The Case for Buying Kefir Over Yogurt

While kefir may have started as a potential accident centuries ago, scientists studying the increasingly popular fermented milk drink believe it may just live up to the hype (even if its origin stories likely do not).

A review of more than two dozen human clinical trials published in March 2026 in the journal Healthcare concludes that consuming this probiotic-rich beverage offers small but meaningful improvements to the gut, the cardiovascular system, and even the mouth lining (which, like the intestines, is home to numerous good and bad bacteria). Kefir, the review states, is “a functional fermented milk beverage that can support human health on multiple levels.”

Adding to the evidence are the test tube and animal studies documenting expanded microbe colonies in the gastrointestinal tract post consumption, along with other benefits such as improved cholesterol, immunity, and blood glucose regulation, a different review reported in February 2026.

(Probiotics, Prebiotics, Postbiotics. What’s the Difference?)

“Kefir is a really wonderful drink from a health perspective,” says Jenna Smith, a registered dietitian and nutrition educator at the University of Illinois Extension.

The expanding health evidence may be partially why global sales have risen to an estimated $1.4 billion this year and are projected to top $1.7 billion in 2030, according to the firm Grand View Research. Dollar sales in the U.S. grew a hefty 28 percent in 2025, to $253 million, the Chicago-based research firm Circana calculates.

Still, kefir doesn’t cure diseases, as some online influences claim. And both reviews above note that additional high-quality studies are needed to fully understand the beverage’s health potential and limitations.

Kefir is said to have originated centuries ago in the Caucasus Mountains, located near modern-day Turkey, Georgia, and Russia. Some stories claim it was created by accident, after milk carried by shepherds inside animal-skin pouches reacted to the heat of the summer and the animal skins’ natural enzymes, leading to unintentional fermentation. In addition to producing the tangy beverage, clumps of so-called kefir “grains” then seeded future batches.

Other tales add to the intrigue, with the Raw Milk Institute reporting that a female Russian spy was sent to Caucasus’ Indigenous tribes at the turn of the 20th century to obtain the closely held grains. When a tribal prince fell in love with the woman, the grains were shared and soon became a staple in Russia.

Whatever its origins or spread, modern kefir is increasing in popularity because it contains a wide array of live bacteria and yeast—some 50 species per glass, compared to five or so in most yogurts. The documented strains, including numerous Lactobacillus, Bifidobacterium, and Acetobacter varieties, have been found to at least temporarily colonize in the intestinal tract.

“Normally, the more diverse the microbiome is, the healthier,” says Lioudmila Karnatovskaia, a critical care doctor at Mayo Clinic.

The wide microbial array in kefir is similar to that of kombucha, another popular fermented beverage, and is significantly higher than the fermented foods kimchi and sauerkraut. As a milk-based beverage, kefir is also high in calcium, vitamin D, and protein, Smith says.

(Kombucha and nootropics are all the rage. Do these drinks really work?)

Still, the bacteria taking up residence in someone’s gut depends both on an individual’s health and the product. When researchers at the University of Illinois sequenced the RNA of five commercially available kefirs, some of the species touted on the labels were missing. That could indicate purposeful mislabeling or, more likely, says Smith (who was not involved with her university’s research), an indication that live cultures can quickly degrade.

Several small clinical trials in the Healthcare review assessed kefir’s potential for specific health conditions, including in people with fatty liver disease, metabolic syndrome, and inflammatory bowel disease. A handful of disease markers improved, but others did not.

Karnatovskaia is intrigued by kefir’s potential for patients in her intensive care, who all receive high doses of antibiotics that alter the health of their gut. “In the first six hours of onset of critical illness, the microbiome diversity drops dramatically, and there’s an expansion of pathogenic strains,” she says.

In a preliminary study, she and colleagues gave 54 intensive-care patients from one quarter cup to one cup of kefir daily (delivered intravenously to those too sick to drink), then analyzed some of their stool samples. Several kefir-specific bacterial species were found, indicating some colonization in the gut.

“Making sure your gut recovers [from an ICU stay] as well as your entire body, that's important for a holistic recovery,” says Jaeyun Sung, a Mayo data scientist who worked on the study. The researchers also documented improvements in overall gut health in the patients using a Gut Microbiome Wellness Index that Sung and other researchers at Mayo Clinic created. The pair are seeking funding for a larger study with longer-term follow up.

Kefir was once a niche health food-store drink, but it is now available in many supermarkets, near the yogurt section. It can be bought in the original, tart flavor or in flavored varieties. “The bacterial strains are the same for either one,” Karnatovskaia says, although it’s important to be mindful of consuming too much sugar from flavored varieties.

People can also make their own kefir by purchasing traditional kefir grains from companies online and combining them with milk, then letting it ferment at room temperature for roughly a day.  

Kefir’s bacterial quantity degrades over time, so Smith recommends drinking it within a few days of opening a bottle. Although there are no official consumption guidelines, she suggests drinking kefir or other fermented products once a week—and daily when recovering from an illness.

That’s especially important during fall and winter, when increased circulating viral and bacterial illnesses can tax the intestines, Smith says. “You need to build the gut microbiome back up,” she says. “I think kefir is a great way to be able to do that.”