Sauerkraut can help with constipation, thanks to a combination of live bacteria, fiber, and fermentation byproducts that work together to keep your gut moving. A 2025 meta-analysis of 19 randomized controlled trials found that fermented food consumption increased bowel movement frequency by an average of 0.6 additional movements per week, improved stool consistency, and reduced intestinal transit time by nearly 14 hours. Sauerkraut isn’t a guaranteed fix, but the science behind it is solid enough to make it worth trying.
Why Sauerkraut Helps Your Gut Move
Sauerkraut works on constipation through multiple pathways at once, which is what makes it more interesting than a simple fiber supplement. Researchers describe it as a “synbiotic whole food,” meaning it delivers probiotics (live beneficial bacteria), prebiotics (fiber that feeds those bacteria), and postbiotics (useful compounds the bacteria have already produced during fermentation) all in a single serving.
The fermentation process populates sauerkraut with several strains of lactic acid bacteria that survive stomach acid and bile salts, allowing them to reach your intestines alive. Once there, they contribute to the community of microbes that regulate how quickly food moves through your digestive tract. These bacteria also produce short-chain fatty acids during fermentation, which stimulate the muscles lining your intestines and draw water into the colon, softening stool and making it easier to pass.
Then there’s the fiber. A 100-gram serving of sauerkraut contains about 2.9 grams of dietary fiber, split roughly 38% soluble and 62% insoluble. The insoluble fiber adds bulk to stool, while the soluble fiber feeds beneficial gut bacteria and helps regulate water content in the intestines. That ratio is actually well-suited for constipation relief, since the insoluble portion keeps things moving physically while the soluble portion supports the microbial activity that drives motility.
What the Research Shows
The strongest evidence comes from a large systematic review and meta-analysis published in Frontiers in Nutrition in 2025, which pooled data from 25 studies and over 4,300 participants. Across 19 randomized controlled trials, fermented food consumption produced statistically significant improvements in bowel movement frequency, stool consistency (measured on the Bristol Stool Form Scale), gastrointestinal symptoms, and intestinal transit time. The analysis also found reductions in bloating, abdominal discomfort, and the overall degree of constipation.
That said, the researchers were honest about limitations. The variability between studies was high, and the European Food Safety Authority’s evaluation framework would rate the overall evidence as “neither convincing nor sufficient” for an official health claim. In practical terms, this means fermented foods like sauerkraut are likely helpful for many people, but the effect size varies and they aren’t a replacement for medical treatment of chronic constipation.
Raw vs. Pasteurized: It Matters
Not all sauerkraut on store shelves will help your digestion equally. The shelf-stable jars sitting in the condiment aisle have almost always been pasteurized, which means heated to a temperature that kills the live bacteria responsible for many of the gut benefits. According to Stanford Medicine, pasteurized fermented foods still contain useful fermentation-derived metabolites but no longer have active microbes.
For constipation relief, you want unpasteurized (raw) sauerkraut, which is typically sold refrigerated. Look for labels that say “raw,” “unpasteurized,” or “naturally fermented.” Some brands add spore-forming bacteria after pasteurization so they can print “contains live cultures” on the label, but these microbes weren’t part of the original fermentation and don’t offer the same benefits. If the sauerkraut is sitting on an unrefrigerated shelf and has a long expiration date, it’s almost certainly been heat-treated.
How Much to Eat
There’s no established clinical dose for sauerkraut and constipation, but most nutrition guidance suggests starting with a small amount and building up. A half-cup serving is a reasonable daily portion. That gives you about 2 grams of fiber, a meaningful dose of live bacteria, and keeps sodium intake from a single serving manageable at around 219 milligrams.
If you’re not used to fermented foods, jumping straight to large portions can temporarily make things worse before they get better. The influx of new bacteria and fermentable fiber can cause gas and bloating in the first few days. Starting with a tablespoon or two and increasing over a week or so gives your gut microbiome time to adjust. Eating sauerkraut alongside a meal rather than on an empty stomach also helps reduce initial discomfort.
Sodium and Other Trade-Offs
The main downside of sauerkraut is its salt content. Fermentation requires salt, and even a modest serving contributes meaningfully to your daily sodium intake. The British Heart Foundation has flagged sauerkraut as a food that, while rich in beneficial probiotics, may be a concern for people managing blood pressure. Checking labels helps, since sodium levels vary significantly between brands. Some artisanal producers use less salt than mass-market versions.
Sauerkraut is also relatively high in histamine, a compound produced during fermentation. Most people handle this fine, but if you tend to get headaches, flushing, or digestive upset from aged cheeses, wine, or other fermented foods, sauerkraut may trigger similar reactions. This isn’t common, but it’s worth noting if you’ve had trouble with fermented foods before.
Getting the Most Benefit
Sauerkraut works best as one piece of a broader approach to constipation rather than a standalone solution. Fiber from other sources (fruits, vegetables, whole grains), adequate water intake, and regular physical activity all support the same gut motility pathways that sauerkraut targets. Adding sauerkraut on top of an otherwise low-fiber, sedentary lifestyle will help, but not as much as combining it with those basics.
Don’t cook your sauerkraut if you want the probiotic benefits. Heat kills the live bacteria just like pasteurization does. Add it as a topping after cooking, mix it into salads, or eat it straight from the jar. If you’re using it in a cooked dish like soup, you’ll still get the fiber and some fermentation byproducts, but you’ll lose the live microbes that are doing much of the heavy lifting for your gut.