Kefir: 15 Science-Backed Health Benefits of This Probiotic Drink

Kefir is a traditional fermented milk drink that has attracted growing attention for its potential health benefits, particularly its ability to support digestive health. Naturally rich in beneficial bacteria and yeasts, kefir offers a diverse combination of microorganisms that may help maintain a healthy balance of gut bacteria. Beyond digestion, research suggests that drinking kefir may support immune function, contribute to stronger bones, improve certain metabolic markers, and provide other benefits for overall well-being.

Traditionally, kefir is made by adding small clusters of living microorganisms, known as kefir grains, to cow's, goat's, or sheep's milk. The mixture is left to ferment, producing a slightly sour, refreshing drink with a consistency somewhere between milk and yogurt. Today, dairy-free alternatives made with water, coconut water, and plant-based beverages are also available.

What makes kefir particularly interesting is its microbial diversity. Unlike many conventional fermented dairy products, traditional kefir contains a combination of lactic acid bacteria, acetic acid bacteria, and yeasts. During fermentation, these microorganisms transform some of the milk's natural sugars and proteins, producing organic acids, peptides, and other compounds that contribute to kefir's distinctive flavor and nutritional characteristics.

These microorganisms may also interact with the complex community of bacteria living in the human digestive tract, commonly known as the gut microbiome. Because the gut microbiome is involved in digestion, immune regulation, and several metabolic processes, maintaining a healthy microbial environment is an important part of overall health.

Kefir is also a source of high-quality protein, calcium, phosphorus, potassium, and several B vitamins. Furthermore, fermentation reduces much of the lactose naturally present in milk, making kefir easier to digest for some people with lactose intolerance.

However, it is important to distinguish between promising research findings and benefits that have been firmly established in humans. Although laboratory and animal studies have identified numerous potentially beneficial properties of kefir, human clinical trials are still relatively limited. A systematic review published in Nutrition Reviews in 2023 examined 16 randomized controlled studies and concluded that more high-quality research is necessary before kefir can be recommended as a treatment for specific medical conditions.

In this comprehensive guide, we will explore what kefir is, how it is made, its nutritional value, and 15 potential health benefits supported by scientific research. We will also examine possible side effects, explain how kefir compares with yogurt and probiotic supplements, and provide practical instructions for preparing homemade kefir.

What Is Kefir?

Kefir is a fermented beverage traditionally produced by adding kefir grains to milk and allowing the mixture to ferment at room temperature for approximately 18 to 24 hours, although fermentation time varies depending on temperature, the quantity of grains, and the desired flavor.

The word "kefir" is commonly associated with the Turkish word keyif, meaning pleasure or a feeling of well-being. The drink has a long history in the Caucasus region and has traditionally been consumed in parts of Eastern Europe, Russia, and Central Asia.

Kefir is sometimes described as drinkable yogurt because the two products share a tangy flavor and contain beneficial microorganisms. However, kefir has a distinct fermentation process and a more diverse microbial composition.

During fermentation, microorganisms consume lactose, the natural sugar found in milk, and produce lactic acid, carbon dioxide, small amounts of alcohol, and other metabolic compounds. These changes give kefir its characteristic slightly sour flavor, mild effervescence, and creamy consistency.

Traditional milk kefir generally has a thinner texture than Greek yogurt but is thicker than ordinary milk. Its flavor can range from mildly tangy to distinctly sour depending on how long it has fermented.

If you find the taste too strong initially, you can blend kefir with fresh berries, bananas, mangoes, or other fruits. A small amount of honey can also be added, although people monitoring their blood sugar should account for the additional carbohydrates.

Milk Kefir, Water Kefir, and Kombucha: What Is the Difference?

Not all fermented drinks are made in the same way. Milk kefir, water kefir, and kombucha each contain different microbial communities and offer different nutritional characteristics.

Milk kefir

Milk kefir is the traditional form of kefir. It is made by fermenting cow's, goat's, or sheep's milk with milk kefir grains.

It provides protein, calcium, phosphorus, and other nutrients naturally present in milk. Depending on the fermentation process, it also contains a variety of live bacteria and yeasts.

Because it is made from dairy milk, milk kefir is not suitable for people with a milk protein allergy. Although fermentation reduces lactose, it does not necessarily eliminate all of it.

Water kefir

Water kefir is a dairy-free fermented drink made using water kefir grains. These translucent, gelatinous grains contain a community of bacteria and yeasts that ferment sugar dissolved in water or another suitable liquid.

Some people prepare water kefir using coconut water or diluted fruit juice. The resulting beverage is usually lightly sweet, refreshing, and mildly fizzy.

Water kefir can provide live microorganisms, but it does not naturally contain the same amount of protein, calcium, or other dairy-derived nutrients as milk kefir.

Its nutritional composition depends heavily on the ingredients used and the fermentation process.

Kombucha

Kombucha is another popular fermented beverage, but it is made from sweetened tea rather than milk.

It is produced using a symbiotic culture of bacteria and yeast, commonly called a SCOBY. During fermentation, microorganisms transform some of the sugar in the tea into organic acids and other compounds.

Kombucha generally has a sharper, more acidic flavor than kefir. It may also contain small amounts of caffeine and alcohol, depending on the tea and fermentation conditions.

According to research published in the journal Frontiers in Microbiology, fermented beverages can contain different microbial communities and fermentation products. Therefore, milk kefir, water kefir, and kombucha should not be considered nutritionally interchangeable.

What Are Milk Kefir Grains?

Milk kefir grains are the essential ingredient used to produce traditional kefir.

Despite their name, they are not cereal grains like wheat, rice, or oats. Instead, they are small, irregular clusters of microorganisms held together in a natural matrix of proteins and complex carbohydrates.

They usually resemble tiny cauliflower florets, with a white or cream-colored appearance and a soft, gelatinous texture.

Their size can vary from a few millimeters to several centimeters. When properly maintained, kefir grains grow and multiply during repeated fermentation cycles.

According to research published in Frontiers in Microbiology, kefir grains contain a complex community of microorganisms, including:

• Lactic acid bacteria, which convert lactose into lactic acid.

• Acetic acid bacteria, which contribute to the production of organic acids.

• Yeasts, which help produce carbon dioxide and other fermentation compounds.

• Various beneficial bacterial species, including members of the Lactobacillus, Lactococcus, and Leuconostoc groups.

One particularly interesting characteristic of kefir grains is the presence of a complex polysaccharide called kefiran. This substance contributes to the grains' structure and has attracted scientific interest because of its potential biological activities.