A laxative is any substance that helps you have a bowel movement when you’re constipated. Laxatives work through several different mechanisms: some soften the stool by pulling water into it, others stimulate the muscles of your colon to push things along, and some do both. They come in over-the-counter pills, powders, liquids, and suppositories, and they’re one of the most commonly used categories of medication.
How Different Types of Laxatives Work
Not all laxatives do the same thing inside your body. They fall into several categories based on how they produce a bowel movement, and choosing the right type depends on what’s causing your constipation and how quickly you need relief.
Bulk-forming laxatives are the closest to how your body naturally moves stool. They contain fiber (like psyllium husk) that absorbs water in your intestines, making the stool larger, heavier, and softer. The added bulk signals your colon to contract and push things forward. These are the gentlest option and typically take 12 to 72 hours to work.
Osmotic laxatives are substances your body can’t absorb well, so they stay in the intestine and draw water into the bowel. Polyethylene glycol (MiraLAX) and magnesium hydroxide (milk of magnesia) are common examples. By flooding the colon with extra fluid, they soften the stool and make it easier to pass. Most people see results within 1 to 3 days.
Stimulant laxatives take a more aggressive approach. Ingredients like bisacodyl and senna directly activate the nerve endings in your colon wall, triggering stronger muscle contractions that push stool through faster. They also reduce how much water your colon absorbs, keeping the stool wet. Stimulants typically produce a bowel movement within 6 to 12 hours, making them a popular choice for faster relief.
Stool softeners lower the surface tension of the stool so that water and fats can penetrate it more easily. Docusate sodium (Colace) is the most familiar example. These don’t stimulate your colon muscles at all. They simply make what’s already there softer and easier to pass, which is why they’re often recommended after surgery or childbirth when straining is a concern.
Lubricant laxatives like mineral oil coat the stool with a slippery layer so it slides through the intestine with less friction. They’re sometimes used as enemas for more immediate relief.
Foods That Work as Natural Laxatives
Before reaching for a pill, many people find relief through diet. Fiber is the key ingredient here, and it comes in two forms. Insoluble fiber, found in fruit and vegetable skins, leafy greens, nuts, and popcorn, adds bulk to stool and speeds its passage. Soluble fiber, found in oatmeal, bananas, apples, and whole grains, absorbs water and forms a gel that softens stool. Many foods contain both: a potato, for instance, has soluble fiber inside and insoluble fiber in the skin.
Prunes deserve their reputation. Beyond fiber, they’re rich in sorbitol, a sugar alcohol that your body can’t break down during digestion. When sorbitol reaches the colon, it draws water in and triggers a bowel movement, functioning much like an osmotic laxative. Apple juice contains sorbitol too, though in smaller amounts. Hot caffeinated beverages like coffee and tea can also get things moving by stimulating the colon muscles and speeding up digestive motility.
Side Effects and Risks
Short-term, occasional use of most laxatives is well tolerated. The most common side effects are bloating, gas, cramping, and loose stools. Osmotic laxatives can sometimes cause excess gas and abdominal discomfort as they draw fluid into the bowel. Stimulant laxatives may produce stronger cramps because they’re actively forcing your colon to contract.
The bigger concern is what happens with heavy or prolonged misuse. Frequent laxative use can cause significant losses of water and electrolytes, particularly potassium and sodium. These minerals regulate nerve impulses and muscle function throughout your body, including your heart. Severe imbalances can lead to muscle weakness, numbness, irregular heartbeat, and in extreme cases, cardiac arrest. This is especially relevant in the context of eating disorders, where laxative misuse is common.
There’s also the concept of “lazy bowel,” where chronic use, particularly of stimulant laxatives, may weaken normal bowel function over time, leading to worsening constipation and dependence. However, the medical picture here is more nuanced than the common fear suggests. A review of the clinical evidence found no convincing proof that chronic stimulant laxative use causes permanent structural damage to the nerves or muscles of the colon. The authors concluded that the risks of laxative use have been overemphasized and that stimulant laxatives can be used long-term when gentler options aren’t sufficient, ideally at the lowest effective dose.
Laxative Use in Older Adults
Constipation becomes more common with age due to slower digestive motility, less physical activity, and medications that affect the gut. For older adults, the first-line recommendations are typically polyethylene glycol or senna-based laxatives combined with a bulk-forming agent. Both have been studied specifically in geriatric populations and shown to be safe and effective.
In one long-term trial, polyethylene glycol helped 61% of elderly participants achieve regular bowel movements compared to just 22% on placebo. Sorbitol-based laxatives have also performed well in older adults, matching the effectiveness of lactulose while costing less and producing fewer side effects. For older adults dealing with chronic constipation that doesn’t respond to over-the-counter options, prescription medications that increase fluid secretion in the colon have shown significant improvement, boosting weekly bowel movements from roughly 1 to 2 per week up to 4 to 5.
Choosing the Right Type
If you’re dealing with occasional constipation, a bulk-forming laxative or increased dietary fiber is the gentlest starting point. These work with your body’s natural processes and carry the fewest side effects, though they require patience and adequate water intake to work properly.
Osmotic laxatives are a reasonable next step if fiber alone isn’t enough. They’re effective, widely available, and safe for longer use. Stool softeners are most useful in specific situations where you want to prevent straining rather than treat active constipation.
Stimulant laxatives are best reserved for when gentler options haven’t worked. They’re faster and more powerful, but they’re also more likely to cause cramping. Using them occasionally is fine for most people, but relying on them daily without guidance can create a cycle where your colon becomes less responsive to natural signals. If you find yourself needing laxatives regularly for more than a couple of weeks, that’s worth investigating, since chronic constipation can signal dietary issues, medication side effects, or underlying conditions that a laxative alone won’t fix.