Glass of milk kefir with a jar of kefir grains

Kefir Benefits: What the Evidence Shows

ByCraig Brockie Last updated

What kefir is

Kefir is a tart, drinkable fermented milk. Traditional kefir is made by adding kefir grains to milk. These aren’t cereal grains: they are small, rubbery clusters of protein and polysaccharide that hold a community of lactic acid bacteria and yeasts, according to a 2016 review in Frontiers in Microbiology.

The yeasts are what set kefir apart from yogurt. Fermentation leaves kefir slightly viscous and acidic, with low levels of alcohol and sometimes a light fizz, and the bacterial mix usually includes Lactobacillus, Lactococcus, Streptococcus and Leuconostoc species.

Most store-bought kefir isn’t made with grains. The same review notes that commercial producers usually use starter cultures isolated from kefir grains for a more consistent product, and that research on the benefits of industrially made kefir is largely missing. Keep that in mind when reading the studies below: the kefir in a trial may not match the bottle in your fridge. For other fermented options, see fermented foods for gut health.

Kefir nutrition per cup

NutrientPer 1 cup (243 g) low-fat plain kefir
Calories104
Protein9.2 g
Fat2.5 g
Carbohydrate11.6 g
Total sugars (mostly lactose)11.2 g
Lactose9.0 g
Calcium316 mg
Potassium399 mg
Vitamin D2.4 mcg
Vitamin B120.7 mcg
Sodium97 mg

These figures come from the USDA FoodData Central entry for low-fat plain kefir, which is based on one brand (Lifeway). Whole-milk and flavored kefirs differ, and vitamin D depends on whether the maker fortifies. The 316 mg of calcium is about a quarter of the 1,300 mg Daily Value.

Kefir benefits: what human studies show

The best overview is a 2023 systematic review of 16 randomized trials (18 publications). It concluded that kefir appears safe for generally healthy people, but 12 of the 16 studies had a high overall risk of bias, safety was assessed in only 5 publications, and the authors said better trials are needed before any recommendations can be made.

Lactose digestion

This is the clearest benefit: in a 2003 trial by Hertzler and Clancy, 15 adults with lactose maldigestion drank servings of milk, kefir or yogurt that each held 20 g of lactose. Plain kefir produced about 60% less breath hydrogen, a marker of undigested lactose, than milk did, and kefir and yogurt both cut how severe people rated their gas by 54% to 71%. Flavored kefir did less well than plain. The study was small and short, so treat the result as encouraging rather than settled.

Blood sugar and insulin

A 2021 meta-analysis of six trials (323 people) found that kefir lowered fasting blood sugar and insulin, with no significant change in HbA1c, the longer-term marker. A 2023 meta-analysis of six trials (314 people) found lower fasting insulin and insulin resistance, but no effect on fasting blood sugar or HbA1c.

One of the key trials, a 2015 study of 60 people with type 2 diabetes, gave 600 mL a day for 8 weeks of a fermented milk containing Lactobacillus casei, Lactobacillus acidophilus and bifidobacteria, so it was closer to a probiotic drink than traditional grain kefir. Taken together, kefir may help insulin levels modestly, but the results are mixed and the trials are small.

Cholesterol and blood pressure

The 2023 meta-analysis found no effect on total, LDL or HDL cholesterol, triglycerides or body weight. An earlier crossover trial in 13 men with mildly high cholesterol found no change in blood lipids after 4 weeks of kefir compared with milk.

For blood pressure, a 2025 meta-analysis of seven trials (385 adults) found no significant change in systolic or diastolic pressure or in C-reactive protein, an inflammation marker. CRP did fall in the subgroup of trials lasting 8 weeks or longer, so the authors said long-term intake may improve CRP, a finding that still needs confirming.

H. pylori treatment, as an add-on

In a 2011 randomized, double-blind trial of 82 people with Helicobacter pylori infection, all patients took a standard 14-day course of three medicines. Those who also drank 250 mL of kefir twice a day cleared the infection more often (78% vs 50% with a placebo milk) and reported fewer and milder side effects. It is a single, fairly small trial, and kefir was used alongside prescribed treatment, never in place of it.

What the evidence doesn’t support

  • Lowering cholesterol or blood pressure: pooled trials show no significant effect so far.
  • Weight loss: the 2023 meta-analysis found no effect on body weight.
  • Treating infections or disease on its own: the H. pylori result applies only to kefir taken with medical treatment.
  • Cancer, wound healing and allergy claims: reviews such as Bourrie and colleagues list these, but much of the support comes from lab and animal studies, not human trials.

Who should be careful

  • People with weakened immune systems or serious illness. NCCIH says the risk of harmful effects from probiotics is greater in these groups. Kefir is a food full of live microbes, so ask your care team before adding it.
  • People avoiding alcohol completely. Kefir contains low levels of alcohol from yeast fermentation. Grain-fermented batches, including homemade kefir, vary more, which is one reason commercial makers use defined starter cultures.
  • People with lactose intolerance. Kefir is easier on many people than milk, but it is not lactose-free: the USDA entry lists about 9 g per cup.
  • People with a milk allergy. Dairy kefir contains milk proteins.

For a fuller list of side effects and risks, read dangers of kefir. This article is general information, not medical advice.

How to choose kefir and how much to drink

Small glass of kefir with breakfast oats
  • Start with plain. Flavored kefirs often add sugar; check the Added Sugars line on the Nutrition Facts panel.
  • Read the culture list. Labels that name the bacteria and yeasts tell you more than a generic “probiotic” claim.
  • Pick the fat level you prefer. Whole-milk kefir is richer; low-fat has fewer calories per cup.
  • Compare brands by label, not marketing. Our best kefir brands guide compares published labels.

Research has not settled on an ideal amount. The trials above used 250 mL (about 1 cup) twice a day or 600 mL a day. A practical start is a small glass a day, building to about a cup if your stomach handles it well. For ideas on fitting it in, see how to drink kefir or blend it into a kefir smoothie.

Related topics

Sources

Craig Brockie is the founder of Ultimate Health Solutions, the company behind Ultimate Gut, and the author of Ultimate Health, The Ultimate Gut Health Guide and The Unlimited Probiotics Guide. After injuries and chronic health problems in his twenties that conventional care didn’t resolve, he began researching health on his own and has studied natural health for 30 years. He is not a medical professional, and his articles are general information, not medical advice.

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