Milk kefir is one of those fermented beverages that are making a comeback in the ‘health’ kitchen, to the point where it is sometimes presented as a universal solution: light digestion, calmer tummy, smoother transit, better tolerance of lactose, ‘boosted’ microbiota, etc. The result is that many people take the plunge, try it for a few days, then wonder why they don’t feel anything… or why they have more gas at the start. And in the midst of all this noise, one simple question deserves an answer: is milk kefir really good for digestion?
The most honest answer is: it can be, but not in the same way for everyone, and not with ‘miracle’ promises. The digestive effects of kefir depend on what you call ‘digestion’, your sensitivity (lactose, irritable bowel, eating habits), the quantity consumed, the type of kefir, and also the quality of the routine (fermentation too long = very acid kefir, fermentation too short = milder effect, etc.). Above all, the scientific evidence is there, but it varies according to the results studied: some data are fairly solid (particularly on lactose digestion), while others are promising but still heterogeneous (overall digestive symptoms, microbiota, inflammation).
This guide provides a comprehensive and useful answer:
In fact, many people who embrace kefir also like to explore kombucha to diversify tastes and routines. If you want to add another fermentation at home, our SCOBY Kombucha can be a great base to start a regular fermentation: you can find it on the Natural Probio shop via the SCOBY Kombucha page (natural authentic kombucha strain).
When someone says “I have bad digestion”, this can mean a number of things:
Milk kefir may (or may not) act on some of these axes, but not with the same force.
There are three possible mechanisms (to be understood without over-promising):
The “may” is important: with probiotics and fermented products, the effect depends enormously on the strain, the dose, the context and the targeted symptoms.
If your “digestive problem” is mainly linked to lactose, kefir is particularly interesting.
A study of adults with lactose maldigestion assessed whether kefir improves lactose digestion and tolerance: the specific aim was to measure exhaled hydrogen (a marker of colonic fermentation of undigested lactose) and symptoms. The results suggested improved lactose digestion/tolerance with kefir compared with milk. The results suggested better lactose digestion/tolerance with kefir compared with milk(PubMed).
Important: this does not mean that “everyone with an intolerance can drink a litre of kefir without worry”. But it does support the idea that, for some people, milk kefir is better tolerated than milk.
More recent research and reviews of randomised controlled trials are looking at the effect of (fermented) kefir on different markers and symptoms in humans. A systematic review of randomised trials on kefir highlights that the benefits claimed are often studied, but that the overall evidence remains limited and variable depending on the study and the results.(PubMed)
There are also recent studies (2025) showing a reduction in gastrointestinal symptoms in certain contexts, but as is often the case, the details (population, duration, type of kefir, comparator) are very important for correct interpretation.(jn.nutrition.org)
At the same time, broader reviews of fermented dairy products (not just kefir) conclude that the impact on GI symptoms and immune biomarkers may be zero in some studies, with no harmful effects reported in the included studies – a reminder of the reality that there is no “guaranteed effect” for everyone(OUP Academic).
A recent randomised controlled trial showed that consumption of kefir can modify the composition of the microbiota in adults under controlled conditions (standardised meals, shared environment). This suggests a measurable effect, although the next question is “does this modulation translate into a felt benefit (bloating, transit, pain)?” – It’s not always direct.(Frontiers)
With regard to probiotics in general, organisations such as the NCCIH (NIH) point out that there are areas where certain probiotics show benefits (e.g. certain types of diarrhoea), but that there is a lack of strong evidence for many uses and that everything depends on the formulation and the indication.(NCCIH)
In terms of European regulations, “probiotic” health claims are highly regulated, and there have historically been opinions/assessments (e.g. EFSA on lactose digestion for live yoghurt cultures) which show that the benefits must be demonstrated precisely, for a specific claim(European Food Safety Authority).
To put it plainly: yes, kefir is an interesting fermented beverage, but we’re avoiding slogans. We prefer the method: test, observe, adjust.
If your symptoms are mainly milk-related (gas, bloating, diarrhoea) and you suspect lactose, kefir is worth a trial. As mentioned above, fermentation and the presence of cultures can improve tolerance in some people(PubMed).
Compared with certain more acidic fermentations, milk kefir is easy to incorporate: in small portions, at breakfast or as a snack, with a stable routine.
Kefir is not a pill. It works best when it’s part of an overall healthy diet: fibre, hydration, regular meals, and a reduction in ultra-processed excesses. And that’s where a lot of people feel they’re getting better, as a whole, not just from one food.
It’s a very common situation: you start a fermented drink, and for the first few days you have more intestinal activity, sometimes more gas.
There are several possible explanations:
The solution is not to give up immediately, but to reduce the dose and gradually increase it.
A simple approach to testing the digestive effect:
This logic follows what is often recommended with probiotics: the effect depends on tolerance and regularity, and certain effects (or lack of effect) cannot be judged over 48 hours.(NCCIH)
Many prefer :
There is no “magic” hour. The aim is to choose a time when you are consistent.
Kefir that has been fermented for a long time becomes more acidic. If you are sensitive :
Whole milk can make the perception softer. Some people feel the acidity less.
This is the most important thing: start small and build up slowly.
It’s the most popular subject, and the most variable.
Studies on GI symptoms with fermented foods show precisely this variability: sometimes there is a benefit, sometimes there is no measurable benefit, and the effect depends on the populations and protocols.(OUP Academic)
The smartest way to “test for bloating” is :
Kefir generally contains a combination of bacteria and yeast, but the word ‘probiotic’ is a tricky one: in scientific and regulatory terms, ‘probiotic’ implies precise criteria and claims, and not all consumer promises are validated as authorised claims.(Food Safety Authority of Ireland)
In practice, what matters to you is :
And if you like the world of fermentation, you can also vary: many people alternate between kefir and kombucha. Kombucha, with a stable culture, is also controlled by acidity and time. You can start a home fermentation via the SCOBY Kombucha page (authentic natural kombucha strain) on Natural Probio.
I’m deliberately being cautious here, because this is health.
Products containing live micro-organisms can raise questions in people with very weakened immunity, who are undergoing heavy treatment, etc. In these situations, it is best to talk to a health professional, and avoid self-experimentation. In these situations, it is preferable to talk to a health professional, and to avoid self-experimentation.
If you have significant, persistent symptoms, weight loss, blood in the stools, severe pain or a complex diagnosis, kefir should not replace medical advice.
Kefir is still a dairy product: if you’re allergic to milk proteins, it’s not suitable.
Measure whether kefir improves your digestive comfort (bloating, tolerance of dairy products, transit, feeling of heaviness), without making you believe in a miracle solution.
In some people with lactose maldigestion, studies suggest an improvement in digestion/tolerance compared with milk(PubMed).
Yes, this can happen. Reduce the dose and increase it gradually.
For lactose tolerance, some people feel it quickly. For overall digestive comfort, give yourself 1 to 2 weeks of consistent testing. Data on probiotics/ferments show that the effects are variable and context-dependent.(NCCIH)
No. It can help some people with certain discomforts, but it is not a medical treatment.
Recent controlled trials suggest a modulation of the composition of the microbiota after consumption of kefir, at least in the short term.(Frontiers)
Milk kefir can be a good digestive ally for many people, especially when the question revolves around lactose tolerance and greater comfort with fermented dairy products. Human data also show interesting results on certain symptoms and on the microbiota, but the overall picture remains heterogeneous, so the most reliable approach is to test gradually, observe, and adjust (dose, fermentation, type of milk).
And if you like the world of fermented drinks, variety can be an excellent strategy: some days kefir, other days kombucha, depending on your mood and tolerance. To start making your own kombucha with a stable culture, you can find our SCOBY Kombucha (authentic natural kombucha strain) on Natural Probio.
