Kefir is a fermented milk drink made with live cultures, and people have enjoyed it for a very long time. The research on what it does for people is still limited, so we do not make health claims for it. Here is what the studies say, and how much weight they can carry.
What the research says
- Much of the early evidence comes from labs and animals. A 2017 review of milk kefir noted that a large share of the studies behind its reputation were done in test tubes or in animals, and called for proper clinical trials in people.
- Trials in people are few, small and mixed. A 2023 systematic review of randomised trials found 16 studies. Twelve of them had a high risk of bias, and safety was measured in only five of the 18 papers. The authors concluded that kefir appears safe for generally healthy people, but that high-quality trials are needed before any recommendation is made.
- Lactose. A small 2003 study gave 15 adults who digest lactose poorly equal amounts of lactose in milk, yogurt and kefir. Breath tests suggested the lactose in kefir was digested more easily than the lactose in milk. It is one small study, and its authors asked for more.
- Blood pressure. A 2025 analysis of seven trials with 385 adults found that kefir made no significant difference to blood pressure.
Is kefir a probiotic?
It depends what you mean by the word. The US National Center for Complementary and Integrative Health describes probiotics as live microorganisms that are intended to have health benefits when consumed. An international expert panel (ISAPP) defines fermented foods by how they are made, through desired microbial growth, and treats them as a separate category from probiotics. Kefir is a fermented food that contains live cultures, and that is how we describe it on our product pages.
What about immunity, weight loss or detox?
You may read that kefir boosts immunity, melts fat or detoxifies the body. We have not found good trials in people that show this, so we do not say it, and we do not say it about any other product we sell either.
So why drink kefir?
Because it tastes good, it is easy to make at home, and a small glass can be part of an ordinary, balanced diet. That is all we claim.
Good to know
- Milk kefir is a dairy food, so it contains milk protein and lactose. Water kefir has no dairy.
- Kefir is tangier than yogurt. A small glass is the best way to start.
- Research on kefir is still limited. For advice about your own health, ask your doctor.
Want to make your own? Start with How to make milk kefir at home and Live Milk Kefir Grains.
Sources: Rosa et al. 2017, Nutrition Research Reviews, Milk kefir: nutritional, microbiological and health benefits; Kairey et al. 2023, Nutrition Reviews, The effects of kefir consumption on human health: a systematic review of randomized controlled trials; Hertzler and Clancy 2003, Kefir improves lactose digestion and tolerance in adults with lactose maldigestion; Rashidbeygi et al. 2025, The effect of kefir consumption on blood pressure and C-reactive protein; Marco et al. 2021, ISAPP consensus statement on fermented foods; National Center for Complementary and Integrative Health, Probiotics: usefulness and safety. All opened 10 October 2026. Written by KefirBuy.
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