Kefir and The Gut Microbiome

December 09, 2023 8 min read

Kefir and The Gut Microbiome

Everything needs to eat, or at the very least, consume something that will produce energy. As humans there are many different parts to our diet, be it flavours, textures, and products that are both good and not so good for us.

Our gut microbiota also needs feeding, but what foods does our internal magical bacterial ecosystem like? Watch the ads on TV, or parade the aisles of supermarkets, and there is an array of products bounded before us, being offered up as consumables, that our internal micro bacterial world would love, or really like to get their enzymes into.

One product on the shelf you may have seen is Kefir, a type of fermented food, and that’s exactly what we shall be looking at in this article.

What is Kefir?

Kefir is a fermented food made by adding Kefir grain to liquids and has been around for at least 4000 years. It has shown up at different times along the way, one example is in the 19th century when it was said to provide nourishment for people suffering from tuberculosis[i].

Kefir is a probiotic, and contains live cultures such as:

  • Bifidobacterium bifidum
  • Lactobacillus acidophilus
  • Lactobacillus delbrueckii subsp,bulgaricus
  • Streptococcus thermophilus
  • Lactobacillus helveticus
  • Lactobacillus kefiranofaciens
  • Leuconostoc and Lactococcus lactis[ii]

Being probiotic, fermented foods like Kefir fit right in when it comes to our microbiome world. This is due by and large to the fact their content regarding bacterial strains matches those already in our own bacterial arsenal[iii]. They also interact symbiotically with the prebiotic fibres we eat, helping to keep our gut microbiome balanced[iv].

Types of kefir

Kefir grains are small clusters packed with microorganisms. They are a sort of yoghurt starter and are usually white and gelatinous and vary in their size. They are formed or grown from existing grains, not grown from seeds out of the ground. Kefir grains are made by a symbiotic mix of probiotic bacteria strains, including Lactic acid bacteria, acetic acid bacteria, and yeast.

Different types of kefir can be produced using specific grains. The most common kefir is milk kefir, but other types include:

  • nut milk
  • juice
  • water

Is kefir the save as live yoghurt?

No. Although live yoghurt contains probiotic bacteria just like kefir does, kefir is made from grains and has a huge diverse range of beneficial bacteria, some of which are exclusive to this fermented beverage.

What is the role of fermented foods in the diet?

Fermented foods are foods that have undergone fermentation, an anaerobic process where bacteria and yeasts break down certain foods and transform them into something else, like sugar into alcohol. There is a huge array of fermented foods available including kefir. You’ve probably heard of or experimented with others like kimchi, sauerkraut and miso.

Research is mounting and shows a diet containing some fermented foods could bring health benefits. Even if only a small percentage of the fermented foods consumed make it into the gut after the stomach acid bath, they will begin interactions with our existing bacteria and begin the processes that provide us with health-promoting benefits.  

Health benefits of kefir

The health benefits of kefir are implicit in some chronic illnesses. These include effects that are:

  • anti-oxidative
  • anti-inflammatory
  • anti-microbial
  • anti-diabetic
  • anti-hypercholesterolemic
  • anti-hypertensive effects.

Once in the gut and amongst the microbiota, kefir can be altered and used within different substrates, this diversity means it can be instrumental in many bioactivities relating to combating chronic diseases and promoting health[v][vi].

Promotes bacterial balance

Due to the presence of probiotic bacteria in kefir, interaction with the microbiota is easy. According to some studies, each serving has the potential to deliver up to 100 different species of bacteria, and billions of, colony-forming units (CFUs).

This in itself will promote a balanced gut microbiota. Even in those with no chronic illness, a balanced microbiota is important. In fact, if you want to keep chronic illness at bay this balance is essential. That’s because the higher the bacterial diversity, the healthier your gut microbiome will be!


Researchers are continually finding that fermented products could influence blood sugar control. Kefir is also on the list of these products.

Ostadrahimi, et al., (2015) conducted a study involving 60 type II diabetic patients split into 2 groups. One group of 30 was given 600 ml of kefir daily for 8 weeks. The results after 8 weeks showed a significant decrease in blood glucose levels.

The study concluded that probiotic milk products like kefir can be useful in the medical nutrition management of diabetes[vii]

Cardiometabolic diseases

A review by Pimenta et al., (2018) investigated if kefir has any beneficial role in chronic cardiometabolic diseases including, vascular endothelial dysfunction, hypertension, dyslipidemia, and insulin resistance[viii].

The study used a selection of reports that had displayed results showing the beneficial role kefir may play in improving cardiometabolic disease. The main findings were that kefir could:

  • Bolster endothelial cell recruitment, these are important for new blood vessel formation[ix]
  • Reduce reactive species. This is reducing oxidants and free radicals that can slow and even halt the progression of diseases[x].
  • Reinforce the balance of the gut microbiota. A balanced gut microbiota is a more favourable environment for positive chemical reactions to take place enhancing our health potential[xi].
  • Improve production of anti-inflammatory cytokines. The reactions of these immunoregulatory molecules play a major role in the regulation of the immune response, the human shield against disease[xii].
  • Stop angiotensin-converting enzyme. This process halts the production of angiotensin 2, a chemical reaction that leads to the narrowing of the blood vessels. This could lead to high blood pressure[xiii].
  • Improve the balance vagal/sympathetic nervous system. This is a system that oversees many vital body functions, it is also instrumental in the gut-brain-axis, a communication system that is essential to our existence[xiv]

The study concluded that in some processes, kefir appeared to improve the outcome, but more research is needed in order to ascertain better details of the role kefir plays.

Kefir and anti-cancer properties

Sharifi et al.,(2017) also state that kefir has potential health benefits, including anti-inflammatory, antibacterial, anti-fungal, and anti-allergic effects. They also show that many studies have found that kefir can act on different cancers, including colorectal.

It also suggested that the bioactive compounds kefir possesses like antioxidants,  polysaccharides and peptides could hold back genomic instability, meaning it can help stop damage occurring to DNA, which in turn can slow or halt the development of cancers and tumours[xv][xvi].

Can kefir be bad for you?

Kefir does contain probiotics, so if you are just starting to introduce these into your diet, you may want to do this gradually, to prevent side effects like gas and bloating. But for most people, fermented foods are safe to eat.

However, if you are keen to try kefir and are lactose intolerant, you should check the label of products like milk kefir first. Remember there are many dairy-free alternatives available, too like water kefir or even coconut kefir.

Human milk oligosaccharides (HMOs) and kefir

From what has been published about kefir, it’s a pretty cool complementary product for the gut microbiome with promising health potential, even if more research is needed to fine tune the findings.

Once the probiotics are delivered by kefir and other fermented foods and supplements and have seeded your gut, it’s time to keep them well-fed. One way to do that is with another cool product. This time it’s a prebiotic and it’s HMOs.

HMOs are glycans that we initially get from human milk and interact with the gut microbiota, an interaction that sees them play an integral part in reactions that lead to the production of essential fermentation end products like acetate, butyrate, and propionate.

These short-chain fatty acids in conjunction with the gut bacteria protect against pathogens, communicate with the central nervous system, regulate metabolism, influence the processes of the brain, regulate hormone production, contribute to drug metabolism, and regulate the immune function.

HMOs also feed and protect the probiotics from invading pathogens, as well as help teach our defence system how to defend. Quite an impressive list, a predetermined chemical armoury. Imagine the potential health benefits on the horizon by consuming daily doses of Kefir and HMOs. 


Having been around for thousands of years, kefir clearly has provenance, and that’s being reinforced with today’s science and current technology. From balancing the gut microbiota to interactions that fortunately have a detrimental effect on pathogens taking hold of our future is a win-win for humankind.

Add to this, human milk oligosaccharides and our internal armoury have an even better chance of providing the essential protection we need from invading pathogens and chronic illness.

Written byLeanne Edermaniger, M.Sc. Leanne is a professional science writer who specializes in human health and enjoys writing about all things related to the gut microbiome. 


[i] Azizi NF, Kumar MR, Yeap SK, Abdullah JO, Khalid M, Omar AR, Osman MA, Mortadza SAS, Alitheen NB. Kefir and Its Biological Activities. Foods. 2021 May 27;10(6):1210. doi: 10.3390/foods10061210. PMID: 34071977; PMCID: PMC8226494.

[ii] Bourrie BC, Willing BP, Cotter PD. The microbiota and health promoting characteristics of the fermented beverage kefir. Frontiers in Microbiology. 2016;7. 

[iii] Tóth AG, Csabai I, Maróti G, Jerzsele Á, Dubecz A, Patai ÁV, Judge MF, Nagy SÁ, Makrai L, Bányai K, Szita G, Solymosi N. A glimpse of antimicrobial resistance gene diversity in kefir and yoghurt. Sci Rep. 2020 Dec 31;10(1):22458. doi: 10.1038/s41598-020-80444-5. PMID: 33384459; PMCID: PMC7775456.

[iv] Prado MR, Blandón LM, Vandenberghe LP, Rodrigues C, Castro GR, Thomaz-Soccol V, Soccol CR. Milk kefir: composition, microbial cultures, biological activities, and related products. Front Microbiol. 2015 Oct 30;6:1177. doi: 10.3389/fmicb.2015.01177. PMID: 26579086; PMCID: PMC4626640.

[v] Peluzio MDCG, Dias MME, Martinez JA, Milagro FI. Kefir and Intestinal Microbiota Modulation: Implications in Human Health. Front Nutr. 2021 Feb 22;8:638740. doi: 10.3389/fnut.2021.638740. PMID: 33693024; PMCID: PMC7938729.

[vi] Azizi NF, Kumar MR, Yeap SK, Abdullah JO, Khalid M, Omar AR, Osman MA, Mortadza SAS, Alitheen NB. Kefir and Its Biological Activities. Foods. 2021 May 27;10(6):1210. doi: 10.3390/foods10061210. PMID: 34071977; PMCID: PMC8226494.

[vii] Ostadrahimi A, Taghizadeh A, Mobasseri M, Farrin N, Payahoo L, Beyramalipoor Gheshlaghi Z, Vahedjabbari M. Effect of probiotic fermented milk (kefir) on glycemic control and lipid profile in type 2 diabetic patients: a randomized double-blind placebo-controlled clinical trial. Iran J Public Health. 2015 Feb;44(2):228-37. PMID: 25905057; PMCID: PMC4401881.

[viii] Pimenta FS, Luaces-Regueira M, Ton AM, Campagnaro BP, Campos-Toimil M, Pereira TM, Vasquez EC. Mechanisms of Action of Kefir in Chronic Cardiovascular and Metabolic Diseases. Cell Physiol Biochem. 2018;48(5):1901-1914. doi: 10.1159/000492511. Epub 2018 Aug 9. PMID: 30092577.

[ix]Medina RJ, Barber CL, Sabatier F, Dignat-George F, Melero-Martin JM, Khosrotehrani K, Ohneda O, Randi AM, Chan JKY, Yamaguchi T, Van Hinsbergh VWM, Yoder MC, Stitt AW. Endothelial Progenitors: A Consensus Statement on Nomenclature. Stem Cells Transl Med. 2017 May;6(5):1316-1320. doi: 10.1002/sctm.16-0360. Epub 2017 Mar 10. PMID: 28296182; PMCID: PMC5442722.

[x] Ray PD, Huang BW, Tsuji Y. Reactive oxygen species (ROS) homeostasis and redox regulation in cellular signaling. Cell Signal. 2012 May;24(5):981-90. doi: 10.1016/j.cellsig.2012.01.008. Epub 2012 Jan 20. PMID: 22286106; PMCID: PMC3454471.

[xi] Jandhyala SM, Talukdar R, Subramanyam C, Vuyyuru H, Sasikala M, Nageshwar Reddy D. Role of the normal gut microbiota. World J Gastroenterol. 2015 Aug 7;21(29):8787-803. doi: 10.3748/wjg.v21.i29.8787. PMID: 26269668; PMCID: PMC4528021.

[xii] Opal SM, DePalo VA. Anti-inflammatory cytokines. Chest. 2000 Apr;117(4):1162-72. doi: 10.1378/chest.117.4.1162. PMID: 10767254.

[xiii] Herman LL, Padala SA, Ahmed I, et al. Angiotensin-Converting Enzyme Inhibitors (ACEI) [Updated 2023 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:

[xiv] Breit S, Kupferberg A, Rogler G, Hasler G. Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Front Psychiatry. 2018 Mar 13;9:44. doi: 10.3389/fpsyt.2018.00044. PMID: 29593576; PMCID: PMC5859128.

[xv] Sharifi M, Moridnia A, Mortazavi D, Salehi M, Bagheri M, Sheikhi A. Kefir: a powerful probiotics with anticancer properties. Med Oncol. 2017 Sep 27;34(11):183. doi: 10.1007/s12032-017-1044-9. PMID: 28956261.

[xvi] Moreno-Celis U, García-Gasca T, Mejía C. Apoptosis-Induced Compensatory Proliferation in Cancer. In: Sergi CM, editor. Metastasis [Internet]. Brisbane (AU): Exon Publications; 2022 May 3. Chapter 11. Available from: doi: 10.36255/exon-publications.metastasis.apoptosis-proliferation


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