Kefir, explained

Kefir is a fermented milk drink with a range of supposed health benefits. Which are PR and which are true?
15 June 2020

Interview with 

Paul Cotter, APC Microbiome Ireland


A kefir-containing strawberry smoothie.


Kefir is a fermented milk drink that, over the past few years, has started to appear in UK supermarkets. But in reality it's an ancient beverage, full of live bacteria that have a range of health claims attached. Which of these are true and which are hot air? Phil Sansom heard from Paul Cotter of APC Microbiome Ireland...

Paul - Kefir is a fermented milk and it's made by virtue of adding a kefir grain into normal milk. It carries out the fermentation process; some of the good bugs that are in the grain enter into the milk and start living there and growing and producing things; and then the following morning, you remove your kefir grain from your milk, you use a sieve or some other sort of approach; and you place the grain into fresh milk and begin the process all over again.

Phil - Okay. What actually is kefir?

Paul - It's a consortium, or a group, or a gathering of lots of different microbes; thousands of different microbes all together in a cluster. And it has an appearance, it's quite like a small cauliflower, and it has kind of a slightly slimy texture. The bacteria... certain bacteria within the mix produce a polysaccharide called keferin - kind of a complex sugar - to keep all of the different bacteria and yeast together in a clump.

Phil - And is this, you said it was a grain, is it something that comes from a plant?

Paul - No, so the term grain is a misnomer, so it's not a... it doesn't accurately reflect where it comes from. It originally was developed primarily in Eastern Europe; there's some evidence of some kefir being produced in the Middle East as well. The thinking was that farmers stored some milk in pouches, and those pouches would have come from calf stomachs or goat stomachs, but by virtue of the different microbes that were present in those calf stomachs and the different nutrients that are in the milk, they formed spontaneously there. And then over time, individual kefir grains were passed through families because what happens is every time you ferment a milk, the grain gets a little bit larger, eventually to the point where it kind of breaks in two. And within families or among particular communities, people would keep one grain themselves and then pass the others onto their friends or their siblings or their kids. And that would pass on through the generations over and over.

Phil - Where does it come from today? Are there people making new ones?

Paul - For the most part, people are using grains that they've inherited or gotten from other people. We've studied kefir from lots of different locations around the world and we've gotten them through Ebay or Facebook requests. So the sharing of them has become even easier now. But because they've become so popular, there are slightly different versions of kefir grains that are available right throughout the world. And in a way Western society's just rediscovering them, but they've been there in the background the whole time. And in fact, there's a suggestion that maybe the insufficient consumption of fermented foods for quite some time now has perhaps contributed to some of the problems associated with the gut in Western society and increased levels of allergy and so on and so forth.

Phil- If so, what gap do they fill? What do the kefir grains do when you put them into milk?

Paul - I suppose from a big picture perspective, in Western society, the argument was that we weren't exposed or consuming enough healthy microbes, and just not having enough microbes in our lives in general. So as a consequence of higher levels of hygiene and overuse of antibiotics and whatnot, then our body is just not so used to dealing with microorganisms. And when it comes across harmful microorganisms, sometimes our immune system overreacts. And that's why you have lots of increases in things like inflammatory bowel diseases and allergies and so on and so forth. Coming back to the kefir in particular: what happens there is the various different microbes in the grain enter into the milk, and a subset of them really like the milk and they grow well there. So they can remove lactose, which means that lactose intolerant people can consume it. And then also by interacting or being in close proximity with the gut, they can also produce compounds and trigger different reactions. So they will be sensed by the immune system. And in some cases dampen down the immune system, where you have a case where somebody is susceptible to having a high level of inflammation. Some of the other molecules that they produce can be neurotransmitters - compounds that we normally associate with being in our brain and sending signals there, and telling us whether we should feel good or bad; but we also have lots of neurotransmitters in our gut. And so we can impact on their levels of, we think at least, that we're impacting on our levels of anxiety and stress and so on by virtue of consuming these as well. And then there's lots of other evidence to suggest that the microbes can remove cholesterol, remove cholesterol from food products. There's a multitude of other different things that fermented food microbes can do.

Phil - Good Lord. It sounds like a real cocktail of different effects. How can I be sure this isn't, whatever 'Big Wellness', just trying to promote a new product and it's really just fancy yoghurt?

Paul - Yes. That is a concern of mine in that I agree that Western society has almost gone the other extreme now, and that is overselling fermented foods. And we are one of those who are trying to insist on the requirement that good, standard science and human tests and trials are carried out in order to definitively stand over what an individual fermented foods can do.


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