Kefir and yogurt are both fermented milks, and nutritionally they’re close. The real differences are in how they’re made and what lives in them: yogurt is set by two heat-loving bacteria, while kefir is fermented at room temperature by “grains” that hold a whole community of bacteria and yeasts. Kefir is drinkable and slightly fizzy; yogurt is spoonable. Both are easier on lactose than milk.
How They’re Made
- Yogurt is milk fermented with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus at around 43°C for a few hours. In the US, a product can only be called yogurt if it’s cultured with these two bacteria (21 CFR 131.200); many brands add other strains.
- Kefir is made by adding kefir grains – clumps of lactic acid bacteria and yeasts held together in a matrix of polysaccharide and protein – to milk at room temperature for about a day. For the method, see how to make milk kefir at home. The grains carry a more varied mix of microbes than yogurt cultures, including yeasts, which is why kefir is slightly fizzy and can contain a trace of alcohol (Bourrie et al., 2016). Many store-bought kefirs are made with defined cultures rather than grains.
Nutrition Per 100 g
| Plain low-fat kefir | Plain whole-milk yogurt | Plain whole-milk Greek yogurt | |
|---|---|---|---|
| Energy | 43 kcal | 61 kcal | – |
| Protein | 3.8 g | 3.5 g | 8.8 g |
| Fat | 1.0 g | 3.3 g | 4.4 g |
| Carbohydrate | 4.8 g | 4.7 g | 4.8 g |
| Calcium | 130 mg | 121 mg | 111 mg |
Sources: USDA FoodData Central (kefir, yogurt, Greek yogurt). Plain kefir and plain yogurt are almost the same; the fat depends on the milk used. Strained Greek yogurt has more than twice the protein per spoonful.
Which Is Better for Lactose Intolerance?
Both help. In a randomized study of 15 adults who digest lactose poorly, each given the same 20 g of lactose as milk, plain kefir or plain yogurt, breath hydrogen – a marker of undigested lactose – was about three times higher after milk than after either kefir or yogurt, and kefir and yogurt both reduced flatulence severity compared with milk (Hertzler & Clancy, 2003). The European Food Safety Authority accepts that live yogurt cultures improve lactose digestion (EFSA, 2010). Neither is “lactose-free”; people with a milk allergy should avoid both.
Health Claims: What the Evidence Shows
Kefir is often promoted for gut, heart and metabolic health. A systematic review of 16 randomized trials found it may help with a few things – such as reducing Streptococcus mutans in the mouth and as an add-on in H. pylori treatment – but the evidence was very limited and most studies were at high risk of bias (Kairey et al., 2023). So choose by taste, texture and how you’ll use it: kefir for drinking and smoothies, yogurt for spooning, cooking and straining into labneh.
Go further: make yogurt at home, compare kefir brands and yogurts with live cultures, or see how long kefir lasts.
