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What is kefir?

Kefir is a cultured, fermented milk drink, originating from the mountainous region that divides Asia and Europe. It’s similar to yogurt but thinner in consistency, making it more suitable for drinking. However, it can also be thickened to form kefir yogurt.

With its tart, sour taste, kefir also has a slight fizz, due to carbon dioxide, a by-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 gut-supporting probiotic bacteria.

Discover our full range of health benefit guides. You can also learn how to make kefir at home or try it in our delicious kefir breakfast smoothie.

Nutritional profile of kefir

One serving (250ml) of whole milk kefir contains approximately:

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  • 145 kcal
  • 8.3g protein
  • 7.5g fat
  • 11g carbs
  • 333mg calcium
  • 28mg magnesium
  • 383mg potassium
  • 0.7mcg B12

Kefir breakfast smoothie in two glasses

Top 10 health benefits of kefir

1. It’s nutrient dense

Dairy foods, including kefir, are good sources of bioavailable protein, fat and carbohydrate. They also contribute valuable vitamins A, D and K; B vitamins; and minerals including calcium.

2. A source of beneficial bacteria and bioactives

Kefir benefits from a wide and diverse composition of beneficial bacteria and yeast, more so than yogurt. These microbes are responsible for producing bioactive compounds that have numerous benefits for our health, from improving digestion to lowering cholesterol levels.

3. May protect against bacterial infection

Some of the bacteria found in kefir are believed to protect against infections. They do this by inhibiting the growth of harmful strains of salmonella, helicobacter pylori and escherichia coli (e. coli).

4. May reduce blood pressure

Animal studies indicate that regular consumption of kefir may be helpful for those with high blood pressure. This is thought to be due to a number of mechanisms, including an inhibitory effect on the angiotensin-converting enzyme (ACE) and the subsequent relaxation of veins and arteries.

5. May reduce the risk of heart disease

Kefir may have other benefits for heart health, including helping to manage blood triglycerides and cholesterol levels. However, more research is needed to confirm this and to clarify the mechanisms involved.

6. May improve digestion

Some people find that regular consumption of kefir supports their digestion, potentially due to its diverse microbial content. These beneficial bacteria may help restore balance in the gut and improve the health and function of the digestive tract.

7. May be suitable for those with lactose intolerance

The lactic acid bacteria (LAB) in kefir are largely responsible for the breaking down of lactose, the natural milk sugar, so there’s some evidence to suggest kefir may be tolerated by those with lactose intolerance. However, you should refer to your GP if you think this may be relevant to you.

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 they can make symptoms worse in some cases.

8. May promote bone health

Traditional kefir made from full-fat cow’s milk is a good source of calcium and vitamin K2, nutrients that are important for bone health.

As we get older, our bones become less dense, which can increase the risk of osteoporosis and fractures, especially in post-menopausal women. Kefir, along with other dairy products, may help support bone health and density.

9. May reduce inflammation

Chronic inflammation is intrinsic to numerous disease conditions, including irritable bowel disease and rheumatoid arthritis. The anti-inflammatory effects of probiotics have been widely reported in studies, although this is an emerging area of research.

While recent studies suggest that LAB bacteria are anti-inflammatory, the question as to whether that translates to a direct benefit from consuming kefir is still unknown.

10. May have a modulatory effect on the immune system

Consuming kefir has been shown to enhance intestinal immunity in animal studies, and may alleviate the inflammatory response associated with allergies and asthma. Further work, including clinical trials, is still needed to better understand the effects of regular human kefir consumption.

Glass with kefir

Are there any side effects?

As the process used to make kefir can vary, it’s difficult to monitor its potency; some products may be richer sources of probiotic bacteria than others. For those who aren’t used to probiotics or fermented foods, it’s sensible to start with a small amount and increase slowly; some people new to kefir report digestive symptoms, such as bloating, constipation or diarrhoea.

Anyone with a compromised immune system or a histamine intolerance should speak to a health professional before introducing or significantly increasing their intake of fermented foods.

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. The fermentation produces beneficial bacteria while reducing the sugar content of the drink.

However, the grains used are different. Water kefir is made with specific grains that rely on water, which don’t work in the same way if put into 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 it doesn’t contain the protein and calcium content found in milk.

How is kefir made?

Traditional milk kefir uses kefir grains and whole cow’s milk, although it can be made from goat’s milk, sheep’s milk and coconut milk, as well as from rice and soya milk alternatives.

Kefir grains are not actually grains at all – they’re small gelatinous beads that look like grains and contain a variety of bacteria and yeasts. Depending on the variety you use, kefir grains may contain 30 or more strains of beneficial bacteria and yeasts. Some of the major strains include lactobacillales – or lactic acid bacteria (LAB).

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 milk sugar) into lactic acid, activating the bacteria to proliferate and grow.

After around 24 hours at room temperature, the grains are strained from the kefir, which is now ready to drink.

The grains are transferred to a fresh batch of milk where they start to reproduce – this cycle can be carried on indefinitely. The grains will multiply as long as they’re kept in fresh milk at the right temperature (ideally about 22-25C). Storing in the fridge with its cool temperature inhibits the fermentation process.

Is it safe to make kefir at home?

Absolutely! However, it’s important to follow recipe instructions closely. Incorrect temperatures, fermentation times or unsterile equipment can cause the kefir grains to spoil and make the kefir unsafe to eat. If you’re curious to try it, check out our guide to making homemade kefir.

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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.

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