Fermented milk with a far broader range of live cultures than yoghurt.
Kefir is milk fermented with kefir grains — a symbiotic culture of bacteria
and yeasts. It ferments longer and at cooler temperatures than yoghurt, and the result is
thinner, tangier, slightly fizzy, and considerably more diverse in its microbial content.
That diversity is the point. Yoghurt typically contains two or three bacterial strains. Kefir
routinely contains dozens, plus beneficial yeasts. For anyone interested in fermented food
for gut reasons, kefir is the more interesting option of the two.
The fermentation
also consumes most of the lactose, which is why many people who cannot drink milk find kefir
comfortable.
Per 100g of whole-milk kefir. Exact composition depends on fermentation time and milk used.
Based on the nutrients and fibre this food supplies. These are supporting foods, not treatments.
Start with a small glass. Going straight to a full cup of kefir when
your gut is not used to fermented food will produce a memorable afternoon. Begin with 50ml
and build up over a couple of weeks.
Do not heat it. Cooking kills
the cultures, which is the entire reason you are drinking it. Use it cold — in
smoothies, over muesli, or as a base for a raita-style dip.
The tang increases
with time. Kefir left longer in the fridge keeps fermenting and gets sharper. This
is normal, not spoilage.
Check the label for live cultures. Some
supermarket versions are pasteurised after fermentation, which kills the point.
Fermented dairy consistently outperforms plain milk in research on blood pressure, blood sugar and gut symptoms — more than the nutrient content alone explains. The working explanation is that the live cultures and the compounds they produce during fermentation are doing something the nutrition label does not capture. Kefir's unusually wide range of strains makes it the most-studied version of this effect in ordinary food.
Immunocompromised: live cultures carry a small risk. Ask your
doctor before adding fermented foods.
Milk protein allergy: avoid
— fermentation removes lactose, not casein.
Histamine
intolerance: fermented foods are high in histamine and commonly trigger symptoms.
Trace alcohol: kefir fermentation produces a very small amount of alcohol,
usually under 1%. Worth knowing if you avoid alcohol entirely.
This is information, not a prescription. If you are managing a diagnosed condition or taking medication, talk to your doctor before making a large change to your diet.
Nutrition figures on this page come from standard food composition data. These links let you check the numbers and read the underlying research yourself rather than taking our word for it.