Not all water fights constipation the same way, and the difference comes down to what’s dissolved inside it.
Quick Take
- Randomized trials show magnesium- and sulfate-rich mineral water improves bowel movements more than plain or tap water.
- One major trial found constipation relief in 37.5 percent of people on a higher mineral water dose, compared to 21.1 percent on placebo, by week two.
- A meta-analysis covering 755 people with chronic constipation found high-mineral water worked better than low-mineral water.
- New dietetic guidelines now recommend mineral water as a treatment option, but say drinking more water in general does not help.
The Trial That Changed the Conversation
Researchers ran a randomized, double-blind, placebo-controlled trial on outpatients with functional constipation, testing a magnesium sulfate-rich mineral water sold as Hépar. At week one, nothing much happened. But by week two, results split clearly. Constipation eased in 21.1 percent of the placebo group, 30.9 percent on a half-liter dose, and 37.5 percent on a full liter dose.
The higher-dose group also had fewer hard or lumpy stools by the end of the study, and needed less rescue medication to get relief. A separate analysis of the same trial data found the magnesium water group hit a treatment response rate of 50 percent by day 14, compared to just 29 percent in the control group. That’s not a small gap. That’s a real, measurable difference in how fast people got their gut moving again.
Why Minerals, Not Just Water, Matter
Magnesium and sulfate work on the gut differently than plain water does. They pull water into the colon and speed up movement through the intestines, an effect called an osmotic laxative action. Plain tap water doesn’t carry those minerals in meaningful amounts, so it doesn’t trigger the same pull. That’s the core reason researchers keep finding a gap between mineral water and standard water in these trials.
This isn’t a one-study fluke. A systematic review pooling four separate randomized trials with 755 total participants found 46 percent of people responded to high-mineral water, compared to 32 percent on low-mineral water, a statistically solid difference. Not every trial agreed on how big the effect was or how long it lasted, and one German study found the benefit faded after six weeks of daily use. But the overall direction across studies points the same way.
What Guidelines Now Recommend
A review of over-the-counter constipation therapies found that while some trials missed their exact statistical target on the main measure, secondary results, like stool consistency and bowel frequency at other time points, showed real improvement with magnesium-based treatments. That nuance matters. Constipation trials often measure success in strict, narrow ways, and a treatment can still meaningfully help people even when it misses a rigid technical bar.
Can the minerals in your water affect constipation?
A randomized trial published today found that sulfate- and magnesium-rich mineral water improved bowel frequency at week 2 vs. low-mineral water — but not at week 3.
Interesting. Hydration may be only part of the story.
— Ako | 10,000 Poops Later (@GutTalkAko) September 24, 2026
Dietary guidelines are catching up to the data. Groups now recommend drinking half a liter to a liter and a half of high-mineral water daily for two to six weeks as a legitimate symptomatic treatment for chronic constipation. The same guidance is careful to note that simply drinking more water in general, beyond normal health recommendations, doesn’t move the needle. The mineral content is doing the work, not the volume. For anyone stuck on the toilet wondering if another glass of water will help, the honest answer is: check the label first.
Sources:
frontiersin.org, onlinelibrary.wiley.com, pmc.ncbi.nlm.nih.gov, sciencedirect.com
