Is fermented milk good for constipation? A look at probiotics, science, and relief

November 11, 2025 •

4 min read

According to the National Institutes of Health, constipation is one of the most common gastrointestinal disorders, affecting millions of people worldwide. This has led many to explore natural remedies, with the question 'Is fermented milk good for constipation?' becoming increasingly common in the search for relief.

Quick Summary

Fermented milk, such as kefir and certain yogurts, is beneficial for constipation by introducing probiotics that improve gut microbiota and bowel movements.

Key Points

Probiotics for relief: Fermented milk is a good source of probiotics, which can help improve constipation by regulating gut bacteria.
Increased stool frequency: Studies show that consistent intake of probiotic-enriched fermented milk can increase the frequency of bowel movements.
Improved stool consistency: Fermented milk consumption can lead to softer, more comfortable-to-pass stools by increasing their water content.
Kefir offers greater diversity: Kefir generally contains a wider range of probiotic strains and yeasts compared to most yogurts, which may offer broader gut health benefits.
Strain-specific effects: The effectiveness against constipation can depend on the specific probiotic strain. For example, Bifidobacterium lactis has been shown to be more effective for transit time than some other strains.
Lifestyle matters: Fermented milk works best as part of a holistic approach that includes a high-fiber diet, adequate hydration, and regular exercise.

The Gut Microbiota and Constipation: A Vicious Cycle

Your gastrointestinal tract is home to trillions of microorganisms, collectively known as the gut microbiota. A healthy, balanced microbiota is crucial for proper digestion, nutrient absorption, and immune function. However, an imbalance in these microbial communities, a state called dysbiosis, is strongly associated with gastrointestinal issues, including constipation.

Constipation, characterized by infrequent bowel movements, hard stools, and straining, can disrupt this delicate balance further. A slower colonic transit time can alter the microbial environment, potentially leading to a decrease in beneficial bacteria like Bifidobacterium and Lactobacillus. This creates a self-reinforcing cycle where dysbiosis contributes to constipation, and constipation, in turn, exacerbates the dysbiosis.

How Fermented Milk Provides a Solution

Fermented milk products act as a delivery vehicle for probiotics—live, beneficial bacteria and yeasts that can help restore balance to the gut. The fermentation process creates an environment rich in these microorganisms. When consumed, these probiotics work to regulate the intestinal environment and normalize bowel function through several key mechanisms.

The Mechanisms of Action

Increasing Short-Chain Fatty Acids (SCFAs): Probiotic bacteria ferment dietary fibers in the colon to produce SCFAs like acetate, propionate, and butyrate. These compounds can help lower the intestinal pH, which promotes peristalsis (the muscle contractions that move stool) and discourages the growth of some harmful bacteria. Butyrate, in particular, is a vital energy source for colon cells, promoting a healthy mucosal barrier.
Shortening Colonic Transit Time: Multiple studies have shown that consuming certain probiotics, particularly certain Bifidobacterium lactis strains, can reduce whole-gut transit time. This means that waste moves through the colon more efficiently, which is a direct benefit for constipated individuals.
Improving Stool Characteristics: Probiotics can increase the water content in stool, making it softer and easier to pass. This leads to a significant improvement in stool consistency, often resulting in a more optimal Bristol Stool Chart score.
Modulating Inflammation: Some fermented dairy products can help reduce intestinal inflammation, which can be a contributing factor in some cases of constipation. By regulating inflammatory markers, probiotics can support overall gut health and improve motility.

Not All Fermented Milk Is Created Equal

The effectiveness of fermented milk for constipation depends on the specific probiotic strains and their viability. While many products contain probiotics, not all are equally beneficial for digestive issues.

Yogurt vs. Kefir: A Comparison

To understand which fermented milk might be best for you, consider the differences between popular options like yogurt and kefir.


Feature	Yogurt (Probiotic-Enriched)	Kefir
Probiotic Diversity	Typically contains 2-4 strains (e.g., L. bulgaricus, S. thermophilus, added L. acidophilus or B. lactis).	Contains a much wider variety of bacteria and yeasts (up to 12 or more strains).
Key Strains for Constipation	Strains like Bifidobacterium lactis DN-173 010 and HN019 are well-researched for their efficacy.	Includes Lactobacillus kefiranofaciens, which has shown promise in animal studies for relieving constipation.
Consistency	Varies from firm gel to drinkable, but generally thicker than milk.	A thinner, more drinkable consistency similar to a thick buttermilk.
Mechanism of Action	Strain-specific effects, often studied for increasing defecation frequency and improving stool consistency.	Broader modulation of the gut microbiota, production of kefiran, and positive effects on bowel movements.
Lactose Content	Lower lactose than milk, as bacteria consume it during fermentation, making it tolerable for some with intolerance.	Even lower in lactose than yogurt due to a more extensive fermentation process.

How to Incorporate Fermented Milk for Constipation Relief

For best results, consider these tips when adding fermented milk to your diet:

Choose the Right Product: Look for products that explicitly state they contain "live and active cultures" and specify the probiotic strains. Look for strains like Bifidobacterium lactis or consider kefir for its greater diversity.
Maintain Consistency: Regular, daily consumption is key. Many studies that showed positive effects on constipation involved consistent intake over several weeks.
Start Slowly: If you are not used to fermented foods, start with a small serving size and gradually increase it. A sudden large intake can sometimes cause temporary bloating or gas.
Consider Timing: Some studies suggest that consuming probiotics with a meal can help protect the bacteria as they pass through the stomach.
Stay Hydrated: Water is essential for high-fiber diets and for keeping stools soft. Ensure you are drinking plenty of fluids alongside your fermented milk.
Listen to Your Body: What works for one person may not work for another. Monitor your symptoms and adjust your intake accordingly. If you have conditions like Irritable Bowel Syndrome (IBS), individual responses to fermented milk can vary.

Other Lifestyle Factors That Affect Constipation

Fermented milk should be seen as one component of a broader strategy for managing constipation. For optimal digestive health, consider these additional steps:

Increase Fiber Intake: Incorporate a variety of high-fiber foods like fruits, vegetables, whole grains, and legumes into your diet.
Regular Exercise: Physical activity helps stimulate intestinal motility and can significantly aid in bowel regularity.
Manage Stress: The gut-brain axis means stress can impact digestive function. Stress-reduction techniques may improve constipation symptoms.
Stay Hydrated: As mentioned, drinking plenty of water and caffeine-free fluids is crucial for soft stools.

Conclusion

Fermented milk can be a valuable dietary addition for those experiencing constipation. The probiotics it contains, particularly certain strains of Bifidobacterium and Lactobacillus, can positively influence the gut microbiota, increase stool frequency and water content, and shorten colonic transit time. While results can be strain-dependent, consistent consumption of high-quality products like probiotic-rich yogurt or kefir is a promising and natural approach to improving digestive health and finding relief. Always remember to combine this with other healthy lifestyle choices for the most significant benefit.

This article is for informational purposes only and is not medical advice. Consult with a healthcare professional before starting any new dietary supplements.

Frequently Asked Questions

Kefir is often cited as a powerful option for constipation relief due to its high diversity of probiotic strains. However, probiotic-enriched yogurts containing specific strains like Bifidobacterium lactis have also shown significant benefits in studies.

The timeframe can vary by individual and product. Some studies have shown noticeable improvements in stool frequency and consistency within 2-4 weeks of consistent, daily consumption.

While uncommon, some sensitive individuals might experience temporary digestive upset, such as bloating or gas, when first introducing new probiotics. In rare cases, high amounts of certain dairy components could contribute to constipation in some people, but this is less likely with low-lactose fermented products.

Fermented milk products like yogurt and kefir contain less lactose than regular milk because the bacteria consume much of it during fermentation. Many people with lactose intolerance find these products easier to digest and can tolerate them well.

Heat-treated or pasteurized fermented milk may not contain live and active cultures, which are the source of most probiotic benefits. Look for products that specify "live and active cultures" on the label to ensure you are getting viable probiotics.

Some studies have shown that certain probiotic strains in fermented milk can help increase stool frequency in children with functional constipation. However, it is essential to consult a pediatrician before giving supplements to children and to use appropriate dosages.

There is conflicting evidence on the best time to consume probiotics. Some experts suggest that consuming probiotics with food may help buffer stomach acid and increase bacterial survival. It is more important to consume it consistently than to worry about exact timing.