Kefir contains several bacterial and yeast species that may interact with the intestinal microbiome.

Research has identified microorganisms belonging to the following groups in traditional kefir:

• Lactobacillus

• Lactococcus

• Leuconostoc

• Acetobacter

• Various yeast species

Some of these microorganisms produce organic acids and antimicrobial compounds that may inhibit the growth of certain undesirable bacteria under laboratory conditions.

For example, kefir contains lactic acid, which contributes to its acidic environment. Certain bacterial strains also produce bacteriocins and other substances that may interfere with the growth of competing microorganisms.

These properties have attracted attention because harmful microorganisms can contribute to gastrointestinal infections and digestive disturbances.

Research published in Frontiers in Microbiology has examined the antimicrobial activities of kefir microorganisms and their potential applications in digestive health.

However, it would be inaccurate to assume that drinking kefir can prevent or cure infections caused by organisms such as Salmonella, Escherichia coli, or Giardia. Laboratory antimicrobial activity does not automatically translate into an effective treatment in humans.

Nevertheless, consuming kefir as part of a varied diet may help increase exposure to beneficial microorganisms.

Why this matters: Maintaining a healthy gut microbiome is important for normal digestive function. Kefir offers one convenient way to introduce live microorganisms through food.

2. Kefir May Help Relieve Constipation

Constipation is a common digestive complaint characterized by infrequent bowel movements, hard stools, straining, or the feeling that the bowel has not emptied completely.

It can be influenced by several factors, including insufficient dietary fiber, inadequate fluid intake, limited physical activity, changes in routine, and certain medications.

Because kefir contains live microorganisms, researchers have investigated whether fermented milk products can support regular bowel movements.

Certain probiotic bacteria may influence intestinal motility, stool consistency, and the production of compounds involved in normal digestive function.

Some probiotic strains can also influence the metabolism of dietary carbohydrates and the production of short-chain fatty acids, which are important for the health of the intestinal environment.

A small clinical study published in the Turkish Journal of Gastroenterology investigated the effects of kefir consumption in people experiencing constipation. The researchers reported improvements in certain bowel-related measures following regular consumption.

However, studies involving kefir and constipation have generally been small, and results cannot be generalized to everyone.

Kefir should also not be considered a replacement for adequate fiber intake.

If you experience constipation, you may benefit from combining fermented foods with fiber-rich ingredients such as:

• Oats and whole grains.

• Apples, pears, and berries.

• Prunes and other dried fruits.

• Beans and lentils.

• Leafy green vegetables.

• Chia seeds and flaxseeds.

Drinking sufficient water and staying physically active are also important.

Practical tip: Try adding plain kefir to an oatmeal breakfast with berries and chia seeds. This combination provides protein, beneficial microorganisms, and dietary fiber, all of which can contribute to a healthier digestive routine.

Persistent constipation, particularly when accompanied by abdominal pain, blood in the stool, unexplained weight loss, or a sudden change in bowel habits, should be evaluated by a healthcare professional.

3. Kefir May Be Easier to Digest for People With Lactose Intolerance

Lactose intolerance occurs when the small intestine does not produce enough lactase, the enzyme responsible for breaking down lactose.

Lactose is the natural sugar found in milk and many dairy products.

When someone with lactose intolerance consumes more lactose than their digestive system can comfortably process, the undigested sugar travels into the large intestine. There, intestinal bacteria ferment it, producing gas and attracting water into the bowel.

This can cause symptoms such as:

• Abdominal bloating.

• Excessive gas.

• Stomach cramps.

• Diarrhea.

• Abdominal discomfort.

• Occasionally, nausea.

One interesting characteristic of kefir is that its fermentation process reduces the lactose content of milk.

The bacteria and yeasts in kefir grains use lactose during fermentation. Some microorganisms also produce beta-galactosidase, an enzyme that helps break down lactose.

As a result, fermented kefir is often better tolerated than ordinary milk by people with lactose intolerance.

Research published in the Journal of the American Dietetic Association and other scientific publications has investigated the relationship between fermented dairy products and lactose digestion.

The findings suggest that certain live cultures in fermented dairy foods can improve lactose digestion and reduce digestive symptoms in people with lactose malabsorption.

However, not every kefir product contains the same amount of remaining lactose, and individual tolerance varies.

Kefir is therefore not guaranteed to be completely symptom-free for everyone.

If you have lactose intolerance, consider the following precautions:

1. Start with a small serving, such as a few tablespoons.

2. Consume kefir alongside a meal rather than drinking a large amount on an empty stomach.

3. Monitor your digestive response over several days.

4. Choose plain kefir without excessive added sugar.

5. Look for certified lactose-free products if even small quantities cause symptoms.

It is particularly important to distinguish lactose intolerance from milk allergy. People with a milk protein allergy can still react to fermented dairy products and should not assume that kefir is safe simply because it contains less lactose.

4. Kefir May Support Immune System Function

Your digestive system and immune system are closely connected.

A large proportion of the body's immune activity is associated with tissues surrounding the gastrointestinal tract. The microorganisms living in the intestines also interact with immune cells and help regulate responses to different substances.

This is one reason scientists are interested in the potential relationship between probiotics and immune health.

Kefir contains bacteria and yeasts that may influence the intestinal environment and interact with the body's natural defense mechanisms.

Certain microorganisms found in kefir can produce substances that inhibit competing microbes. Others may influence the activity of immune cells and the production of signaling molecules involved in immune regulation.

One particularly interesting microorganism is Lactobacillus kefiri, which has been investigated for its antimicrobial and immunomodulatory properties.

Research published in Frontiers in Microbiology has examined the biological activities of this species and its possible contribution to the protective properties of kefir.

However, immune system regulation is complicated. More immune activity is not necessarily better, because excessive inflammatory responses can also damage healthy tissues.

The goal is to maintain an appropriately balanced immune response.

A review of randomized controlled trials published in Nutrition Reviews in 2023 found that the evidence supporting specific health benefits of kefir remains limited. Therefore, kefir should be considered a potentially useful component of a healthy diet rather than a proven immune treatment.

You can support your immune system by combining kefir consumption with other healthy habits:

• Eat a variety of fruits and vegetables.

• Include sufficient protein in your diet.

• Get adequate sleep.

• Exercise regularly.

• Avoid smoking.

• Maintain good food hygiene.

• Manage chronic stress.

• Stay up to date with recommended vaccinations.

The takeaway: Kefir may support the gut environment involved in immune regulation, but it cannot guarantee protection against infections or replace medical care.

5. Kefir May Help Improve Blood Sugar Regulation

Blood sugar regulation is an important part of metabolic health.