Kefir

Food · Dairy · Food, Typed Supps

A fermented dairy drink with far more strain variety than most yogurt.

Stage by stage

Intake (Already fermented): Already partially fermented by a diverse culture of bacteria and yeast.
Stomach (Cultures survive acid): Some live cultures begin surviving the acidic environment better than typical yogurt cultures.
Small & large intestine (Reaches the gut): Surviving cultures reach the gut, interacting with existing gut flora.
Gut (Broad strain diversity): A broader range of bacterial and yeast strains than standard yogurt interacts with the gut environment.

Timing

Often consumed on its own like a drink.

Time to effect

Days: Any reported digestive effect in studies.

Allergens

Contains: Milk. Derived from what this food is, not from a product label.

Eating patterns

Fits: Vegetarian, Pescatarian, Halal, Kosher, Keto, Gluten-free.

Satiety

The satiety index is measured on 240 kcal servings. At 41 kcal per 100 g that is 585 g of this, which is not a serving anyone eats — so the index has nothing to say about it.

Environmental footprint

3.2 kg CO2e and 628 litres of freshwater per kg, matched to "Milk" in Poore & Nemecek (2018), Science 360.

Cost band

Cheap — roughly £2.5 per kg, as a band midpoint rather than a price.

Key nutrients

Live cultures (diverse)
Protein
Calcium

Nutrition per 100g

Calories: 41
Protein: 3.8g
Carbohydrate: 4.8g
of which sugars: 4.8g
Fat: 1g
of which saturated: 0.6g
Fibre: 0g
Sodium: 40mg

Food vs. supplement

Kefir typically contains a wider variety of bacterial and yeast strains than yogurt or a standard probiotic supplement — though, like yogurt, the exact strain count and survival rate varies significantly by brand.

Kitchen tip

A few tablespoons of an existing batch can be used to start a new one, since the live cultures keep multiplying.

Common myth

“Kefir and yogurt are basically the same thing.” In reality: Kefir’s fermentation involves a more diverse mix of bacteria and yeast than yogurt’s typically limited set of cultures.