We’ve all heard it: “Just drink more water.” It’s one of the most common pieces of advice for constipation, but how much truth is there to it? The short answer: Yes, drinking water can help when you’re constipated — but usually only if you’re already a bit dehydrated or if you pair increased water intake with increased fiber intake.
When you’re low on fluids, stool can become dry, hardened, and difficult to pass. And a large study of dietary data showed that the more liquid you get from what you drink and eat, the less likely you are to be constipated.
Here’s how hydration and digestion are connected, and why your water bottle is truly your gut’s best friend.
If you’ve ever noticed that constipation feels worse when you haven’t been drinking enough fluids, that’s not a coincidence.
The large intestine, also known as the colon, plays a critical role in fluid balance. After your small intestine absorbs nutrients from food, what remains moves into your colon, where water is reabsorbed back into your body and indigestible material is shaped into stool.
But when you’re dehydrated, your colon shifts into conservation mode, pulling even more water from stool as it passes through, according to Rabia de Latour, MD, a therapeutic endoscopist and gastroenterologist who is an assistant professor of medicine at NYU Grossman School of Medicine in New York City and an Everyday Health medical reviewer.
“It’s the water regulator in your body. When you’re dehydrated — because you ran a marathon or you exercised and didn’t drink enough water — one of the first things it will do is try to steal some water back from stool,” Dr. de Latour says. “So if somebody’s severely dehydrated and the colon absorbs a lot of water, [stool] can become dry and hard like rabbit pellets.”
“Staying hydrated is so important to have easy bowel movements because it helps to keep things moving,” says Amanda Sauceda, RD, a registered dietitian in Long Beach, California, focused on gut health. “If you’re always dehydrated, that will show up with harder stools or you’ll find yourself pooping less often,” she says.
Water works best when paired with sufficient dietary fiber, according to Amy Burkhart, MD, RD, an integrative medicine physician and registered dietitian in Napa, California, where she specializes in treating patients with digestive health issues.
There are two main types of
fiber: soluble and insoluble.
- Soluble fiber, found in foods like oats, apples, and beans, dissolves in water and forms a gel-like substance that softens stool. “Increasing your soluble fiber intake can help you go more often and make your stool softer and easier to pass. A bonus action of soluble fiber is that it serves as food for the gut bacteria,” Dr. Burkhart says.
- Insoluble fiber, found in whole grains and many vegetables, adds bulk and helps stool move through the colon more efficiently. “It’s a bit different and does not form a gel but it does help give shape and structure to your poop,” Sauceda says.
You can think of fiber like a sponge. It needs water to swell, soften, and do its job properly.
That’s why increasing fiber intake without increasing water can actually worsen constipation, de Latour warns. Supplements like psyllium husk or high-fiber cereals draw fluid into stool, but if there isn’t enough fluid available, stool can become even harder.
Increase your fiber intake slowly, Burkhart advises. “It’s very normal for someone to experience gas and bloating when increasing their fiber intake, but it is typically very tolerable as long as they start low and increase fiber intake slowly,” she says.
You should be aiming for 25 to 30 grams (g) of
fiber per day. Most people only get about half that amount.
Many people swear by a warm cup of water or tea first thing in the morning to “get things moving,” but there are few scientific studies to back this claim.
“I do have patients tell me that warm liquids improve their constipation,” Burkhart says. “It may be through improved blood flow to the gut, increasing movement, or simply mental relaxation from the warm liquids which many people find emotionally soothing.”
While de Latour notes that by the time warm water reaches your stomach your body has largely regulated its temperature, she says drinking tea or warm water is worth a try. “You’re still hydrating your body at the end of the day.”
Coffee has been proven to stimulate the muscle contractions in your colon that help you poop, but it doesn’t matter whether it’s hot or iced.
Some mineral and sparkling waters contain naturally occurring magnesium sulfate or sodium sulfate, which can have a mild laxative effect, Sauceda says. Magnesium sulfate, for example, is used to treat short-term constipation.
Unlike plain water, which softens stool through hydration alone, magnesium works osmotically, drawing water into your intestines, helping to loosen and move stool.
A review of four randomized, double blind, placebo-controlled studies that looked at whether magnesium sulfate treated constipation found that it did: Across the board, participants who had constipation reported “improved stool consistency and number of bowel movements.” Participants drank up to a liter of mineral water daily during the study period.
Carbonation may also play a small role. Research suggests sparkling water can modestly stimulate digestive activity, though the effect is mild.
Mineral water isn’t a tool de Latour recommends to her patients with constipation, though. “[Magnesium sulfate] can be laxative, but the actual quantity has to be large enough to have that impact,” she says.
The easiest way to tell you’re drinking enough water is to check the color of your urine, de Latour says. Your urine should be clear to pale yellow in color. Dark yellow indicates you may be dehydrated.
Guidelines suggest that the average healthy adult is getting
enough water if they have about 11.5 cups to 15.5 cups of liquid per day. That includes fluid from all sources, including water, but also soda, coffee,
juice, and other drinks.
Individual hydration needs vary widely depending on multiple factors, including:
- Weather; hot weather and high humidity can increase perspiration
- Physical activity, especially long stretches of intense exercise
- Caffeine and alcohol, which are both diuretics
- Medications, which can require increases or decreases in fluid intake
- Underlying medical conditions, such as diabetes, heart disease, liver disease, or kidney disease, which can all change fluid requirements, Burkhart says
- Fiber intake
“If you’re constipated and seeing dark urine, you know for sure you’re not drinking enough water,” de Latour says.
While increasing hydration and fiber can be a solution for constipation, it isn’t a cure-all.
Drinking more water won’t resolve constipation if it stems from:
- Pelvic floor dysfunction
- Motility issues like slow transit constipation
- Side effects from medication
- Lack of exercise
- Changes in your lifestyle, such as travel, pregnancy, or aging
- A problem with how your bowels work, such as irritable bowel syndrome
- Underlying medical conditions, such as thyroid disease, Parkinson’s disease, or celiac disease
- Intestinal blockages
If changes in hydration, fiber, and lifestyle do not help within two to four weeks, it’s time to see your healthcare provider, Burkhart says.
You should also get checked out if you have signs of a more serious condition such as:
- Rectal bleeding or blood in stool
- Unintentional weight loss
- Significant changes in the shape of your stool or stool patterns
- Constipation with serious pain
- A family history of colon cancer
