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Kefir

Also known as Milk kefir, Kefir drink

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Milk fermented with kefir grains, a rubbery symbiotic matrix of bacteria and yeasts that is strained out and reused. The yeast component makes it slightly effervescent and gives it a broader microbial mix than yogurt.

Gut & Digestive HealthImmune Health

Potential health benefits

Best supported: Moderate

Ordered by how well the human research supports them — strongest first. A rating describes the state of the evidence, not how impressive the food is. How we rate evidence.

Digestive comfort

Gut & Digestive Health
Moderate evidence

Some trials report that kefir improves lactose digestion and reduces associated symptoms, similar to yogurt. The kefir-specific trial base is smaller than the yogurt one.

Moderate evidence. Several human studies point the same way, with real caveats.

4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Gut microbiome

Gut & Digestive Health
Limited evidence

Some trials report shifts in gut microbial composition during regular kefir intake. Effects are modest, differ between products and people, and generally fade after intake stops.

Limited evidence. Early human work, or mostly lab and animal research.

3 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Immune function

Immune Health
Insufficient evidence

Evidence is limited for kefir affecting immune function in humans. Much of what is cited comes from cell and animal work, and the few human trials are small with markers rather than infection outcomes.

Insufficient evidence. Not enough human research to say anything useful yet.

4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Ask about Kefir

Ask about Kefir

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Key nutrients

Nutrient content per 100 grams
NutrientAmount% DV
Macronutrients
Calories43 kcal2%
Protein3.79 g8%
Total fat1.02 g1%
Carbohydrate4.77 g2%
Fibre0 g0%
Total sugars4.61 g—
Water89.7 g—
Fats
Saturated fat0.658 g3%
Monounsaturated fat0.31 g—
Polyunsaturated fat0.053 g—
Cholesterol5 mg2%
ALA (omega-3)0.0060 g—
EPA (omega-3)0 g—
DHA (omega-3)0 g—
DPA (omega-3)0.0010 g—
Linoleic acid (omega-6)0.042 g—
Vitamins
Vitamin A171 µg19%
Vitamin C0.2 mg0%
Vitamin D1 µg5%
Vitamin E0.02 mg0%
Vitamin K0.1 µg0%
Thiamin (B1)0.03 mg3%
Riboflavin (B2)0.135 mg10%
Niacin (B3)0.15 mg1%
Pantothenic acid (B5)0.385 mg8%
Vitamin B60.058 mg3%
Folate13 µg3%
Vitamin B120.29 µg12%
Choline15.2 mg3%
Minerals
Calcium130 mg10%
Iron0.04 mg0%
Magnesium12 mg3%
Phosphorus105 mg8%
Potassium164 mg3%
Sodium40 mg2%
Zinc0.46 mg4%
Copper0.0090 mg1%
Manganese0.0050 mg0%
Selenium3.6 µg7%
Other measured compounds
Beta-carotene0 µg—
Alpha-carotene0 µg—
Lycopene0 µg—
Lutein + zeaxanthin0 µg—
Caffeine0 mg—
Ash0.72 g—

Nutrient values are per 100 g of the USDA reference entry named on this page and vary with variety, growing conditions, storage and preparation.

Source record: Kefir, lowfat, plain, LIFEWAY (USDA FoodData Central, FDC ID 170904).

% DV uses the FDA Daily Values for adults and children aged 4 and over. A dash means no Daily Value has been established for that nutrient.

Bioactive compounds

Compounds present in meaningful amounts. Presence is banded rather than quantified, because whole-food levels vary enormously with variety, growing conditions, storage and preparation.

How preparation changes things

Only effects with real support are listed. If a preparation method is missing, it is because nothing dependable is documented — not because it makes no difference.

  • fermentedReduces lactose

    Kefir fermentation consumes part of the lactose and supplies bacterial lactase, and small trials suggest it is tolerated similarly to yogurt by people with lactose maldigestion.

Things to know

Allergies, interactions and intake concerns. Every food gets this section — a reference where everything is uniformly good is not a reference.

  • Allergy

    Cow milk protein allergy

    Milk kefir carries milk proteins and is unsafe in cow milk protein allergy. Water kefir is a different product entirely.

  • Worth knowing

    Live cultures and immunosuppression

    Kefir contains live yeasts as well as bacteria. Invasive infection from probiotic organisms is rare but documented in severely immunocompromised patients, and clinical advice applies there.

  • Worth knowing

    Trace alcohol from yeast fermentation

    Yeast activity produces small amounts of ethanol, typically well under one percent but higher in long home fermentations. Worth knowing for anyone avoiding alcohol entirely.

  • Worth knowing

    Highly variable microbial content

    Grain-fermented home kefir and commercial kefir made from a defined starter differ substantially in which organisms they contain and in what quantity.