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[James Talbot]

Karachaysand Balkars are the creators of kefir and kefir yeast.[4][5] The drink originated in the North Caucasus, in particular the Elbrus region along the upper mountainous sections of Karachay and Balkaria, from where it came to Russia,[6][7] and from there it spread worldwide. Kefir is a common breakfast, lunch or dinner drink consumed in countries of western Eurasia. Kefir is consumed at any time of the day, such as with zelnik (zeljanica), burek and banitsa/gibanica, as well as in cold soups.

Traditional kefir was made in goatskin bags that were hung near a doorway; the bags would be knocked by anyone passing through to keep the milk and kefir grains well mixed.[11] In Karachay-Balkar, gıpı has a connection with gıpıt (wineskin). It was under the name wineskin that Karachay kefir was distributed in the second half of the 19th century and at the beginning of the 20th century.[12][13] Kefir spread from the former Soviet Union to the rest of Europe, Canada, Japan, and the United States by the early 21st century.[9][14][15] It has become known in parts of Latin America as blgaros, or "Bulgarians".

Traditional kefir is fermented at ambient temperatures, generally overnight. Fermentation of the lactose yields a sour, carbonated, slightly alcoholic beverage, with a consistency and taste similar to drinkable yogurt.[16]

The kefir grains initiating the fermentation are initially created by auto-aggregations of Lactobacillus kefiranofaciens and Kazachstania turicensis, where multiple biofilm producers cause the surfaces to adhere which form a three dimensional microcolony.[17][18][19] The biofilm is a matrix of heteropolysaccharides called kefiran, which is composed of equal proportions of glucose and galactose.[9] It resembles small cauliflower grains, with color ranging from white to creamy yellow. A complex and highly variable symbiotic community can be found in these grains, which can include acetic acid bacteria (such as Acetobacter aceti and A. rasens), yeasts (such as Candida kefyr and Saccharomyces cerevisiae) and a number of Lactobacillus species, such as L. parakefiri, L. kefiranofaciens (and subsp. kefirgranum[20]), L. kefiri,[21] etc.[9] While some microbes predominate, Lactobacillus species are always present.[22] The microbe flora can vary between batches of kefir due to factors such as the kefir grains rising out of the milk while fermenting or curds forming around the grains, as well as temperature.[23] Additionally, Tibetan kefir composition differs from that of the Russian kefir, Irish kefir, Taiwan kefir and Turkey fermented beverage with kefir.[9] In recent years, the use of freeze-dried starter culture has become common due to stability of the fermentation result, because the species of microbes are selected in laboratory conditions, as well as easy transportation.[24][25][26]

During fermentation, changes in the composition of ingredients occur. Lactose, the sugar present in milk, is broken down mostly to lactic acid (25%) by the lactic acid bacteria, which results in acidification.[22] Propionibacteria further break down some of the lactic acid into propionic acid (these bacteria also carry out the same fermentation in Swiss cheese). Other substances that contribute to the flavor of kefir are pyruvic acid, acetic acid, diacetyl and acetoin (both of which contribute a "buttery" flavor), citric acid, acetaldehyde, and amino acids resulting from protein breakdown.[27]

Several dietary minerals are found in kefir, such as calcium, iron, phosphorus, magnesium, potassium, sodium, copper, molybdenum, manganese, and zinc in amounts that have not been standardized to a reputable nutrient database.[39][37] Kefir contains vitamins in variable amounts, including vitamin A, vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B3 (niacin), vitamin B6 (pyridoxine), vitamin B9 (folic acid), vitamin B12 (cyanocobalamin), vitamin C, vitamin D, and vitamin E.[39] Essential amino acids found in kefir include methionine, cysteine, tryptophan, phenylalanine, tyrosine, leucine, isoleucine, threonine, lysine, and valine.[39][37]

Probiotic bacteria found in kefir products include: Lactobacillus acidophilus, Bifidobacterium bifidum, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus, Lactobacillus kefiranofaciens, Lactococcus lactis, and Leuconostoc species.[22][36][40] Lactobacilli in kefir may exist in concentrations varying from approximately 1 million to 1 billion colony-forming units per milliliter, and are the bacteria responsible for the synthesis of the polysaccharide kefiran.[3]

The resulting fermented liquid may be drunk, used in recipes, or kept aside in a sealed container for additional time to undergo a secondary fermentation. Because of its acidity the beverage should not be stored in reactive metal containers such as aluminium, copper, or zinc, as these may leach into it over time. The shelf life, unrefrigerated, is up to thirty days.[41]

Kefir can be made using freeze-dried cultures commonly available in powder form from health food stores. A portion of the resulting kefir can be saved to be used a number of times to propagate further fermentations but ultimately does not form grains.

In Taiwan, researchers were able to produce kefir in a laboratory using microorganisms isolated from kefir grains. They report that the resulting kefir drink had chemical properties similar to homemade kefir.[43]

Kefir grains will ferment the milk from most mammals and will continue to grow in such milk. Typical animal milks used include cow, goat, and sheep, each with varying organoleptic (flavor, aroma, and texture) and nutritional qualities. Raw milk has been traditionally used.

Milk sugar is not essential for the synthesis of the polysaccharide that makes up the grains (kefiran), and rice hydrolysate is a suitable alternative medium.[44] Additionally, kefir grains will reproduce when fermenting soy milk, although they will change in appearance and size due to the differing proteins available to them.[45]

As it contains Lactobacillus bacteria, kefir can be used to make a sourdough starter.[46] It is also useful as a buttermilk substitute in baking. Kefir is one of the main ingredients in cold borscht soup in Lithuania, also known in Poland as Lithuanian cold soup (chłodnik litewski), and other countries. The kefir-based soup okroshka is common across the former Soviet Union. Kefir may be used in place of milk on cereal, granola, milkshakes, salad dressing, ice cream, smoothies and soup.

Louisa writes about nutrition and health for news and science outlets. She has a passion for plant-based diets and a functional approach to health. In her spare time, Louisa enjoys the outdoors and gardening. She is also a qualified florist. Louisa loves cooking healthy food and encouraging people to try plant-based!

Based in the vibrant seaside city of Brighton, U.K., Lana Burgess is passionate about writing empowering healthcare content. She is a communications manager for EIT Health, part of the European Institute of Innovation and Technology. Outspoken about mental health, Lana has a diagnosis of bipolar disorder and believes that sharing experiences reduces stigma. She manages her mental health through yoga, journaling, dancing, running, sea swimming, and taking medication.

Catharine began writing news for Medical News Today in 2006. Before that, she had various roles in independent consultancy and in the computer industry. She has a Ph.D. from Manchester Business School for research on job stress in small and large organizations. What Catharine most enjoys about writing is putting across the salient points about the latest health and medical research for busy, informed readers. When she is not news writing, Catharine enjoys spending time on her narrowboat, walking, listening to audio books, and being with friends and family. Her current challenge is increasing the biodiversity of her vegetable garden.

Kefir is a type of fermented dairy product. People make it by adding bacteria and yeast cultures to milk. The cultures feed on natural sugars in the milk. This allows them to multiply, creating a fermented drink.

Kefir has a tart and tangy flavor and a consistency similar to drinkable yogurt. Due to the fermentation process, kefir may taste slightly carbonated. This happens because the microbes produce gases as they digest the sugars in the milk.

A small 2015 study in Iran compared the effects of consuming kefir and conventionally fermented milk on blood sugar levels in people living with diabetes. Participants who consumed kefir had significantly lower fasting blood sugar levels than those who consumed conventionally fermented milk.

A 2020 review suggests that kefir could have a range of benefits for people with diabetes and obesity. It may modulate diabetes-related markers. However, larger-scale research is necessary to support this.

A 2017 study looked at changes in cholesterol levels among females with obesity or overweight who drank low-fat dairy products or kefir. The participants drank either two servings a day of low-fat dairy products, four servings a day of low-fat dairy products, or four servings a day of kefir.

After eight weeks, those who drank kefir showed significant decreases in their total cholesterol levels, and in their low-density lipoprotein cholesterol levels, compared to those who drank only two servings per day of low-fat dairy products. Participants who consumed four servings per day of low-fat dairy products also had lower cholesterol levels.

More recently, a 2023 study compared the effects of two types of kefir on the health of people with high LDL cholesterol. One type had traditional kefir organisms, while the other did not. Participants drank both kinds of kefir for four weeks each, with a break in between.

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