Kefir (pronounce as kәFEER) is a fermented drink that is most commonly made from cow milk. Although not as well-known as yogurt, it is becoming increasingly popular as a probiotics drink. Here I have summarized its intriguing history, unique characteristics and recent research on its health benefits.
Although many of us heard about kefir only very recently, kefir has a long and influential history. It is believed to originate in Caucasus mountains at least 2000 years ago. Shepherds used to make them in goatskin sacs. Kefir can only be made from “grains” as will be further described below, which were passed from generation to generation within families and communities.
Kefir, like yogurt, is rich in probiotics. Probiotics are micro-organisms, such as bacteria and yeasts, that are beneficial to health of host. Kefir looks and tastes like liquid yogurt drinks. However, kefir is unique in several ways:
1. According to the latest research using modern technology in genomics and biochemistry, kefir contains about 50~300 different species of micro-organisms 1,2. In comparison, yogurt and probiotic pills usually contains less than 10 species.
2. Micro-organisms in kefir have high survival rate in acid and bile salt in our digestive system3.
3. Kefir has to be made from its specific “starter” – kefir grains. Traditionally kefir grains were passed from generation to generation in families. Nowadays we can easily purchase kefir grains from local and online stores.
4. What are kefir grains? They are called “grains” because they resemble the look of white rice or barley, but they are not actually grains as those grown from crops. Instead, they are clusters of bacteria and yeasts. Yeasts produce polysaccharide filaments called kefiran filaments, which hold together bacteria and yeast and help form the clusters that look like grains.
5. The large number of probiotic species are foundation and source of a very stable commensal and symbiotic system. Therefore, it is easy to culture kefir at home with simple appliances and keep it active for many years.
Studies have shown that kefir can benefit healthy individuals and patients of various conditions, including gastrointestinal diseases, allergies, diabetes, obesity and cancers 1. Several major mechanisms underly the health benefits of probiotics:
1) suppression of pathogenic bacteria in our gut 4;
2) stabilization of intestinal barrier and prevention of pathogens from entering our body 5;
3) reduction of inflammation in intestines 6;
4) restoration of immunity 7;
5) reduction of visceral pain in irritable bowel syndrome and other conditions 8,9;
6). digestion of lactose through lactase generated by probiotics 10.
In the near future, case-control clinical trials are needed in order to establish therapeutic effects of kefir and other probiotic supplements on specific diseases.
Kefir, with its stable culture of large number of probiotic species, is easy to make at home with simple appliances and at low cost. There are several probiotic pills that can be purchased over the counter. However, they all vary in species and numbers of beneficial micro-organisms, and none has been FDA approved. Therefore, kefir has its own advantages as a natural probiotic diet supplement.
Finally, kefir is not for everyone. People who are have congenital and acquired immunodeficiency should consult their physicians before ingesting any probiotics.
1. Rosa DD, Dias MMS, Grześkowiak ŁM, Reis SA, Conceição LL, Peluzio M do CG. Milk kefir : nutritional, microbiological and health benefits. Nutrition Research Reviews 2017;30(1):82–96.
2. Gao X, Li B. Chemical and microbiological characteristics of kefir grains and their fermented dairy products: A review. Cogent Food & Agriculture 2016;2(1):1272152.
3. Talib N, Mohamad NE, Yeap SK, et al. Isolation and Characterization of Lactobacillus spp. from Kefir Samples in Malaysia. Molecules 2019;24(14).
4. Jones SE, Versalovic J. Probiotic Lactobacillus reuteri biofilms produce antimicrobial and anti-inflammatory factors. BMC Microbiol 2009;9:35.
5. Seth A, Yan F, Polk DB, Rao RK. Probiotics ameliorate the hydrogen peroxide-induced epithelial barrier disruption by a PKC- and MAP kinase-dependent mechanism. Am J Physiol Gastrointest Liver Physiol 2008;294(4):G1060-1069.
6. Yan F, Cao H, Cover TL, et al. Colon-specific delivery of a probiotic-derived soluble protein ameliorates intestinal inflammation in mice through an EGFR-dependent mechanism. J Clin Invest 2011;121(6):2242–53.
7. McCarthy J, O’Mahony L, O’Callaghan L, et al. Double blind, placebo controlled trial of two probiotic strains in interleukin 10 knockout mice and mechanistic link with cytokine balance. Gut 2003;52(7):975–80.
8. Pusceddu MM, Gareau MG. Visceral pain: gut microbiota, a new hope? J Biomed Sci 2018;25(1):73.
9. Rousseaux C, Thuru X, Gelot A, et al. Lactobacillus acidophilus modulates intestinal pain and induces opioid and cannabinoid receptors. Nat Med 2007;13(1):35–7.
10. Pakdaman MN, Udani JK, Molina JP, Shahani M. The effects of the DDS-1 strain of lactobacillus on symptomatic relief for lactose intolerance – a randomized, double-blind, placebo-controlled, crossover clinical trial. Nutr J 2016;15(1):56.
I received my MD from PUMC in Beijing China and my Ph.D. in Biochemistry from Stony Brook University on Long Island. Over the years, I have worked in the fields of genetic research and clinical medicine in different parts of the US, including PA, MO, CT, FL, NY and MI. My research has been published in multiple scientific journals. Currently I live in Ann Arbor, MI with my husband and our children and Mango the orange tabby. I love hiking, running, baking, cooking and biking.