- Kefir is a probiotic-rich drink made from milk and kefir grains.
- Kefir has many benefits, including supporting gut health and strengthening bones. It can also help with weight loss.
- Kefir could pose risks to those with lactose-intolerance and immunocompromised.
- For more information, visit Insider’s Health Reference Library.
As interest in probiotics has surged during recent years, so has the popularity of kefir — a fermented dairy drink rich in gut-friendly bacteria that support digestion, immune function, and nutrient absorption while keeping harmful pathogens in check.
Kefir is known for its health benefits. It can promote bone health and help with blood sugar management.
Here are some facts about kefir and how it might impact your health.
What is Kefir?
Kefir can be described as a fermented drink that is made by adding kefir grains (or milk) to the milk and letting it ferment for approximately 24 hours.
During this time bacteria and yeasts in the kefir grains turn the sugars in milk into
lactic acid
, making it taste slightly sour, says Tayler Silfverduk, a registered dietitian with a private practice.
Thanks to its creamy yet thin consistency and uniquely tart taste, kefir is often compared to drinkable yogurt, says Silfverduk.
You can find kefir in plain form or in a variety flavors such as strawberry, blueberry, or costco at most grocery stores or health food shops like Whole Foods and Costco.
There are a few different types of kefir, including:
- Milk kefir, which is the most common type in stores, and the one discussed in this article. Although traditionally made from cow’s milk it can also be made using goat, sheep or soy milk.
- Water kefir, which is dairy kefir made with sweetened water, juice, or coconut water in place of milk.
- Kefir grains, which are the colonies of bacteria used for fermenting water or milk. They look similar to a SCOBY start for kombucha.
Thanks to its impressive nutritional profile, it’s no surprise kefir has many potential health benefits, such as:
1. Supports gut health
Kefir has more probiotics than yogurt, says Elle Wittneben, a registered dietitian with Greater Boston Urology — and it also boasts a diverse range of bacteria strains.
In fact, a small 2021 study found that people on a diet high in fermented foods for 17 weeks experienced a greater increase in overall bacteria diversity than those on a high-fiber diet. Those “good” bacteria may help improve digestion and mental health.
2. Builds and maintains strong bones
Full-fat kefir is an excellent source of calcium. Calcium plays a key role in strengthening and maintaining your bones, thereby warding off osteoporosis.
Many kefir products are also fortified with vitamin D, according to Wittneben, which also plays an important role in protecting your bones by helping you effectively absorb calcium.
A small 2015 study found that osteoporotic patients who drank kefir for six months experienced greater increases in bone mineral density — a key measure for overall bone health — than those who just took a calcium supplement.
3. May control blood sugar
While more research is needed on kefir’s role in managing blood sugar, so far results seem promising.
For example, a small 2015 study found that people with type 2 diabetes who drank kefir as opposed to conventional fermented milk had reduced fasting blood glucose and HbA1C levels — in other words, lower blood sugar.
However, it is important to remember that flavored kefir products can have added sugar which could negate these benefits. So if you have diabetes or another related condition, be sure to buy plain kefir without added sugar.
4. May help with weight loss
Thanks in part to a high amount of satiating protein, kefir may help with weight loss.
Some bacteria, like those in the Lactobacillus family, have been found to increase the amount of fat excreted in the stool of healthy Japanese subjects, meaning their bodies absorbed less fat.
A 2016 study found overweight and
obese
women on a dairy-rich, non-calorie restricted diet who consumed either two servings of kefir drinks daily or low-fat dairy products for eight weeks had far greater reductions in weight, body mass index, and waist circumference than those who did not drink the kefir. The benefit could also be attributed, however, to the generality of dairy products as there was no difference in the kefir and low fat dairy groups.
5. Has antibacterial properties
Multiple studies have demonstrated that kefir shows antimicrobial activity against some pathogens, but it’s important to note that these studies have not been conducted in humans.
Additionally, a 2014 study in animals found that one of the probiotic strains that’s unique to kefir, Lactobacillus kefiri, can impede the growth of certain harmful bacteria, including salmonella. Kefir also contains a type of carbohydrate known as kefiran that has been shown to have antimicrobial effects in animal studies.
Kefir has been linked to health problems.
Kefir can be consumed by most people. Dietitians recommend that you start with one cup daily when you introduce it to your diet. Otherwise, a dramatic increase in probiotics could cause gas, bloating, and other unpleasant digestive symptoms.
Even people with lactose intolerance may drink it since the fermentation process converts the lactose in milk into lactic acid, which is easier to digest for lactose intolerants, says Silfverduk. However, since kefir is still technically a dairy product, look for kefir that’s 99% lactose-free or made with non-dairy alternatives, to avoid symptoms such as bloating, gas, and stomach cramps.
While it’s been suggested that the live bacteria in products like kefir could make those who are immunocompromised more vulnerable to infection, chances are extremely rare.
Wittneben suggests that you consume no more than one cup of kefir per day if your immune system is compromised. However, Wittneben also recommends consulting your doctor before consuming kefir.
Insider’s takeaway
Kefir is a creamy, tart-tasting fermented beverage that offers many potential benefits — thanks primarily to the fact that it’s rich in diverse probiotics.
In addition to supporting gut and bone health, kefir may also help with blood sugar regulation and
weight loss
.
Kefir can be consumed in small amounts by most people. If you have a compromised immune system or lactose intolerance, your physician should be consulted before you try kefir.