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Packed with live microbes like the ones found in our gut, the ancient fermented drink kefir has become popular with those conscious of maintaining a well-balanced gut microbiota, writes dietitian and nutritionist Lauren Marino.

There’s a bit of a buzz at the moment around kefir, and sooner or later it’s likely that one of your clients will ask you about it. So, what is it, and what does it do?

Kefir is a fermented drink made by adding kefir grains to either milk or a sugary water. The grains look like small pieces of cauliflower and are a complex mix of bacteria and yeast. By adding these to the milk or sugar water, the kefir grain creates a fermentation process with the available sugar, resulting in a drink with a very mild natural fizz. In the case of most kefirs where dairy milk is used, the naturally occurring lactose is the sugar that undergoes the fermentation process. Kefir can also be made with plant-based milks such as coconut or soy, and with coconut water, as long as there is a small amount of available sugar to ferment.

Although it has become increasingly popular over the past couple of years, kefir actually originated thousands of years ago in the Caucasas Mountains in the former Soviet Union. The word ‘kefir’ is said to have originated from the Turkish word ‘keyif’ which means ‘good feeling’ and relates to the feeling of health and wellbeing when it’s consumed.

Kefir and gut health

Kefir has become more prevalent as we learn more about gut health. Due to the fermenting process to create kefir, live microbes like the ones found in our gut microbiota are produced. This may contribute to creating a well-balanced gut microbiota.

A well-balanced gut microbiota

Our gut microbiota is incredibly diverse, with 10 to 100 trillion interrelated bacterial cells calling our intestine home. They perform a range of functions such as increasing our immunity1, preventing the growth of harmful species, and producing hormones, vitamins and amino acids. They can also strengthen the gut barrier, deactivate toxins and influence gut movement and function.2

Imbalance of the gut microbiota is associated with obesity3, is linked to chronic inflammation diseases such as rheumatoid arthritis and irritable bowel disease, and may even be capable of causing disease by allowing infection. So, maintaining a well-balanced and healthy gut microbiota is important to maintain overall wellbeing.

Other benefits of kefir

Kefir has also been shown to be an anti-fungal and anti-bacterial which can protect against infection4. These properties may be part of the reason why a study has shown that short term consumption of kefir can reduce risk of tooth decay5. A small-scale study has shown that daily kefir may reduce the symptoms of chronic constipation, which is not surprising as we know that a healthy gut microbiota is responsible for maintaining bowel movements.6 As both of these studies are small and not of high quality, however, more research and studies are required before these potential benefits influence nutrition recommendations.

Although the kefir grains are called grains, they do not contain any gluten, so kefir is fine for those with coeliac disease and gluten sensitivities. It is also low in lactose because the lactose is the sugar that undergoes fermentation, meaning it may be better tolerated than regular milk or yoghurt by those with lactose intolerance or irritable bowel syndrome.

Nutrients in kefir

Other qualities of a dairy-based kefir are its high calcium content, which encourages strong bones. In fact, a small-scale study showed increased bone mineral density in patients with osteoporosis who supplemented with kefir plus a calcium supplement.7 This new research is exciting but needs to be investigated further.

Kefir is also a good source of protein, which increases meal satisfaction and fullness and assists in muscle building. Kefir also contains Vitamin B12, which can prevent fatigue and help keep the body’s nerve and blood cells healthy.

More high-quality research is required to back up some of the anecdotal and theoretical claims around this fermented drink. However, kefir is a nutritious, safe and inexpensive food that makes a great addition to most people’s diets.

Although more high-quality research is required to back up some of the anecdotal and theoretical claims around this fermented drink, for most people kefir is a nutritious, safe and inexpensive addition to their diet.


  1. Sommer, F. and Bäckhed, F. (2013). The gut microbiota — masters of host development and physiology. Nature Reviews Microbiology, 11(4), pp.227-238.
  2. Rossi, M. and Croman, E. (2019). Eat yourself healthy. Penguin Books Ltd, p.29.
  3. Ley, R. (2010). Obesity and the human microbiome. Current Opinion in Gastroenterology, 26(1), pp.5-11.
  4. Guzel-Seydim ZB, Kok-Tas T, Greene AK, Seydim AC. Review: Functional properties of kefir. Crit Rev Food Sci Nutr 2011; 51: 261-8
  5. Cogulu, D., Topaloglu-Ak, A., Caglar, E., Sandalli, N., Karagozlu, C., Ersin, N. and Yerlikaya, O. (2010). Potential effects of a multistrain probiotic-kefir on salivary Streptococcus mutans and Lactobacillus spp. Journal of Dental Sciences, 5(3), pp.144-149.
  6. Turan, I., Dedeli, O., Bor, S. and Ilter, T. (2015). Effects of a kefir supplement on symptoms, colonic transit, and bowel satisfaction score in patients with chronic constipation: A pilot study. The Turkish Journal of Gastroenterology, 25(6), pp.650-656.
  7. Tu, M., Chen, H., Tung, Y., Kao, C., Hu, F. and Chen, C. (2015). Short-Term Effects of Kefir-Fermented Milk Consumption on Bone Mineral Density and Bone Metabolism in a Randomized Clinical Trial of Osteoporotic Patients. PLOS ONE, 10(12), p.e0144231.

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