Health & Well-Being A-Z


bowl of kefir grains

Kefir is a probiotic drink made by fermenting milk.

Kefir is used for obesity, athletic performance, osteoporosis, high cholesterol, and many other conditions, but there is no good scientific evidence to support these uses.

Is It Effective?

Effectiveness header

NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

Insufficient evidence
  • Diarrhea in people taking antibiotics (antibiotic-associated diarrhea). Some research shows that a kefir-containing drink does not reduce diarrhea caused by antibiotics in children.
  • Athletic performance. Early research shows that taking kefir after exercise does not improve running speed.
  • Nausea and vomiting caused by cancer drug treatment. Early research shows that taking kefir during chemotherapy treatment does not reduce stomach and intestinal problems. In fact, it might make these problems slightly worse.
  • Constipation. Early research shows that taking kefir helps increase the number of bowel movements in people with constipation. It also seems to soften stools.
  • A type of inflammatory bowel disease (Crohn disease). Early research shows that taking kefir might help with some symptoms of Crohn disease.
  • A digestive tract infection that can lead to ulcers (Helicobacter pylori or H. pylori). Early research shows that taking kefir along with standard treatment for H. pylori helps get rid of infections in more people than standard treatment alone.
  • High cholesterol. Early research shows that taking kefir does not lower cholesterol levels.
  • Symptoms of menopause. Early research shows that taking kefir might help with some symptoms of menopause, especially sleep.
  • A grouping of symptoms that increase the risk of diabetes, heart disease, and stroke (metabolic syndrome). Early research shows that taking kefir does not reduce blood pressure, cholesterol levels, or blood sugar in people with metabolic syndrome.
  • Obesity. Early research shows that eating kefir as part of a weight maintenance diet reduces body weight by a small amount in overweight or obese women. But eating low-fat milk dairy products instead of kefir seems to work just as well.
  • Swelling (inflammation) and sores inside the mouth (oral mucositis). Early research shows that rinsing the mouth with kefir and swallowing 250 mL of kefir twice daily for the first 5 days of chemotherapy does not prevent the development of sores inside the mouth caused by chemotherapy.
  • Weak and brittle bones (osteoporosis). Early research shows that taking kefir with calcium does not improve bone strength any more than calcium alone in adults with osteoporosis.
  • A type of inflammatory bowel disease (ulcerative colitis). Early research shows that taking kefir does not improve symptoms of ulcerative colitis.
  • Lactose intolerance.
  • Improving digestion.
  • Other conditions.

More evidence is needed to rate the effectiveness of kefir for these uses.

Is it Safe?


Kefir contains actively growing bacteria and yeast. Their effect on milk results in production of enzymes and chemicals that affect the way food is digested.


When taken by mouth: Kefir is POSSIBLY SAFE for most adults when taken for up to 12 weeks. Kefir can cause side effects like bloating, nausea, intestinal cramping, and constipation, especially when first started. These side effects usually stop with continued use.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn't enough reliable information to know if kefir is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.

Children: Kefir is POSSIBLY SAFE for children between the ages of 1 and 5 years when taken by mouth for up to 10 days.

AIDS and other conditions that weaken the immune system: Kefir contains actively growing bacteria and yeast. There is some concern that people with a weakened immune system might be more likely to develop infections from these bacteria or yeast.

Colon cancer: In people undergoing chemotherapy for colon cancer, kefir might increase side effects such as stomach and intestinal problems, mouth sores, drowsiness, sweats, and hair loss.

Drug interactions

Disulfiram (Antabuse)

Interaction Rating=Minor Be watchful with this combination.

Kefir might contain alcohol. The body breaks down alcohol to get rid of it. Disulfiram (Antabuse) decreases the break-down of alcohol. Taking kefir along with disulfiram (Antabuse) can cause a pounding headache, vomiting, flushing, and other unpleasant reactions. Don't drink any alcohol if you are taking disulfiram (Antabuse).

Medications that decrease the immune system (Immunosuppressants)

Interaction Rating=Moderate Be cautious with this combination.

Kefir contains live bacteria and yeast. The immune system usually controls bacteria and yeast in the body to prevent infections. Medications that decrease the immune system can increase your chances of getting sick from bacteria and yeast. Taking kefir along with medications that decrease the immune system might increase the chances of getting sick.

Some medications that decrease the immune system include azathioprine (Imuran), basiliximab (Simulect), cyclosporine (Neoral, Sandimmune), daclizumab (Zenapax), muromonab-CD3 (OKT3, Orthoclone OKT3), mycophenolate (CellCept), tacrolimus (FK506, Prograf), sirolimus (Rapamune), prednisone (Deltasone, Orasone), corticosteroids (glucocorticoids), and others.

Herb interactions

There are no known interactions with herbs and supplements.

Food interactions

There are no known interactions with foods.


The appropriate dose of kefir depends on several factors such as the user's age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for kefir. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

Other names

Fermented Dairy Product, Fermented Milk, Fromage Kéfir, Kéfir, Kefir Cheese, Kefir Grains, Kefir Yogurt, Kellermilch, Kjaklder Mjoklk, Lait Fermenté, Omaere, Produit Laitier Fermenté, Rob, Roba, Tarag.


Information on this website is for informational use only and is not intended to replace professional medical advice, diagnosis, or treatment. While evidence-based, it is not guaranteed to be error-free and is not intended to meet any particular user’s needs or requirements or to cover all possible uses, safety concerns, interactions, outcomes, or adverse effects. Always check with your doctor or other medical professional before making healthcare decisions (including taking any medication) and do not delay or disregard seeking medical advice or treatment based on any information displayed on this website.

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