The health benefits of kefir

What is kefir, how is it made, and is it healthy? Jo Lewin explores the benefits of kefir and why it may be a good source of probiotics and calcium.

Kefir in a jar

Kefir is a cultured, fermented milk drink, originally from the mountainous region that divides Asia and Europe. It is similar to yogurt – but thinner in consistency, making it more of a drink. Kefir has a tart, sour taste and a slight ‘fizz’, due to carbon dioxide – the end product of the fermentation process. The length of the fermentation time determines the flavour. Kefir is a good source of calcium and is rich in probiotic bacteria.

How is it made?

The method of making kefir is one of the main differences between kefir and yogurt. Traditional milk kefir uses kefir grains and whole cow’s milk – although now you can find it made from goat’s milk, sheep’s milk and coconut milk as well as from rice and soy milk alternatives. Kefir grains are not actually grains at all – they are small gelatinous beads that look like grains and contain a variety of bacteria and yeasts. The grains are placed in a glass jar or bowl, soaked in milk, covered and left at room temperature for a minimum of 24 hours. This enables the bacteria and yeast to ferment the lactose (natural sugar in milk) into lactic acid, activating the bacteria to proliferate and grow.

After around 24 hours at room temperature, the grains are strained from the kefir and transferred to a fresh batch of milk and used again to enable them to keep reproducing – this cycle can be carried on indefinitely. The strained kefir is now ready to drink.

The grains will multiply as long as they are kept in fresh milk at the right temperature (ideally about 22-25C). When the product is put in the fridge, the cool temperature inhibits the fermentation process.

Is it safe to make kefir at home?

As kefir is a fermented product, strict guidelines must be adhered to in order to ensure that it is safe for consumption – if made incorrectly it has the potential to make you ill. Therefore, if you are fermenting at home, make sure you follow the recipe instructions closely. Incorrect temperatures, fermentation times, or unsterile equipment can cause the food to spoil, making it unsafe to eat.

Nutritional benefits

Milk is a good source of protein and calcium, and kefir is no different. However, it has the added benefits of probiotics. Probiotics are known as ‘friendly bacteria’ that may ease IBS symptoms such as bloating and digestive distress in some people. 

Enjoying kefir regularly has also been associated with benefits for blood pressure, cholesterol balance and blood sugar management. Plus, depending on the variety that you use, kefir grains may contain 30 or more strains of beneficial bacteria and yeasts. Some of the major strains include the lactobacillales – or lactic acid bacteria (LAB).

Kefir milk

Does kefir improve digestion?

Some people find that kefir improves their digestion, potentially due to its probiotic content. Probiotics may help restore balance in the gut, thereby improving digestion.

The fermentation process also helps to break down the lactose in milk, so there is some evidence to suggest that kefir may be tolerated by those who suffer from lactose intolerance. However, you should speak to your GP if you think you may be lactose intolerant.

Those with a diagnosed condition such as inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS) should consult with a GP or dietitian before introducing fermented foods because, in some cases, they can make symptoms worse.

Does kefir help you to lose weight?

Obesity has been linked to an imbalance in gut bacteria. However, which strain of bacteria has an effect is less clear. Some evidence suggests that the lactobacillus species, or LAB group, like those found in kefir are associated with changes in weight, but more robust evidence is needed before recommendations can be made.

However, other evidence contradicts these findings, suggesting instead that probiotics do not decrease body weight or affect weight loss/BMI. Clearly this is an area for further research. 

Does kefir promote better bone health?

Traditional kefir made from cow's milk is a good source of calcium and vitamin K, nutrients which are both important for bone health. As we get older, our bones become weaker, which can increase the risk of osteoporosis and fractures, especially in post-menopausal women. Kefir, along with other dairy products, is a useful source of dietary calcium.

Does kefir reduce inflammation?

Inflammation is involved in a number of diseases such as IBD or rheumatoid arthritis. The anti-inflammatory and immunomodulatory effects of probiotics have been reported in some studies, although this is an emerging area of research. It does appear that the LAB bacteria are anti-inflammatory but whether that translates directly to kefir is still unknown.

Are there any side effects?

As the process used to make kefir can vary between brands, it is hard to monitor its potency, so some products may be richer sources of probiotic bacteria than others. For those who are not used to probiotics or fermented foods, it is sensible to start with a small amount and increase slowly. Some people report digestive symptoms such as bloating, constipation or diarrhoea when introducing fermented foods to the diet. Anyone with a compromised immune system or a histamine intolerance should speak to a health professional before introducing or increasing their fermented food intake.

What about water kefir?

Water kefir is made in a similar way to milk kefir. The kefir grains are placed in sugared water and the same fermentation process occurs (as in milk). The fermentation produces beneficial bacteria while reducing the sugar content of the drink. It's important to note that the grains are different –water kefir is made with specific grains that rely on water, and will not work in the same way if put in milk or milk substitutes. Cane sugar or fruit juice can be used to sweeten the water. Water kefir is a great alternative source of probiotic bacteria for those who are following a dairy-free diet but does not contain the same protein and calcium content that's provided by milk.

Kefir was recently featured in BBC’s Trust Me I’m A Doctor.

More healthy guides...

Health benefits of lemon water
Health benefits of green tea
Health benefits of coconut milk
Health benefits of bananas
Health benefits of ginger

This article was reviewed on 1st November 2019 by Kerry Torrens.

Kerry Torrens BSc. (Hons) PgCert MBANT is a Registered Nutritionist with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.

Jo Lewin is a registered nutritionist (RNutr) with the Association for Nutrition with a specialism in public health. Follow her on Twitter @nutri_jo.

All health content on is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.


Comments, questions and tips

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12th Apr, 2019
Absolute nonsense to tell people not to make it at home. Thousands of people make it themselves at home with no issues. Homemade is far superior to shop bought. I also ferment my own sourkraut I suppose that's dangerous as well?
5th Dec, 2018
I was pleased to read all of the earlier comments. It's almost like a writer posted an article on BBC Goodfood recommending that we'd be safer buying ready meals. I was given my original grains three years ago by a neighbour who had herself been nurturing them for years. I have passed surpluses back to her, and to friends. I will add one detail that i have not seen elsewhere - the greater the quantity of grains, the quicker the kefir brews. The original few tablespoonfuls took over 24 hours, but I often end up with enough grains to fill a jamjar. I like my kefir mild, and it's ready in 8 to 10 hours.
3rd Jun, 2018
I can't believe tht BBC GoodFood would allow someone to tell us NOT to make Kefir at home. It is perfectly safe to do so. I started making milk kefir when I first heard about it. I had looked in the shops for it and, when I eventually found a shop that did sell it, the price was so ridiculously high that I could not possibly be able to afford around £2 per day!! Maybe the writer produces kefir and wants us to buy that instead? My kefir tastes wonderful, much better than the shop bought stuff. So, go on everyone, make your own, don't heed this terrible advice.
26th Apr, 2018
Kefir is totally safe to make at home. I bought 2 tablespoons of grains from a company on Amazon for about £7. I have made kefir with these for over a year now. I find that using full cream milk that has been mixed through (usually labelled 'smooth' on the bottle) works best and gives a thick creamy consistency. I went on holiday for 14 days and left my grains in the fridge in a litre of fc milk and the grains did more than survive, they fermented the milk perfectly in the two weeks. I make water kefir too very successfully from grains bought from Amazon for about a fiver. ,
29th Mar, 2018
I actually cannot believe this article says NOT to make it at home and to buy it from a packet haha! It's the quickest and easiest thing to make and totally safe as long as you make sure the jar is washed properly. I'm 28, working mum, 2 young kids and every few nights I chuck a load of the grains into a mason jar, pour in some milk and forget about it for a day or so then it's good to go. If I can do it anyone can !
6th Jan, 2018
I have been making kefir with grains for years now. Not only is it safe to make at home, with normal milk hygiene, but it has more bacteria and yeasts than any commercial kefir I have found, either here or in the USA, therefore much better for you. Kefir along with occasional sauerkraut and kimchi, has kept me IBS free for years now too. As others have said, kefir is quite capable of killing pathogens. There is plenty of research to prove that. Have a go, with common sense and confidence and enjoy the benefits.
Umdi Mensum
2nd Nov, 2017
Where I live we don't buy kefir grains, we get them for free, from friends or strangers. We grow them at home, make creamy kefir, kefir cheese, liquid kefir, we share recipes. More than 24 hours brewing is OK, it depends on how tart or thick you want your kefir.
longdancer's picture
1st Nov, 2017
I found all the forms of lacto-fermentation that I tried (Kefir, Tibicos, Viili, yoghurt) to be very safe and cheap for home production. These live cultures overwhelm any pathogens that might be lurking in your kitchen so just a normal wash of utensils is all you need. I ended up making far too much of the stuff and had to give it away. Its delicious but it made me very sleepy.
31st Oct, 2017
"Mountainous region that divides Asia and Europe"...which is? Are you talking about Ural? Caucasus? Cuz both of these "mountainous regions" fit the bill. Why not just use an actual name of this "mountainous region" instead of pretending to be a short story writer? In like 99% of cases Ural is viewed as the main border between Europe and Asia, so it doesn't even make sense to refer to this while talking about Caucasus. As for kefir, yes, it's super-healthy and offers more benefits than milk or yogurt.Tasty yoo.
4th May, 2017
It's absolutely safe to make kefir at home as long as usual common measures regarding hygiene are taken.


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