Here at Poseymom, we sell both water kefir and milk kefir. Both products have the word “kefir” in their name, so there is sometimes some confusion about what the difference is between them.

And, just to get it out there, there are a few major differences.

One interesting question we got recently was if they are interchangeable. In other words, some people have water kefir in their homes and they want to know if they can just put their water kefir grains in milk and transform the grains to milk kefir grains.

Conversely, some customers want to make a transformation in the other direction. They want to take milk kefir, put the grains in water and sugar, transforming the milk kefir into water kefir.

So, can you do that? Are water kefir and milk kefir essentially the same thing? Are they interchangeable?

The short answer: No. They are completely different.

Yes, they both have “kefir” in the name. And yet, they are both probiotic products, just like kombucha tea is a probiotic product. But that doesn’t mean that they are the same thing.

The key difference is in what they eat.

Water kefir grains eat the sugars you add to their water. As they feed on the sugar and minerals, they ferment the water, leaving a healthy probiotic drink for you to enjoy.

Milk kefir grains don’t feed on sugar. Milk, after all, isn’t that sugary. So milk kefir grains feed on the proteins and lactose in the milk.

This is good news for those of you that are lactose intolerant. Milk that has been fermented with milk kefir has a huge reduction in lactose, so most people are able to drink it with no problems.

So there you have it. A simple question answered. Can you transform water kefir into milk kefir (or vise versa)? No. They are different cultures, and they even feed on different things. Water kefir would not be able to thrive in milk because there isn’t enough sugar, and milk kefir can’t survive at all in sugar water because it needs lactose to live and grow.

Until next time, stay healthy and proud!