Raw kefir is a fermented milk drink made from unpasteurized milk that has been cultured with kefir grains, a living colony of bacteria and yeast. Unlike regular kefir sold in most grocery stores, the milk used in raw kefir has never been heated to kill microorganisms, which means it retains its native bacteria, enzymes, and proteins alongside the beneficial microbes introduced during fermentation. The result is a tart, slightly effervescent drink with a thinner consistency than yogurt and a noticeably more complex flavor.
How Raw Kefir Differs From Regular Kefir
All kefir starts the same way: kefir grains, which are rubbery, cauliflower-like clusters of bacteria and yeast bound together by a protein matrix, are added to milk and left to ferment at room temperature for roughly 24 hours. The microbes in the grains consume lactose, producing lactic acid, carbon dioxide, and small amounts of alcohol. What separates raw kefir from the pasteurized version is the milk itself.
Pasteurized milk has been heated to at least 161°F (72°C) to destroy harmful bacteria. That process also eliminates the milk’s own beneficial bacteria and deactivates natural enzymes. When kefir grains ferment pasteurized milk, the only microbes present are those from the grains. In raw milk, the native bacterial community is still alive, so fermentation involves both the grain organisms and the milk’s original flora working together. This typically produces a broader diversity of microbes in the finished product compared to kefir made from pasteurized milk, and broader even than homemade yogurt, which requires heating the milk as part of its preparation.
What’s in Raw Kefir: Probiotics and Peptides
Kefir in general is one of the most microbe-rich fermented foods available. A well-fermented batch can contain roughly 3 billion colony-forming units per milliliter, a concentration that dwarfs most commercial probiotic capsules. The microbial community includes multiple species of lactobacilli, along with yeasts that are rarely found in yogurt. These organisms don’t just pass through your gut. Many of them survive stomach acid and colonize the intestinal lining, where they compete with harmful bacteria for space and resources.
Raw kefir adds another layer. Because the milk hasn’t been heat-treated, naturally occurring enzymes called proteases (which break down proteins) remain active. During fermentation, these enzymes work alongside microbial enzymes to chop milk proteins, especially caseins, into smaller fragments called bioactive peptides. Research published in Food & Function found that the number of unique peptides and their total abundance increases by several orders of magnitude during fermentation. Heating the milk before fermentation significantly reduced the diversity of these peptides. Some of these protein fragments have demonstrated effects on immune signaling and blood pressure regulation in laboratory studies, though the practical health impact of consuming them in kefir is still being quantified.
Making Raw Kefir at Home
The process is simple. You place kefir grains in a glass jar, cover them with raw milk (a common ratio is one tablespoon of grains per cup of milk), loosely cover the jar, and leave it at room temperature for 12 to 24 hours. When the milk has thickened and smells tangy, you strain out the grains with a non-metal strainer and use them for the next batch. The strained liquid is your kefir.
One important detail: if you’re starting with dehydrated or newly purchased kefir grains, activate them first in pasteurized milk for several batches before switching to raw. Raw milk contains its own bacterial community, and those organisms can outcompete fragile, rehydrating grains before they’ve had a chance to establish themselves. Once the grains are producing consistent, well-fermented kefir in pasteurized milk, you can transition them to raw milk gradually, mixing increasing proportions of raw milk over a few batches until you’re using it exclusively.
Safety Considerations
The central concern with any raw dairy product is the potential presence of harmful bacteria. Salmonella, E. coli, Listeria, and Staphylococcus aureus have all been detected in raw milk. Fermentation does reduce these populations. Research on traditionally fermented raw milk products found that pathogens present in the starting milk survived fermentation but dropped to levels below standard microbiological safety thresholds after 48 to 72 hours. The lactic acid produced during fermentation lowers the pH, creating an environment that suppresses many harmful organisms.
That said, “suppressed” is not the same as “eliminated.” The safety of raw kefir depends heavily on the cleanliness of the milk source, the health of the animals, and how the milk was handled before fermentation. People with compromised immune systems, pregnant women, young children, and older adults face higher risk from any raw dairy product. For healthy adults sourcing milk from a trusted farm with good sanitation practices, the risk is lower but not zero.
Where You Can Get It
Federal law prohibits selling unpasteurized milk across state lines, but individual states set their own rules for sales within their borders. Some states allow raw milk to be sold in retail stores. Others permit sales only at the farm where the milk was produced. A handful of states ban the sale of raw milk to consumers entirely. Because raw kefir is made from raw milk, it falls under these same restrictions. You’re unlikely to find raw kefir in a conventional grocery store. Most people who drink it either make it at home from raw milk purchased locally or buy it from small farms and specialty producers who sell directly to consumers.
If you don’t have access to raw milk, fermenting store-bought pasteurized milk with kefir grains still produces a probiotic-rich drink with far more microbial diversity than commercial yogurt. You lose the native milk enzymes and some peptide complexity, but you keep the core benefits of kefir fermentation. For many people, that’s a practical and worthwhile middle ground.