Kefir is largely unfamiliar to those of us living in the West, and can initially sound a bit unappealing to our diets and lifestyles that emphasise sterility and clamping down on bacteria. It really isn’t: it has been drunk for millennia, often as a first weaning food given to babies, and tastes rather like a yoghurt drink.

The main benefit of drinking kefir is its impressively high probiotic count. Greater than live yoghurt, greater than sugar and chemical-laden probiotic drinks, this fermented milk drink (it tastes better than that sounds) is a simple, delicious way of helping to keep your gut healthy. This in turn supports all sorts of essential processes, in particular our immune system.

The fermentation process breaks the lactose down, so if you are intolerant to milk you may find you get on just fine with kefir. This gives you back the chance to access all the vitamins and minerals that milk is so rich in, particularly calcium. However, if you are properly allergic to lactose or casein, you can also use the grains to ferment other liquids like coconut milk, soya milk (be aware you can probably eat/drink too much soy), almond milk (unsweetened, or it’s simple to make your own) etc.

The earliest record of fermenting (beer, natch) is around 6,600BC, yet the average Western diet is now extremely low, and often completely deficient in, fermented foods. Around the world fermented foods have always had a valuable place on the daily plate, and in many places continue to do so: think of unpasteurised cheeses, sourdough bread, miso, fermented pickles like sauerkraut and kimchi, wine and beer.

Many of these sources have been pushed out of our modern diet: we’ve swapped sourdough for sliced white; Scotland’s artisan cheese industry is fighting for its life; wine and beer are pasteurised as is most cheese. Yoghurt is often the only food many of us eat that contains live cultures, and then usually alongside a hulking great dose of sugar. Fermented foods contain billions of ‘good bacteria’, as the adverts say (don’t buy the yoghurts you see on TV!), that support the health of our guts and thus the health of everything from our immune system to – studies indicate – our mental wellbeing.

So, bearing in mind kefir is still not stocked in most supermarkets, and can be expensive when it is, how is it made?

Kefir is made from ‘grains’. These look a bit like cauliflower, and are a community of live yeast/bacterial microorganisms. Because they’re alive, they multiply: over the course of several weeks, a tablespoon of grains becomes two. You only need one tablespoon for a pint of milk, so a number of kefir grain-sharing communities have sprung up online, and you can link into these to ask someone to send you their excess grains to get you started. You can also buy them online.

Drain the milk off the grains, but don’t wash them or worry about getting all the milk off. Use about one tablespoon of grains to a pint or a pint and a half of whole milk (it makes sense to use organic, since this is a health drink). Pour into a glass container and leave the lid loose to allow the carbon dioxide produced during fermentation to escape. Keep the jar somewhere that stays at a stable temperature, not by a radiator or in direct sunlight.

In about 12-48 hours (depending on room temp) you’ll see it start to thicken, separate and coagulate. Once this happens it’s ready – I wait until it shows separation towards the middle or bottom of the jar as that indicates it has thickened up. It should smell sour, but not rancid. It tastes sour and slightly carbonated, but not like off milk – basically if it’s drinkable then it’s fine. See below for ways to make it delicious.

If you leave it a bit too long, the whey will separate out at the bottom. Don’t worry, just give it a good stir to re-combine. However, the longer you leave it the stronger and more sour it tastes, so you’ll probably need to whizz it up with a banana to balance it out and/or one of the flavourings below.

Strain the grains out: most information says that metal can kill the grains but apparently this isn’t actually true. I stick to a plastic sieve and a wooden spoon just in case. Keep the grains, put them back in the glass jar and top it up with more milk for the next batch. You don’t need to wash the jar every time – not washing it between a batch or two seems to speed the process up.

Many people drink their kefir just as it is, but personally I find it too sour to enjoy plain. I blend it with a banana and then it’s delicious; even more so if you use frozen banana. I usually also add cinnamon before blending, sometimes unsweetened cocoa powder or peanut butter, or oats/muesli and nuts to turn it into a breakfast. Its tasty enough for my toddler to regard as pudding – like a banana smoothie.

The grains are quite robust, the only real thing that will kill them is washing them in water. They can be frozen, squashed, split etc just fine.

Kefir’s also quite hard to get wrong. I threw my first two batches away because I didn’t have the confidence to drink them, but I now know they would have been fine, I had just never made or drunk something like that before. If your kefir thickens, it’s fermented. Don’t leave it too long each time; if you don’t want to drink it at that point just put the jar in the fridge and the fermentation will slow to a crawl – the kefir and grains will last for weeks in there.