Fermented Foods for Dogs: Kefir, Bone Broth, and the Gut Microbiome

Why the Gut Microbiome Is the Starting Point

A dog's gastrointestinal tract hosts trillions of microorganisms — bacteria, fungi, archaea, and viruses — collectively called the gut microbiome.

When that community is diverse and balanced, it supports digestion, immune regulation, skin barrier function, and even mood via the gut-brain axis.

When it's out of balance — a state called dysbiosis — you may start to notice Signs of Poor Gut Health in Dogs like intermittent loose stools, excessive gas, dull coat, or itchiness.

That combination is rare in a single food source.

The caveat is that concentration and consistency vary widely between batches and brands — which is why fermented foods work best as a complement to a structured supplement routine rather than as a standalone strategy.

What Counts as a Fermented Food for Dogs?

Fermentation is a metabolic process in which microorganisms — mainly bacteria and yeasts — break down sugars into acids, gases, or alcohol. For dogs, the safest and most studied fermented foods fall into a few categories:

• Plain kefir (dairy) — cow's milk or goat's milk kefir, no added flavors or sweeteners
• Coconut kefir — dairy-free option made from coconut water or coconut milk
• Raw fermented goat's milk — lower in lactose than cow's milk; widely used in raw-feeding communities
• Unseasoned fermented vegetables — small amounts of plain sauerkraut (no onion, no garlic, no added salt above trace amounts) or fermented carrot
• Bone broth with probiotic cultures — some commercial bone broths are specifically fermented or enriched with live cultures

Foods to avoid: kombucha (can contain alcohol and excess sugar), yogurts with xylitol or artificial sweeteners, pickles or fermented foods preserved with high-sodium brine, kimchi (typically contains garlic and onion, both toxic to dogs), and any fermented beverages with alcohol content above trace levels.

Kefir for Dogs: What the Evidence Says

Kefir is a fermented dairy drink produced by kefir grains — complex communities of lactic acid bacteria and yeasts.

It typically contains Lactobacillus, Lactococcus, and Leuconostoc species alongside beneficial yeasts like Saccharomyces cerevisiae.

The fermentation process also breaks down most of the lactose, making kefir far easier for lactose-sensitive dogs to digest than plain milk.

Kefir portion guidance

Start at the lower end for at least one week. If stools remain firm and your dog shows no digestive upset, you can move to the full portion. Introduce kefir every other day for the first two weeks if your dog has a sensitive stomach.

Dogs with a history of pancreatitis should use low-fat or coconut kefir and only with veterinary guidance, since full-fat dairy can stress the pancreas.

Bone Broth: Fermented vs.

Standard

Plain, unseasoned bone broth has become a staple in the raw and whole-food feeding world — and for good reason.

Slow-simmered bones release collagen, glycine, proline, and minerals like calcium, magnesium, and phosphorus in a highly bioavailable form.

Glycine in particular supports glutathione synthesis (the body's master antioxidant) and may help maintain gut lining integrity.

Standard bone broth is not fermented — it's heat-extracted.

Fermented bone broth goes one step further: after simmering, cultures of lactic acid bacteria are added and allowed to ferment the broth, lowering pH, increasing SCFA content, and adding live microorganisms.

The result is a product with both the structural benefits of collagen and the microbial benefits of fermentation.

What to look for in a commercial bone broth

• No onion, garlic, leeks, or chives (all toxic to dogs)
• No added thickeners like carrageenan or guar gum in large amounts
• If marketed as "fermented," look for a live culture count or a "contains active cultures" statement

Bone broth is best used as a food topper or as a hydration aid for picky eaters and recovering dogs.

It is not a meal replacement.

Fermented Vegetables: Small Amounts, Big Caveats

Sauerkraut — fermented cabbage — is one of the oldest fermented foods on record. The fermentation process enriches it with Lactobacillus plantarum and other beneficial bacteria, B vitamins, and vitamin C.

In small amounts, plain sauerkraut can add a modest dose of live cultures to a dog's meal.

The key word is plain. Commercial sauerkraut is usually brined with significant amounts of salt — which dogs do not need in excess.

Look for a raw, refrigerated, unpasteurized sauerkraut with one or two ingredients (cabbage, salt) and rinse it briefly before serving to reduce sodium.

Fermented carrots and fermented beets are gentler alternatives for dogs prone to gas from cabbage.

Both ferment well in a simple brine and provide a broader range of plant fibers (prebiotics) that feed beneficial gut bacteria alongside the probiotic cultures they carry.

How Fermented Foods Interact With the Microbiome

The mechanism is layered. Live cultures from fermented foods colonize the gut transiently — most do not become permanent residents, but their passage still matters.

As they travel through, they:

• Compete with pathogenic bacteria for adhesion sites on the gut wall
• Produce bacteriocins — small antimicrobial proteins — that can suppress harmful species
• Stimulate secretory IgA production, a key component of mucosal immunity
• Leave behind postbiotic metabolites (SCFAs, peptides, organic acids) that benefit the resident microbial community

This last point is why postbiotics are generating so much research interest right now.

Fermented foods produce postbiotics naturally during the fermentation process — which is part of why whole fermented foods have effects that can't be fully replicated by a heat-killed probiotic alone.

That said, fermented foods are an inconsistent delivery vehicle. Culture counts aren't standardized, and pasteurized commercial products may have no live cultures at all.

Fermented Foods vs.

Probiotic Supplements: Not an Either/Or

The whole-food and supplement approaches are complementary. Fermented foods supply broad nutritional diversity; a supplement like Plentum supplies specific, evidence-backed strains and postbiotic metabolites at a reliable dose every day.

Practical Tips for Getting Started

A few principles that make fermented food introduction smoother:

• One new food at a time. If you introduce kefir and sauerkraut simultaneously, you won't know which one caused a reaction if something goes wrong.
• Cold is better. Refrigerated, unpasteurized products retain the most live cultures. Heat destroys them.
• Consistency matters more than quantity. A teaspoon of kefir daily for a month does more than a tablespoon randomly.
• Watch stool quality. Slightly looser stools in the first few days are normal as the microbiome adjusts. Persistent diarrhea, vomiting, or lethargy — stop and talk to your vet.
• Puppies and senior dogs: go slower. Developing and aging immune systems can be more reactive. Half portions, more gradual introduction.
• Immunocompromised dogs: vet first. Dogs on immunosuppressive medications should only receive fermented foods under veterinary supervision, as live organisms carry a small risk in severely compromised animals.

Primary veterinary reference

Use this owner guide alongside the WSAVA Global Nutrition Guidelines and the advice of the veterinarian managing the individual animal.

Related reading

• Natural Probiotic Foods for Dogs: Kefir, Yogurt & Fermented Options
• What Bone Broth Actually Does for Dogs