Type the words “how to improve your gut health” into Google and it won’t take long until you come across the advice to add fermented foods into your diet. 

It’s no secret that foods such as kimchi, kombucha and miso can help to promote a healthier and more diverse gut microbiome; gut health guru Dr Tim Spector is constantly singing the praises of our fermented friends.

And one of the fermented foods most often recommended for gut health is kefir. While most kefir you’ll find in supermarkets will typically be dairy-based – it’s often compared to a yoghurt drink – there are a growing number of water kefirs on offer for anyone who follows a vegan diet or simply can’t tolerate dairy.

But that raises the question: is it simply the process of consuming a fermented food that matters or are some varieties of fermented foods more potent than others? Is water kefir or milk kefir better for gut health and hydration, or is it just a matter of preference?  

Water kefir is a type of fermented drink made using water kefir grains. These ‘grains’ do not contain any grain or gluten; instead, they’re gelatinous blobs that are made by combining helpful bacteria and yeast.

These grains are then added to sugar water, coconut water or fruit juice, where the bacteria feed on the sugar in the liquid to create the final drink. This process usually takes between 24-48 hours, during which the bacteria produce lactic acid, alcohol and carbon dioxide.

But don’t worry – you’re not going to get drunk from a glass of water kefir. All fermentation processes produce alcohol, but the amount of alcohol in the final product is minimal. It may be slightly higher if you make your own water kefir at home.

The primary difference between water kefir and milk kefir is how it’s made. Milk kefir is not only milk-based – meaning milk is used rather than water to create the final product – but the grains used to make it are also made from milk.

Again, these grains have nothing to do with the plants grown in fields – they’re gelatinous, cloudy lumps of fermented milk that contain bacteria. However, unlike water kefir grains, these ones cannot be artificially made, only grown from pre-existing ones. 

The ones we use today are believed to date back 2,000 years to the people of the North Caucus region (located between present-day Georgia and Russia), who unknowingly produced them by storing milk in bottles made of animal skins. It’s thought that over time the micro-organisms in the raw milk and those in the bottles mixed to form a symbiotic colony of yeast and bacteria – making the kefir grains we still use now.  

Grain and base difference aside, the process of making water kefir and milk kefir is the same – the grains are added to a medium (in this case milk) and left to ferment.

The difference in ingredients between water kefir and dairy kefir means they possess different nutrients, explains Yasmeen Alsumait, a nutritionist and life coach. “Milk kefir is packed with calcium, vitamin B12 and protein from the milk, whereas water kefir’s nutrients depend on what kind of sugar or juice you use,” she says. “Water kefir is also lactose-free.” 

Whether water kefir or milk kefir is better for you will depend on what you’re looking for. In terms of bacteria, however, there’s only really one winner: milk kefir.

“Milk-based kefir usually has a wider range of probiotics because milk is a more complex environment for those bacteria and yeasts,” Alsumait explains. However, that doesn’t mean you should sleep on water kefir. The types of bacteria you’ll find in water kefir and milk kefir do vary, and research suggests that milk kefir has a wider range of good bacteria than water-based kefir. But water-based kefirs are still packed full of good bacteria, making them a great option for anyone looking to boost the health and diversity of their gut microbiome.

And that’s not forgetting the fact that water-based kefir can be made into lots of different flavours by using different juices or waters as the base. 

Perhaps the most surprising area of contention between the two is their hydrating abilities. While you might think water kefir would take home the prize here, studies have shown that milk can be more hydrating than water because of its lactose, protein and fat content, which help to slow the emptying of fluid from the stomach.

With that being said, the fermentation process involved in making milk kefir does remove much of the lactose from the milk, so that reduces its hydrating properties slightly.

Overall, Alsumait says, choosing between water kefir and milk kefir is just a question of suitability. “Both forms of kefir are superstars for gut health – they’re packed with probiotics that are great for your digestive system.

“The best choice really depends on what works for your diet and preferences. If you can’t do dairy, water kefir is an excellent alternative. But if you’re all about getting those extra nutrients from milk, then dairy kefir might be your go-to.” 

Images: Getty