What are the side effects of drinking kefir milk?

December 22, 2025 •

4 min read

While celebrated for its probiotic content, kefir milk can cause digestive side effects such as gas, bloating, and stomach cramps, especially when first introduced to your diet. These temporary symptoms typically subside as your body adjusts to the influx of new bacteria.

Quick Summary

Kefir milk can cause temporary digestive discomfort like bloating, gas, and cramps due to its potent probiotics. Certain individuals, including those with milk allergies, weakened immune systems, or histamine intolerance, should exercise caution or avoid it. Gradually introducing kefir and choosing plain, unsweetened varieties can help minimize adverse effects.

Key Points

Initial Digestive Discomfort: When starting, temporary side effects like bloating, gas, stomach cramps, and changes in bowel movements are common and typically subside as your gut adapts.
Immune System Considerations: Individuals with weakened immune systems or conditions like HIV should consult a doctor before consuming kefir due to the active live cultures.
Milk Allergies: People with a true milk (casein) allergy must avoid dairy-based kefir entirely; non-dairy alternatives exist for these individuals.
Lactose Tolerance: Kefir contains less lactose than milk, making it often tolerable for those with lactose intolerance, but those with high sensitivity may still react.
Manage with Gradual Intake: To minimize side effects, start with a small amount of kefir and increase your intake slowly over time as your body adjusts.
Plain vs. Flavored: Unsweetened, plain kefir is recommended, as added sugars in flavored varieties can worsen digestive issues.
Contains Trace Alcohol: A small amount of alcohol is naturally produced during fermentation, which may be a factor for children, recovering alcoholics, or those with sensitivities.
Histamine Intolerance: As a fermented food, kefir is high in histamine and may trigger reactions like headaches or digestive upset in sensitive individuals.

Common Digestive Side Effects of Kefir

For most people, kefir is a healthy addition to their diet, but its high concentration of probiotics can sometimes lead to uncomfortable side effects, particularly during the initial phase of consumption.

Bloating and gas: When you first introduce kefir, the sudden influx of new bacteria into your gut microbiome can lead to increased gas and a feeling of fullness. This is a common and usually temporary symptom as your body adjusts.
Stomach cramps and discomfort: In some cases, the change in gut flora can cause mild stomach cramping or a general feeling of unease. This can also be part of the adjustment period.
Changes in bowel movements: Some people may experience either temporary diarrhea or constipation as their digestive system adapts. These symptoms should resolve with continued, consistent use.
Nausea: A smaller number of individuals may feel nauseous after drinking kefir, especially if consumed on an empty stomach or in large amounts.

Serious Concerns and Who Should Be Cautious

While typically mild, some side effects warrant more attention, and certain populations should be cautious about consuming kefir.

Weakened Immune Systems

Kefir contains living, active bacteria and yeast cultures. While safe for most, people with compromised immune systems—such as those with HIV or undergoing chemotherapy—are at a higher risk of developing infections from these microorganisms. It is crucial for these individuals to consult a doctor before adding kefir to their diet.

Milk Allergies and Lactose Intolerance

Individuals with a true milk allergy (a reaction to casein protein) must avoid traditional dairy-based kefir, as it can cause severe allergic reactions. However, many people with lactose intolerance can tolerate kefir because the fermentation process significantly reduces the lactose content. For those with severe lactose intolerance, dairy-free alternatives like coconut milk or water kefir are available.

Histamine Intolerance

As a fermented food, kefir is naturally high in histamines. For people with histamine intolerance, this can trigger a variety of symptoms, including headaches, digestive issues, and skin irritation.

Reducing and Managing Kefir Side Effects

To minimize potential side effects and help your body adapt, consider these strategies:

Start with a small dose: Begin with just a few tablespoons a day and gradually increase the amount over a week or two. This gives your digestive system time to adjust.
Stay consistent: Regular, daily consumption helps stabilize your gut microbiome. Consistent intake is often more effective and better tolerated than sporadic large doses.
Choose plain, unsweetened kefir: Avoid varieties with added sugars or artificial sweeteners, which can feed harmful bacteria and exacerbate digestive upset.
Consider dairy-free options: If digestive issues persist, switching to a water kefir or coconut milk kefir can eliminate the potential side effects associated with dairy.

Comparison of Kefir Types and Their Potential Side Effects

To help you decide which type is right for you, here is a comparison of traditional and alternative kefirs based on common side effect concerns.


Feature	Dairy Milk Kefir	Water Kefir	Coconut Milk Kefir
Best for Lactose Intolerance?	Often tolerable due to reduced lactose, but not guaranteed.	Yes, completely lactose-free.	Yes, lactose-free option.
Alcohol Content	Minimal, typically less than 1%.	Minimal, usually less than 0.5% ABV.	Minimal, fermentation produces small amounts.
Nutrient Profile	Rich in calcium, protein, and B vitamins.	Varies, typically lower in protein and fat.	Varies based on base milk; may lack dairy nutrients.
Taste Profile	Tangy, creamy, and slightly effervescent.	Sweet and tangy, often like a fruit soda.	Creamy, slightly tangy; taste depends on base.
Best to avoid if...	You have a true dairy allergy or weakened immunity.	You need a high-protein option or monitor sugar.	You need a high-protein option or have a coconut allergy.

Water Kefir and Coconut Milk Kefir

For those sensitive to dairy, water kefir and coconut milk kefir are excellent non-dairy alternatives. They still offer a powerful dose of probiotics to support gut health but without the lactose or casein proteins found in milk kefir. However, some water kefirs may contain added sugars, so it's important to read the label if you are managing blood sugar.

Conclusion: Listening to Your Body is Key

Kefir is a potent probiotic source with many potential health benefits, but understanding its side effects is crucial for a positive experience. The initial digestive upset, such as bloating and gas, is a normal and temporary reaction for many people as their gut adjusts. However, individuals with weakened immune systems, true milk allergies, or histamine intolerance should approach with caution or opt for non-dairy alternatives after consulting a healthcare provider. The key to minimizing side effects is to start slow, stay consistent, and listen to your body’s unique response. By finding the right type and dosage, most people can successfully incorporate this fermented drink into their routine and enjoy its full health-boosting potential. A 2025 study in Frontiers in Microbiology underscores kefir's potential to positively modulate gut microbiota in healthy individuals, reinforcing its value when consumed appropriately.

Frequently Asked Questions

Yes, it is common to experience mild bloating, gas, or stomach discomfort when you first start drinking kefir. This is a normal reaction as your gut microbiome adjusts to the influx of new probiotic bacteria and typically subsides with consistent use.

Temporary side effects, such as gas and bloating, usually resolve within a few days to a couple of weeks as your body gets used to the new probiotics. If symptoms persist or worsen, consider reducing your intake or consulting a doctor.

Many people with lactose intolerance can drink kefir without issues. The fermentation process breaks down much of the lactose. However, if you are very sensitive, opt for non-dairy water kefir or coconut milk kefir instead.

People with severely weakened immune systems (e.g., due to chemotherapy or HIV), a milk allergy, or histamine intolerance should be cautious or avoid drinking kefir and consult a healthcare provider.

In some individuals, particularly during the initial phase of introduction, kefir may cause temporary constipation or diarrhea as the gut adapts. These effects are usually transient and improve with continued use.

Yes, due to the natural fermentation process, kefir contains a small amount of alcohol, typically between 0.5% and 2%. Most commercial brands have very low levels, but individuals who avoid alcohol should be aware.

Start with a very small amount (1-2 tablespoons) per day and gradually increase your intake. Choosing a plain, unsweetened variety can also help minimize potential issues.