the waste lingers. The longer it lingers, the more water the colon takes back, and the harder and slower everything becomes. There is emerging evidence that the gut’s microbial community and its immune signaling may play a part in this dysfunction.
And then there is a third kind, one that surprises many patients. Sometimes, the muscles around the anus fail to relax when they should and tighten instead, as if the body were bracing against the very thing it is trying to do. The problem can be compounded by issues like inadequate rectal propulsive force, reduced rectal sensation, or structural abnormalities. Often, this is learned behavior, a habit of the nervous system born of ignoring the urge to defecate, or of avoiding pain.
We tend to define constipation as fewer than three bowel movements a week, but patients describe something broader: hard stools, straining, a sense of incomplete emptying, bloating, a feeling of blockage. Some go every day and are still constipated. Each patient must be considered on an individual basis when making a diagnosis of constipation.
A few tips…
Go when the body calls. When you eat, a signal travels down the gut and the colon stirs. This is the gastrocolic reflex, and it opens a window, in the morning and within about thirty minutes of meals, when the body is ready to let go. Many of us, chronically busy, ignore it. We tell the body to wait longer—and then even longer. Over time, the rectum gets less sensitive to stretching, and the urge arrives later and fainter. When you do go, keep the visit short–around five minutes—and leave the phone or reading material behind. Lingering invites prolonged straining, which can cause or exacerbate issues like hemorrhoids.
Eat fiber, but slowly if you’re not used to it. If constipation has a cornerstone remedy, it is fiber. It gives stool bulk, coaxes the lining of the gut to release water and mucus, and holds moisture in what would otherwise be hard and dry. Guidelines suggest 25 grams a day for women and 38 for men, and over 95% of US adults fall short. I usually ask my patients to aim well beyond those minimums.
Soluble fiber (including from foods like legumes, oats and barley), has the strongest evidence. Insoluble fiber (including from foods like whole grains, vegetables and fruits) adds bulk but can aggravate bloating and gas in some people. Both have their place. I ask patients to draw most of their fiber from whole plant foods first, before trying well-studied supplements like psyllium. But zeal is the enemy here. The person who goes from a diet sparse in fiber to a mountain of whole grains and raw salads in a single weekend will be bloated and ready to quit by Monday. The gut is a gradualist. Add about five grams a week and let it adjust.
Some foods deserve special focus. In clinical trials, a few ordinary foods have been shown to help with constipation. Here are some worth considering:
Kiwifruit, two to three a day, improved stool frequency, consistency and bloating. Kiwis contain an enzyme called actinidin, along with both kinds of fiber, which together increase the water in stool.
Prunes, about 100 grams a day, improved stool frequency and consistency. They contain sorbitol, fructose and pectin, which contribute osmotic and fiber-based laxative effects.
Rye bread increased stool frequency by about 0.4 bowel movements a week and sped gut transit by about 21 hours compared with white bread in one study. The trial used about seven slices a day, which is a lot, and rye’s high fructan content may worsen gas.
Flaxseed is an old folk remedy that has now been put to the test. In a trial of adults with functional constipation, 50 grams of flaxseed flour a day for four weeks raised the median number of bowel movements from two a week to seven and improved stool consistency. It’s a rich source of both soluble and insoluble fiber, plus lignans and omega-3 fats. Fifty grams is a lot of flaxseed, roughly several tablespoons of ground seed, and I wouldn’t start there. Begin with a tablespoon of ground flaxseed a day, increase gradually as you would with any fiber, and drink plenty of water as you go.
Mango has early but encouraging support. In a four-week pilot study of 36 adults with chronic constipation, eating about 300 grams of mango a day, roughly one mango, significantly improved stool frequency, consistency and shape. The study was small and was supported in part by the National Mango Board.
Figs also have promising but preliminary support. One placebo-controlled trial tested 300 grams of fig paste a day.
One caveat: I’d treat the doses in these studies as proof of principle rather than prescriptions. One mango a day is easy. Swapping white bread for rye is easy. Seven slices of rye or 300 grams of fig paste is not what I’d ask of anyone. The goal is to build more of these foods into your day, gradually, with plenty of water.
Drink water. Fiber without fluid can make matters worse. Extra water alone won’t cure constipation in someone already well hydrated, but when fiber goes up, fluid must go up with it. I also ask about the barriers to increasing fluid intake, including mobility problems, urinary incontinence, or fluid restrictions for heart or liver disease. Sometimes the obstacle is practical rather than physiological.
The matter of the angle. The modern toilet is a bit of a design failure. Sitting upright, we kink the rectum with a muscle called the puborectalis, a sling that serves us well all day by keeping us continent, but badly in the one moment we want it to relax. Raise your feet while on the toilet, so that your knees rise above your hips, and the sling loosens, straightening the path for stool to exit. You need no fancy, expensive equipment: a small stool, an orange crate, or even a stack of books will do. This mimics the squat, which opens the anorectal angle more fully in order to let stool pass.
Move most days. Active people, or those who manage at least 150 minutes of exercise a week, have about a third lower odds of constipation. Twenty to thirty minutes of walking, cycling or yoga on most days appears most protective. Exercise may not cure established constipation, but patients report feeling better and suffering less. A sedentary life is a recognized risk factor for constipation.
The things we forget to count. Some causes hide in plain sight. Many common medications slow the gut, among them opioids, anticholinergics, calcium-channel blockers, certain antidepressants and anticonvulsants, antihistamines and calcium supplements. When it’s safe, work with your gastroenterologist and other doctors to reduce, stop or substitute them. Eating too little matters as well, whether from dieting, illness or age, because it weakens the post-meal signal that prompts the colon to move.
Probiotics are an intriguing but unsettled story. Some studies suggest a modest improvement in frequency and transit time, but the evidence is mixed and current guidelines do not strongly recommend them.
When to stop waiting. Most constipation is a passing nuisance. But when it lingers, or keeps returning, it deserves a doctor’s attention, since it can point to an underlying medical condition. And never wait if you notice blood in the stool, weight loss you can’t explain, or a lasting change in your usual pattern. These can be early signs of something more serious, including colorectal cancer, now diagnosed more often in younger adults.