My Little Jar of Liquid Gold: The Science and Benefits of Kefir

Published: 02 October 2026

I'll be honest, the first time I tasted homemade kefir I pulled a face. Tangy, a bit sour, a tiny fizz on the tongue that I didn't expect from milk. Then I went back for a second sip. And a third. Now there's a jar on my kitchen counter just about every day of the year, with a cloth over the top and those little white grains quietly doing their thing.

So I thought it was time I told you what's actually happening in that jar, because the science behind kefir honestly fascinates me.

First things first: what is kefir?

Kefir is a fermented milk drink. You take milk (cow, goat or sheep) and add kefir grains. And no, they're not grains like wheat or oats. When I first held them I thought they looked like tiny bits of cauliflower, soft and a bit rubbery and slippery between your fingers.

Those little clusters are made of protein and a special sugar called kefiran, and they're home to a whole community of bacteria and yeasts living together. Scientists call it a symbiotic community. I call it my little colony.

Yoghurt is usually made with just two or three types of bacteria, kept warm. Kefir is different. It ferments at room temperature, right there on my counter, with dozens of different microbes all working together.

Who lives in my jar?

This is the part I love. In every batch there are:

• Lactic acid bacteria, which do most of the fermenting. One of them, Lactobacillus kefiranofaciens, is the one that actually builds the grain. There's also Lactobacillus kefiri, Lactobacillus helveticus, and others from the Lactococcus, Leuconostoc and Streptococcus families.
• Acetic acid bacteria like Acetobacter aceti, which give kefir that extra tangy edge.
• Yeasts such as Saccharomyces cerevisiae and Kluyveromyces marxianus. They make the carbon dioxide, and that's where the little fizz comes from.

(Sindi et al., 2020; Prado et al., 2015)

When I open the jar in the morning and get that sour, slightly yeasty smell, I know they've been busy.

What happens to the lactose?

While the kefir ferments, the bacteria eat most of the lactose (the natural sugar in milk) and turn it into lactic acid. That's why it tastes sour and not sweet like fresh milk. Researchers have also found that the live enzymes in kefir can help break down the lactose that's left once you drink it, so lots of people with mild lactose sensitivity find kefir easier to drink than ordinary milk (Prado et al., 2015). The longer I leave my jar, the tangier it gets, and whey water starts to separate at the bottom. I sieve it off for baking, and the kefir that's left is lovely and thick.

Kefir and your gut

This is where it gets exciting. A 2025 study in healthy adults found that drinking kefir regularly was linked to a greater variety of bacteria in the gut, with more Lactobacillus and Lactococcus. It also supported the pathways that produce short-chain fatty acids (Choi, 2025). Those short-chain fatty acids feed the cells lining the colon and help keep the gut wall strong.

Inflammation and immunity

During fermentation, kefir makes bioactive peptides and kefiran, and scientists have studied both for their effect on the immune system. Animal and human studies have found that kefir can lower inflammatory markers such as IL-6 and help fight oxidative stress (Prado et al., 2015). A 2024 study in women with polycystic ovary syndrome also looked at how kefir affects their gut bacteria and health outcomes (Çıtar Dazıroğlu et al., 2024).

For me, I just know I feel good when I have my morning glass. It's lovely to see the science catching up with what people have known for centuries.

How I enjoy mine

• A small glass (about 200 to 250 ml) in the morning, straight from the fridge, cold and tangy
• Blended with banana and a bit of honey for a smoothie
• Instead of buttermilk in my baking, or poured over oats the night before
• Whisked into a salad dressing with garlic and herbs

If you'd like to try it yourself, our Milk Kefir Starter Kit has everything you need: fresh grains, a 3 L glass jar, a sieve, a spatula and a cheesecloth. Or just get the fresh kefir grains if you already have a jar at home. Near Bela-Bela? Come buy fresh kefir straight from us.

Please chat to your doctor or healthcare professional before making big changes to your diet, especially if you have a health condition or a weakened immune system.

References

Choi, Y. (2025). Evaluation of kefir consumption on gut microbial diversity in healthy adults. Frontiers in Microbiology, 16, 1587831.

Çıtar Dazıroğlu, M. E., Acar Tek, N., Cevher Akdulum, M. F., Yılmaz, C., & Yalınay, A. M. (2024). Effects of kefir consumption on gut microbiota and health outcomes in women with polycystic ovary syndrome. Food Science & Nutrition, 12(8), 5632–5646. https://doi.org/10.1002/fsn3.4212

Prado, M. R., Blandón, L. M., Vandenberghe, L. P. S., Rodrigues, C., Castro, G. R., Thomaz-Soccol, V., & Soccol, C. R. (2015). Milk kefir: composition, microbial cultures, biological activities, and related products. Frontiers in Microbiology, 6, 1177. https://doi.org/10.3389/fmicb.2015.01177

Sindi, A., Badsha, M. B., & Ünlü, G. (2020). Bacterial populations in international artisanal kefirs. Microorganisms, 8(9), 1318. https://doi.org/10.3390/microorganisms8091318