Kefir: what it is, its benefits, types (milk/fruit) and how to use it

Kefir, what is it ? It is a fermented drink obtained using "grains" (a collection of bacteria and yeasts) that transform milk or sweetened water into a tangy, slightly sparkling drink rich in live microorganisms.

• helps to diversify the microbiota (probiotics)
• may improve digestive comfort in some people
• provides nutrients (depending on the base: milk or water)
• a simple alternative to sodas and sugary desserts
• easy to prepare at home, low cost

In practical terms: kefir is not "liquid yogurt." It's a more complex fermentation process involving bacteria and yeasts. The result: a tangy taste, sometimes a slight effervescence, and a composition that depends heavily on the recipe and fermentation time.

The two main types of kefir (and their differences)

We often talk about "kefir" without specifying which type. However, there are two main types, which have different uses.

What are kefir "grains" made of?

Kefir grains are not cereals. They are gelatinous clumps composed of a matrix (polysaccharides + proteins) in which various lactic acid bacteria, acetic acid bacteria, and yeasts live. Their composition varies depending on the origin of the grains, the environment, and how they are maintained.

This point is important: the effects of kefir are not identical from one preparation to another, because the microbial diversity and the duration of fermentation change.

The possible benefits of kefir (what science says, without exaggeration)

Kefir is primarily studied for its impact on the gut microbiota, low-grade inflammation, and certain metabolic parameters. The evidence varies depending on the study (laboratory, animal, human) and the type of kefir.

1) Microbiota and digestion

Kefir provides live microorganisms and fermentation metabolites. In some people, this can lead to improved digestive comfort (bloating, bowel movements). Data on probiotics in general show that the effect depends on the strain and the individual. For a comprehensive overview of probiotics, see a Harvard review for the general public: scientific source.

2) Lactose tolerance (especially milk kefir)

Fermentation consumes some of the lactose. In practice, some lactose-sensitive people tolerate kefir better than milk. This isn't guaranteed: try it in small quantities.

3) Immunity: indirect support

A diverse gut microbiota contributes to healthy immune function. Kefir isn't a magic "booster," but it can contribute, through diet, to a more favorable environment. The WHO emphasizes the importance of diet and lifestyle for overall health: scientific source.

4) Cardiometabolic markers (data still heterogeneous)

Some studies explore the effect of kefir on blood lipids, blood sugar, or blood pressure, but the results are not consistent enough to suggest a significant effect. The key takeaway: kefir can replace a sugary, processed drink, and that in itself is a tangible benefit.

5) Nutritional intake (based on the baseline)

• Milk kefir : protein, calcium, B vitamins (varies depending on the milk).
• Fruit kefir : primarily hydration + organic acids + trace minerals (and variable residual sugar).

How to drink kefir (quantity, timing, frequency)

In practice, start small, then adjust.

• Beginner : 50 to 100 ml/day for 3 to 4 days.
• Next : 150 to 250 ml/day if well tolerated.
• Timing : whenever you want. If you are sensitive, try it during the day rather than before sleeping (slight stimulation/digestion in some).

What this changes: you give your intestine time to adapt (gas/accelerated transit possible at the beginning).

Making your own kefir at home: a simple method (fruit and milk)

Fruit kefir (basic method)

• 1 L of water
• 30 to 50 g of sugar (it mainly serves to feed the fermentation)
• 30 to 60 g of fruit kefir grains
• 1 slice of lemon + 1 dried fig (optional but classic)

Steps : dissolve the sugar, add grains + lemon/fig, cover with a cloth, let ferment for 24 to 48 hours at room temperature, filter, then possible second fermentation in the bottle for 12 to 24 hours for more effervescence (caution: pressure).

Milk kefir (basic method)

• 500 ml to 1 L of milk
• 1 to 2 tablespoons of milk kefir grains

Steps : Put the grains and milk in a jar, cover (without sealing tightly), ferment for 18 to 24 hours, then filter. The longer it ferments, the more acidic and thick it will be.

Common mistakes (and how to avoid them)

• Fermentation too long : very acidic taste, possible digestive discomfort. Adjust to 24 hours and then test.
• Keep everything tightly sealed (especially fruit kefir): risk of overpressure. Use a suitable bottle and open carefully.
• Rinsing the grains with hot water weakens them. Opt for cold water (for fruit) or no rinsing at all (for milk), depending on your routine.
• Dirty utensils : increase the risk of bad taste/contamination. Simple and regular hygiene.
• Drinking too fast or too strongly : start with a small dose.

For whom is kefir useful (and for whom caution is advised)

Useful if…

• are you looking for a simple fermented drink to diversify your diet
• You want to replace sodas/juices with a more "vibrant" option
• You have slightly irregular bowel movements (to be tested gradually)

Caution / medical advice if…

• Immunosuppression (immunosuppressant treatments, transplant, etc.): unpasteurized fermented products should be discussed with your doctor
• Histamine intolerance : fermentation can trigger symptoms in some
• IBS/FODMAP : the effervescence and some residual sugars may be bothersome (try a small dose, longer fermentation is sometimes better tolerated)
• Pregnancy : caution with unpasteurized homemade starter cultures (theoretical microbial risk). If in doubt, opt for well-controlled commercial versions.
• Alcohol : Fruit kefir may contain very small traces of alcohol (variable). If you need to avoid alcohol, take care.

For a cautious and factual view on probiotics and safety, you can consult the NCCIH: scientific source.

Store-bought kefir vs. homemade kefir: which to choose?

• Homemade : economical, customizable, but variable (residual sugar, microbes, gas).
• Commercial : more consistent, sometimes pasteurized (therefore fewer live cultures), beware of added sugars.

In practical terms: if your goal is "living," look for refrigerated, unpasteurized kefir with few ingredients, and start with small quantities.

Conservation and security (simple points)

• In the fridge : slows down fermentation, but the taste still evolves.
• Odor : tangy = normal; rotten/moldy odor = throw away.
• Visual inspection : no mold (fluffy spots). If in doubt, do not consume.
• Bottles : for sparkling wine, use bottles designed for pressure and open regularly.

FAQ: What is kefir? 

Is kefir a probiotic?

Kefir often contains live microorganisms. It can be classified among fermented foods with probiotic potential, but the effect depends on the strains and the preparation.

Kefir and kombucha: what's the difference?

Kombucha ferments sweetened tea using a SCOBY (Symbiotic Culture Of Bacteria and Yeast). Kefir ferments milk or sweetened water using grains. Taste, microorganisms, and uses differ.

Does kefir contain alcohol?

Fruit kefir may contain traces of alcohol (which vary depending on fermentation, sugar, and temperature). The amount is often low, but not guaranteed to be 0%.

Does kefir help with weight loss?

It doesn't make you lose weight "on its own." However, replacing sugary drinks with kefir can help reduce overall calorie intake.

Is it safe to drink kefir every day?

Yes, if you tolerate it. Most people are around 150–250 ml/day, after an adaptation period.

Why do I get bloated with kefir?

Often: too high a dose too quickly, too fizzy a drink, or personal sensitivity (IBS, histamine). Reduce the dose, extend the fermentation time, or stop if symptoms appear.

The grains are multiplying: what to do?

That's normal. Give some away, freeze it (depending on the type), or reduce the amount of grain to maintain a consistent taste.

Can you make kefir without sugar (fruit kefir)?

No, you need a starting sugar to feed the fermentation. Some of it is consumed, but some sugar may remain depending on the time.

Practical tips: choosing your "best" kefir

• For digestion purposes : start small, favour a fermentation that is not too short, observe for 7 to 10 days.
• The goal is a pleasurable drink : fruit kefir + a short second fermentation for a sparkling result, but open carefully.
• Nutritional objective : milk kefir (if tolerated), plain, without added sugar.

To learn more about overall balance (stress, sleep, digestion): see our pages on digestion, immunity, stress and anxiety , and sleep.

Additional scientific reference (reviews and general points on kefir/probiotics): you can explore PubMed via a query "kefir randomized trial" to read the original articles: scientific source.

Conclusion

If you had to remember one thing: kefir is a simple fermented drink to incorporate, interesting for varying fermented foods, provided you go gradually and choose the type (milk or fruit) adapted to your tolerance and your objective.