What is Kefir?

Kefir tradition is said to have started thousands of years ago. The etimology of kefir was the Turkish word keyif which means "good feeling."   In 1908, Elie Metchnikoff, a Nobel-prize winning biologist at the Pasteur Institute, attributed the long and healthy life of the people of the Caucasus Mountains to their consumption of soured milk, most probably kefir.

Kefir is a fermented milk beverage resulted from the action of bacteria and yeasts that exist in symbiotic association in kefir grains. Because of large number of microorganisms present and their microbial interactions possible bioactive compounds resulting of microbial metabolism, kefir earns the status of a natural probiotic. Due to the benefits associated with the use this beverage, kefir is designated as the 21st century drink.  In fact, an increase in kefir consumption in many countries has currently been reported, mostly due to its unique sensory properties and beneficial effects on human health.

Several studies have shown that kefir has antimicrobial, antitumor, anticarcinogenic and immunomodulatory activity and also improve lactose digestion. Elie Metchnikoff, a Nobel-prize winning biologist at the Pasteur Institute suggested that lactobacilli might counteract the putrefactive effects of gastrointestinal metabolism.

Generally, kefir grains contain a relatively stable and specific microbiota enclosed in a matrix of polysaccharides and proteins. Microbial interactions in kefir are complex due to the composition of kefir grains, which seems to differ among different studies, although some predominant Lactobacillus species are always present.

Kefir is characterized by its yeast-specific, distinct flavor and an effervescent feeling in the mouth. The main products of kefir fermentation are lactic acid, ethanol and CO2, which confer this beverage viscosity and acidity. Diacetyl, acetaldehyde, ethyl and amino acids, as minor components, contribute to the flavor composition of kefir.

There are two main types of kefir: milk kefir, and water kefir. In milk group we include alternative milk kefir, such as nut, soy, rice or coconut milk, whereas in water group we can include coconut water or fruit juice. Basically, each groups is made with fermentation by its corresponding kefir grains.


Milk kefir grains are a combination of live bacteria and yeasts that exist in a symbiotic matrix on a surface of a complex polysaccharide with a casein core. The make-up of kefir grains can vary depending on the culturing location and culturing conditions, which means the community of lactic acid bacteria and yeasts can be highly variable in batches of kefir cultured in different places by different people.

Bacteria Strains Commonly Found in Milk Kefir Grains:

Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus casei, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. delbrueckii, Lactobacillus delbrueckii subsp. lactis, Lactobacillus helveticus, Lactobacillus kefiranofaciens subsp. kefiranofaciens, Lactobacillus kefiri, Lactobacillus paracasei subsp. paracasei, Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus sake, Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis, Lactococcus lactis, Leuconostoc mesenteroides subsp. cremoris, Leuconostoc mesenteroides subsp. dextranicum, Leuconostoc mesenteroides subsp. mesenteroides, Pseudomonas, Pseudomonas fluorescens, Pseudomonas putida, Streptococcus thermophilus

Yeast Strains Commonly Found in Milk Kefir Grains:

Candida humilis, Kazachstania unispora, Kazachstania exigua, Kluyveromyces siamensis, Kluyveromyces lactis, Kluyveromyces marxianus, Saccharomyces cerevisiae, Saccharomyces martiniae, Saccharomyces unisporus



Water kefir grains are a combination of live bacteria and yeasts that exist in a symbiotic matrix on a surface of a complex polysaccharide. Water kefir grain composition can vary depending on culturing location and conditions, resulting in a highly variable community of lactic acid bacteria and yeasts.

Following is the list of bacteria and yeast strains found in water kefir grains according to one scientific study.* The strains listed may include numerous subspecies and variants. Please note that this list is for general informational purposes only. We do not test individual batches of water kefir grains for yeast and bacteria content; therefore, we cannot make any guarantees as to the exact probiotic composition of our water kefir grains.

Bacteria Strains Commonly Found in Water Kefir Grains

  • Species Lactobacillus: L. brevis, L. casei, L. hilgardii, L. hordei, L. nagelii
  • Species Leuconostoc: L. citreum, L. mesenteroides
  • Species Acetobacter: A. fabarum, A. orientalis
  • Species Streptococcus: S. lactis


Yeast Strains Commonly Found in Water Kefir Grains

Hanseniaospora valbyensis, Lachancea fermentati, Saccharomyces cerevisiae, Zygotorulaspora florentina


Kefir versus Kombucha

Kombucha can be an aid to digestive system. In addition to the beneficial bacteria, it also contains some acids and enzymes to aid in the breaking down of food. Kombucha tea can contain caffeine, however, depending on the tea used.

Water kefir is more of a general probiotic beverage. While it does contain enzymes and acids, they don’t seem to have quite as strong an effect as those in kombucha. However, water kefir contains a greater number of bacteria strains than those found in kombucha.

Milk kefir is said to have more bacteria and yeast strains than water kefir by significant amounts. It also contains protein, but also is derived from dairy or substitute milk products that not everybody is keen on. Many swear by its mighty power to help with digestive issues as  it coats the intestinal linings.

In short, all these probiotic beverages are beneficial in aiding natural systems of the body, and providing excellent hydration. Depending on your needs, consuming one or or the other is a matter of individual taste. Check our Probiotic Mic drink line that combines both kombucha and water kefir in a bottle for maximum live probiotic benefits.


* Source:água.pdf


Read: What is Kombucha? What is Milk Kefir? What is Water Kefir?