Regarded as the king of dairy, the champagne of milk and the ancient food miracle, kefir is the fermented drink taking the world by storm.

Following on from the growth in popularity of superfoods and fermented products (think kombucha, sauerkraut and kimchi), kefir has been dubbed this year's food trend by supermarket giant Woolworths.

"Five or six years ago, we won best new product, which was ironic because kefir is actually really old," says Sharon Flynn, from The Fermentary, a Victorian-based company that, as the name suggests, specialises in fermented products.

"But I'm glad we've had this revival – it only takes two generations for things to be wiped out."

Kefir's history is shrouded in folklore and fervour. The name of the Russian drink believed to date back at least 1000 years comes from the Turkish word keyif (which loosely translates to good feeling) and is said to improve a sense of wellbeing.

What is kefir?

Kefir is a cultured, fermented milk drink that contains beneficial yeast, probiotic bacteria and an abundance of vitamins and minerals. Its proponents boast of its health benefits, particularly for the gut.

It tastes similar to the Turkish yoghurt drink ayran, but with a much more tart taste and a slight fizz – and a barnyard smell.

Kefir's story originates in the Caucasus Mountains, where the folk developed the fermented drink by accident and consumed it in large quantities. Legend has it, those people lived long, healthy lives with little disease.

How is kefir made?

There are two types of kefir: milk and water.

Milk kefir is made with milk from a cow, sheep or goat milk and kefir "grains", which aren't grains at all but a "scoby ", a symbiotic culture of bacteria and yeast, containing about 30 distinct microbes. If looked after properly, milk-kefir scoby is immortal and will double every seven to 10 days. You can pick up the grains from other people making kefir or buy it online.

Commercial kefir starters are available but they are only able to culture milk for a few generations before they die.

Water kefir has a much milder flavour than its milky sibling. It is also made using a scoby, but the bacteria and yeasts feed on carbohydrates instead of lactose. Water kefir can be produced from many liquids, including sugar water, coconut water and soy milk, and is flavoured with fruits, herbs and ginger.

Traditionally, grains were kept in a goat-stomach bag filled with milk and hung by the door. As people came and went, they would knock the bag, helping fermentation along by dispersing the grains. These days, they're kept in jars.

The gelatinous scoby look like clumps of coral. They ferment the milk (or water), and once the fermentation process has been completed, they are removed with a strainer.

Sharon Flynn started making milk kefir commercially about eight years ago using unpasteurised milk, which she says is the traditional way. But since Victoria introduced tough raw milk laws in 2015, Ms Flynn has focused her efforts on making water kefir.

A firm believer in fermented products, the Daylesford-based mum is on a mission to teach people about fermentation and gut health.

"Fermented foods usually carry digestive enzymes that make whatever you're eating more easily digestible," she says. "You don't need to take probiotic capsules if you're eating fermented foods."

Why is kefir good for you?

Unless you've been living under a rock, you've probably heard of gut health, gut bacteria and probiotics.

Kefir is packed with probiotics, yeast and bacteria good for your gut health, according to food scientist Senaka Ranadheera.

"These microorganisms form colonies in our large intestines and colon area and fight against pathogens and they boost our immune system as well."

Dr Ranadheera recommends having probiotic-packed foods, such as yoghurt, kefir and kombucha, at least twice a week to improve your gut health.

Ms Flynn says she was introduced to the world of kefir when her daughter had severe gut problems. A kefir a day, and her daughter's gut pain has completely gone away.

Where can you find kefir?

Once upon a time, in Russian homes, obscure grocery stores and health food stores. But it has now made its way into our major supermarkets.

Woolworths has been stocking kefir, and its Swedish counterpart filmjolk, since July 2017. Its senior nutritionist Natalie Chong says year-on-year sales have almost doubled.

"We know many of our customers are increasingly focusing on gut health and digestive wellness," Ms Chong says.

"As this health trend has grown, we've responded with the introduction of fermented foods with probiotics."

A Coles spokesman says has been an increased demand for health products, including kefir, quark and hemp-based foods.

"The health foods market is continually growing. Not only are we seeing more of our customers buying health foods, but also continuing to purchase these items more frequently."

But you can also make kefir at home. All you need are kefir grains (scoby), milk and patience. And with its booming popularity, grains (both live and dried) are becoming easier to find.