Kefir 101: Nutrition Facts, Health Benefits, and Side Effects

Kefir is a type of cultured dairy drink made by fermenting milk with kefir grains.

Although records of this drink date back thousands of years, kefir has experienced a recent renaissance in the Western world.

With people viewing it as a healthy source of beneficial probiotics, kefir has quickly become a commercial success.

This article examines kefir’s nutrition facts, potential health benefits, and side effects.

What Is Kefir?

Homemade Milk Kefir Grains and Glass of Kefir.

Kefir (pronounced kuh-fear) is a fermented dairy drink.

In recent years, many interesting, cultured dairy foods have experienced a surge in popularity, and kefir is probably the leader among these.

Making the drink requires two simple ingredients;

  • Whole milk
  • Kefir grains (a starter for fermentation)

Firstly, kefir grains are not one ingredient, and they contain various strains of bacteria, milk proteins, and yeast, which we will come to later.

After mixing the kefir grains with milk and allowing some time for the fermentation process to do its work, the kefir will be ready.


Kefir has a thick texture, and it shares some resemblances to yogurt in its taste profile. It is a sour and creamy drink.

Key Point: Kefir is a popular cultured dairy drink with a sour and creamy taste, and it contains a range of beneficial bacteria.

Kefir Health Benefits

While there are many claims about the benefits kefir can have on our health, not all of them are evidence-based.

Here we look at some of the research-backed benefits (and potential benefits) that kefir may have.

1) Kefir May Strengthen Bone and Improve Skeletal Health

Diagram Showing Bone Health and the Four Stages of Osteoporosis.

Kefir contains several compounds that help to strengthen bone and reduce the risk of bone density loss.

Bone loss is otherwise known as osteoporosis, and it is a disease that can cause bones to become increasingly weak and brittle. Unfortunately, this can increase the risk of falls and fractures in the elderly.

Over the long-term, osteoporosis can be debilitating, and it affects an estimated 200 million people worldwide, including more than 50 million American adults (1, 2).

On the positive side, kefir is an excellent source of calcium and vitamin K2, which both promote skeletal health (3, 4).

Calcium and Vitamin K2’s Role In Bone Health

One of the major functions of calcium is strengthening bone tissue, and it plays a vital role in bone remodeling and formation (5).

In combination with calcium, vitamin K2 has a synergistic effect, and it helps to ensure the bone gets sufficient vitamin K2.

Vitamin K2 does this by activating osteocalcin, a type of protein hormone that takes circulating calcium and binds it to the bone (6).

In a recent randomized controlled trial of osteoporotic patients, six months of daily kefir supplementation led to positive changes in bone mass density (7).

Key Point: Due to the compounds it contains, kefir likely has a protective effect on bone mass density.

2) Kefir Is Nutrient-Dense and Contains Numerous Essential Nutrients

The nutrient-density (nutrients per calorie) of food is a particularly useful way to judge the healthfulness of a given food.

In this case, kefir offers an excellent source of nutrients—particularly minerals—for relatively few calories.

For instance, here are some of the nutrients that just one cup (240 ml) of plain kefir provides (8);

  • Protein: 12 grams
  • Calcium: 40% RDI
  • Phosphorus: 43% RDI
  • Potassium: 16.5% RDI
  • Vitamin A: 10% RDI
  • Vitamin D: 17% RDI

Among these nutrients, protein, vitamin D and phosphorus also assist with the previously discussed bone health improvements (9).

One cup of kefir contains approximately 160 calories.

Key Point: Kefir is a good source of nutrients, and contains a range of essential vitamins and minerals.

3) Kefir Is Lower In Lactose Than Regular Milk

Infographic Showing the Signs and Symptoms of Lactose Intolerance.

During the fermentation process necessary for making kefir, the kefir grains slowly feed on the sugars in milk.

As this process takes place, the bacteria convert milk sugar (lactose) into lactic acid.

As a result, kefir contains much lower amounts of lactose than standard milk.

For example; Lifeways, one of the leading commercial kefir brands, claims that their kefir is “99% free of lactose”.

Furthermore, a randomized trial shows that in adults with lactose maldigestion, consuming kefir alongside regular milk improved lactose digestion and tolerance (10).

Compared to regular milk, kefir is likely an excellent option for people with lactose intolerance.

Key Point: The fermentation process of kefir results in a very low-lactose dairy drink. Also, it may lessen symptoms of lactose sensitivity when consumed alongside regular dairy.

4) Kefir Is a Rich Source of Probiotic Bacteria

Firstly, kefir is a source of numerous strains of probiotic bacteria, and these may include the following (11);

Lactobacillus acidophillus Lactobacillus brevis
Lactobacillus delbreuckii Lactobacillus fermentum
Lactobacillus kefirgranum Lactobacillus kefiranofaciens
Lactobacillus kefiri Lactobacillus parakenfiri
Lactococcus lactis cremoris Lactococcus lactic biovar diacetylactis
Leunostoc mesenteroids cremoris Leuconostoc mesenteroids ssp. mesenteroids
Streptococcus thermophilus

Research shows that these bacterial strains can survive digestion and colonize the gut, thereby promoting the microbiota and, potentially, health (12, 13).

The state of research on the microbiome/gut flora is in its relative infancy, and more research is necessary to gain a full understanding.

However, accumulating research suggests that the gut microbiome may play an important role in immune response and protection against disease (14, 15).

These probiotics may have a beneficial effect on blood sugar control too.

In a randomized controlled trial, type 2 diabetes patients consuming kefir had decreased fasting blood glucose and HBA1c levels compared to conventional fermented milk (16).

This larger variation in bacteria strains is one of the key differences between kefir and yogurt.

As a fermented product, it offers similar benefits as buttermilk in this regard.

Key Point: The probiotics in kefir have numerous beneficial (and potentially beneficial) effects on the body.

5) Kefir May Reduce the Severity of Allergies

Infographic Showing the Symptoms and Triggers of Common Allergies.

Some initial research suggests that the probiotic strains in kefir may help to lower allergic responses.

In an animal study, kefir “displayed anti-inflammatory and anti-allergic effects in a mouse asthma model” (17).

Mice studies do not infer that the same effect would be true in humans. However, it is an area for future research in human trials.

Additionally, kefir may hold a benefit for the treatment of the nasal condition allergic rhinitis.

On this note, numerous randomized controlled trials have shown that treatment with Lactobacillus probiotics, as found in kefir, reduces symptoms of allergic rhinitis in both adults and children (18).

Key Point: Further evidence is necessary to confirm this, but kefir may help to reduce the severity of certain allergies.

6) Kefir May Have Digestive Benefits

One of the most common claims around kefir is that it can have substantial benefits for digestive health.

For instance, numerous randomized trials suggest that probiotic milk drinks can aid (and maintain) the remission of ulcerative colitis (19).

Furthermore, a systematic review and meta-analysis of clinical trials found that probiotics help to alleviate the symptoms of irritable bowel syndrome (IBS) (20).

Explicitly focusing on kefir, a trial had 20 constipation patients drink 500 ml of kefir daily for four weeks. The results showed that kefir relieved constipation symptoms as well as overall “bowel satisfaction” scores (21).

Research on probiotics as a treatment option for digestive diseases is still very basic, and a wealth of studies are underway in this area.

From existing research, it is possible that probiotic foods like kefir hold promise for conditions ranging from allergies and stomach complaints to irritable bowel syndrome and other inflammatory disorders (22, 23).

Key Point: Kefir can potentially ease the symptoms of various digestive conditions.

7) Contains Immune-Enhancing Compounds

Illustration of a Man Blocking Viruses (Immune System Theme).

Some of the probiotic strains in kefir are associated with immune boosting properties.

One interesting study looked at participants who consumed 200 ml of kefir every day for six weeks. The results showed an increased immune response and lower circulating levels of several inflammatory markers (24).

Animal studies in this area also suggest that kefir can have an anti-inflammatory effect. In particular, the use of kefir appears to lower markers of inflammation in the presence of inflammatory gut conditions (25).

Further studies show that kefir may help to improve endothelial function as well as having an anti-bacterial effect against food pathogens (26, 27).

Key Point: Research shows that kefir has potential immune-boosting and anti-inflammatory properties.

8) Potential Weight Loss Benefits (Context Required)

Attributing weight loss benefits to a specific food is difficult. However, it is easy to find claims that kefir can lead to weight loss.

Overall, we should view this claim with skepticism as there is no real evidence to support it.

There are few recent studies on kefir and weight loss;

  • The first study shows that kefir supplementation can decrease weight gain in a high-fat mouse diet model. Again: humans are not mice, and nor does this finding prove weight loss (28).
  • Secondly, a randomized trial found that kefir use—in a non-energy-restricted diet—caused weight loss in dieters. However, a different control group using milk had virtually the same degree of weight loss in the study. The weight loss effect was likely due to the overall diet design rather than because it contained kefir or milk (29).

On the other hand, kefir does provide a decent nutrient profile, and it is rich in satiating protein.

These facts could make it a “smarter swap” for unhealthier snacks like candy or chips, which could have an indirect effect on weight loss.

Key Point: Kefir likely doesn’t have any unique weight loss-promoting effects. However, it could have an indirect effect on weight loss through its satiating properties.

9) Some Studies Suggest Kefir May Have Anticancer Properties

Woman Wearing Pink Ribbon Representing Fighting Against Cancer.

Some research claims that kefir may have anti-cancer properties.

First of all, some researchers believe that kefir’s bioactive compounds are responsible for these effects, namely polysaccharides—a type of carbohydrate—and peptides (30).

There is also the theory that fermented dairy products can suppress tumors by activating the immune system and by delaying enzymatic reactions that convert potential carcinogens to carcinogens (31).

A cell culture (test tube) study supports these claims, with kefir demonstrating that it can induce apoptosis (cell death) and slow the spread of cancer cells (32).

Also, a recent systematic review of 11 in-vitro (test tube) and experimental studies found that kefir had a consistent beneficial effect on cancer prevention (33).

However, care should be taken with the interpretation of these study results, as they are very weak evidence. Put simply; cell culture studies are very different from human clinical trials.

Until better evidence is available, we should take the “cancer-protective” effects of kefir with a large pinch of salt.

Key Point: Cell culture and experimental studies demonstrate that kefir can have anti-cancer effects. However, there is no evidence that this applies to the human body.

Side Effects

Although kefir has a collection of positive health effects, that does not mean it is healthy for everyone.

There are several common side effects that some people experience when they consume the drink.

Here are some potential drawbacks of using kefir.

1) Gastrointestinal Issues

It is not unusual for people consuming kefir to experience several digestive complaints.

This occurrence is more common when first starting to use kefir, but it can be a longer-term issue for some people.

These digestive complaints can include intestinal issues such as bloating, cramping, and gas pains.

Notably, these issues may not be exclusive to kefir, and they appear to be from consuming high amounts of probiotic bacteria in general. However, kefir is generally well tolerated after the first week or so of use. (34, 35).

Key Point: Gastrointestinal disturbances are not uncommon when first starting to use kefir.

2) Lactose Intolerance and Milk Allergy

Although kefir contains only trace amounts of lactose, it is not impossible that it could cause an issue for people with severe lactose intolerance.

Additionally, people with a genuine milk protein allergy will not tolerate kefir well; it still contains dairy proteins, and thus the responsible allergens.

Key Point: While people with lactose intolerance or lactose sensitivity may tolerate kefir, those with a genuine milk allergy should avoid it.

3) Some Store-Bought Kefir Products Are Full of Added Sugar

If you are buying a commercial brand of kefir, then make sure you read the label.

While some products are 100% pure kefir, others may contain numerous additional ingredients, including added sugar.

Flavored kefir products are particularly notable for this, and fruit-flavored kefir is often very high in sugar.

Key Point: Many branded kefir drinks contain large amounts of sugar and other additives.

Nutrition Facts

For reference purposes, here is the nutrition profile for kefir per 100 ml (8).

Calories and Macronutrients

Calorie/Macronutrient Amount (kcal/grams)
Calories 58 kcal
Carbohydrate 7.1 g
Fat 1.0 g
Protein 5.0 g

Major Vitamins

Mineral % RDI
Vitamin B12 50 %
Vitamin B2 39 %
Vitamin D 17 %
Vitamin A 10 %
Vitamin C 6 %

Major Minerals

Vitamin % RDI
Phosphorus 43 %
Calcium 40 %
Potassium 16.5 %
Sodium 7.4 %
Vitamin C 6 %
Key Point: Kefir is an excellent source of phosphorus, calcium, and vitamin D. It is also reasonably high in dietary protein.

How To Make Kefir At Home

Should you wish to avoid store-bought kefir and make your own, then this is something which is surprisingly easy to do.

All you need are the following ingredients/equipment;

  • Whole milk (cow and goat milk are both suitable)
  • Kefir grains: you can find these in local health stores, or you can buy them online.
  • A large glass jar/container


Note: depending on the size of your jar and how much kefir you wish to produce, you may want to use more or fewer ingredients.

In this case, per teaspoon of kefir grains, you will need approximately one and a half cups of milk.

  • Add 6 cups (1440 ml) of milk to the glass jar.
  • Add 4 tsp of kefir grains, and then stir the grains for a few seconds.
  • Make sure some space is left at the top of the jar and then put the lid back on the jar. During fermentation, gas will put pressure on the cover if there is no space.
  • Leave the glass jar at room temperature and allow 1-2 full days for the kefir to ferment.
  • Once the kefir is ready, it will have a clumpy look somewhat like cottage cheese or rice pudding. At this stage, strain the liquid into a container for drinking and then refrigerate it.
  • It is then possible to re-use the solids (kefir grains); add them back into the glass jar, re-fill with milk, and start the fermentation process over again.
  • You can drink the kefir plain or mix it with some berries for fruity-flavored kefir.
Key Point: It is quick and easy to make your own homemade kefir.

Final Thoughts

Kefir is a healthy drink that is relatively simple to make, tastes great, and has some interesting potential health benefits.

Overall, kefir is a cheap and nutritious choice that may help to improve our health.

For more on fermented dairy products, find out about the nutrient-dense quark or see this in-depth guide to sour cream.

Photo of author

Michael Joseph, MSc

Michael works as a nutrition educator in a community setting and holds a Master's Degree in Clinical Nutrition. He believes in providing reliable and objective nutritional information to allow informed decisions.

8 thoughts on “Kefir 101: Nutrition Facts, Health Benefits, and Side Effects”

  1. Is there an advantage to drinking kefir over eating homemade yogurt? Here kefir is very expensive and comes in large containers. I always throw half of it away. The grains aren’t readily available.

    • Kefir does contain more bacterial strains, so technically it may offer further benefits. That said, yogurt is a healthy choice too. If kefir is expensive and you’re wasting half of it, I’d just go with regular yogurt.

  2. My grandson loves Kéfir popsicles (I mix it with fruit and a little sugar).
    Does kefir keep its benefits when frozen?

  3. Hi Michael,
    thanks for the article, there’s some great information in it.

    I have been consuming milk Kefir for 6 months+ now and love it.
    Would you know the macro details for Kefir Whey V’s Kefir Curd? (using full fat milk)

    After a second ferment i strain the whey from the curd and consume them separately.
    I strain the curd to a slightly thick yogurt consistency (not quite a greek yogurt consistency).

    Thanks Regards

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