• Protein: Supports tissue maintenance, muscle function, and the production of enzymes and other important substances.

• Calcium: Contributes to normal bone and tooth development and maintenance.

• Phosphorus: Works with calcium in bone structure and participates in energy metabolism.

• Vitamin B12: Supports normal red blood cell formation and nervous system function.

• Riboflavin: Helps the body convert food into usable energy.

• Potassium: Supports normal muscle function, nerve signaling, and fluid balance.

• Vitamin B2 and other B vitamins: Help support several metabolic processes.

• Fat: The amount depends on whether whole, reduced-fat, or skim milk is used.

Kefir may also contain fermentation-derived compounds and live microorganisms.

The amount of lactose remaining after fermentation varies. Kefir often contains less lactose than the milk from which it was made, but it should not automatically be considered completely lactose-free.

Does Whole Milk Make Better Kefir?

Whole milk generally produces a richer, creamier kefir with a fuller mouthfeel.

Its higher fat content can influence texture and flavor, making the finished drink feel more substantial.

Reduced-fat and skim milk can also be fermented successfully. They usually produce a thinner drink, although fermentation time and culture activity can influence the final consistency.

From a nutritional perspective, the best option depends on individual needs and preferences. Whole milk provides more fat and energy, while lower-fat versions provide less total fat.

The probiotic characteristics of kefir are not determined solely by the fat content of the milk. The microorganisms and fermentation conditions are important as well.

1. Kefir Supports a Healthy Gut Microbiome

One of the most widely discussed benefits of kefir is its relationship with the gut microbiome.

The gut microbiome refers to the community of microorganisms that live in the digestive tract. It includes bacteria, viruses, fungi, and other microscopic organisms, although bacteria are among the most extensively studied members.

These microorganisms interact with the food we eat and participate in several processes related to digestion, metabolism, and immune function.

A balanced and diverse gut microbial community is generally considered an important part of digestive health. However, there is no single ideal microbiome composition that applies to every individual.

How Does the Gut Microbiome Work?

The digestive tract contains microorganisms that help process components of food that human digestive enzymes cannot fully break down.

For example, some intestinal bacteria ferment dietary fiber and produce short-chain fatty acids, including acetate, propionate, and butyrate.

These compounds participate in several processes involving the intestinal environment and metabolism.

The gut microbiome also interacts with the intestinal barrier and the immune system. Certain microorganisms help maintain an environment that supports normal intestinal function.

The relationship is complex. Different microorganisms can have different effects depending on their species, strain, location, and surrounding environment.

How Kefir May Influence Gut Microorganisms

Kefir contains live microorganisms when it has not been heat-treated after fermentation.

When consumed, some of these microorganisms may survive passage through parts of the digestive system. Others may be affected by stomach acid, digestive enzymes, and bile.

Certain strains may temporarily interact with microorganisms already living in the digestive tract.

Research has investigated whether kefir consumption can influence microbial composition, microbial activity, and digestive markers.

Some studies suggest that fermented foods can affect the gut microbiome. However, the exact effects depend on the food, the microbial strains, the amount consumed, and the individual.

It is therefore more accurate to say that kefir may contribute beneficial microorganisms and fermentation products to the diet than to claim that it permanently replaces harmful bacteria or completely balances the gut.

Why Microbial Diversity Matters

A varied gut microbial community can provide different metabolic functions.

Some microorganisms are particularly effective at fermenting specific types of fiber. Others produce different metabolites or interact with the intestinal environment in different ways.

Eating a varied diet containing vegetables, fruits, legumes, whole grains, nuts, and fermented foods can help support a healthy digestive ecosystem.

Kefir may be one useful component of this dietary pattern.

It should not be considered a substitute for fiber-rich foods. Fermented foods and dietary fiber contribute to gut health in different ways and can complement one another.

2. Kefir Contains Probiotics That May Support Digestive Health

Probiotics are live microorganisms that, when consumed in adequate amounts, provide a health benefit to the host.

This definition is important because not every microorganism found in fermented food automatically qualifies as a proven probiotic.

The health effects of probiotics are generally strain-specific. A particular strain may have evidence supporting one benefit, while another strain of the same species may not produce the same result.

Kefir is interesting because it can contain a mixture of bacteria and yeasts.

Lactic Acid Bacteria in Kefir

Lactic acid bacteria are among the most important microorganisms involved in kefir fermentation.

They convert lactose into lactic acid and help create the drink's characteristic sour taste.

Depending on the culture, kefir may contain microorganisms from genera such as Lactobacillus, Lactococcus, Leuconostoc, and related groups.

Some traditional kefir cultures also contain bacteria that produce kefiran, a complex carbohydrate associated with the grain structure.

These organisms contribute to fermentation and may influence the properties of the finished drink.

Yeasts Also Play a Role

Unlike many conventional yogurt cultures, traditional kefir grains often contain yeasts alongside bacteria.

The yeasts participate in fermentation and can produce carbon dioxide and small amounts of ethanol.

Their interactions with bacteria help create the distinctive flavor and texture of kefir.

The presence of yeasts is one reason traditional kefir has a different microbial profile from many other fermented dairy products.

However, not all commercial kefir products contain identical microorganisms. Some are made with selected starter cultures, and the final microbial composition depends on manufacturing practices.

Kefir and Digestive Comfort

Some people find that kefir is easier to tolerate than ordinary milk.

One possible reason is that fermentation reduces the amount of lactose.

Another possibility is that microbial enzymes contribute to lactose breakdown during digestion.

These factors may make kefir a useful option for some people who experience digestive discomfort after drinking regular milk.

However, individual responses vary. Kefir can still contain residual lactose, and people with severe lactose intolerance may experience symptoms.

It is also important to remember that digestive discomfort can have many causes. Persistent bloating, pain, diarrhea, or other symptoms should not automatically be attributed to an imbalance in gut bacteria.

3. Kefir May Help People Digest Lactose More Easily

Lactose is the naturally occurring sugar found in milk.

To digest lactose efficiently, the small intestine needs an enzyme called lactase. This enzyme breaks lactose into two simpler sugars: glucose and galactose.

Some people produce insufficient lactase after childhood. This condition is commonly called lactose malabsorption.

When undigested lactose reaches the large intestine, bacteria ferment it. This can produce gas and draw water into the bowel, leading to symptoms such as bloating, abdominal discomfort, and diarrhea.

Why Fermentation Changes Lactose Content

During kefir production, bacteria use lactose as an energy source.

As fermentation progresses, some lactose is converted into lactic acid and other substances.

This means that kefir often contains less lactose than the original milk.