Research & Insights

Brewer’s Yeast in Dog Food: Nutrition, Evidence and Formulation Notes

Published October 31, 2026

Chart of fecal butyrate in dogs fed a dried yeast diet (103.9 µmol/g) versus other diets (46.2 µmol/g), with protein digestibility and palatability results from dog studies

Brewer’s dried yeast has been part of dog food for decades, and the reasons are practical. It adds digestible protein, natural B-vitamins and a savoury taste that dogs readily accept, and it carries yeast cell wall fractions linked to gut health. Most dry and wet dog foods use it at 1–3% of the recipe, while controlled studies have fed whole yeast at 10–15% without harming digestibility or stool quality. This guide sets out what the ingredient contributes, what research in dogs shows, and the few cases where it should be limited.

What brewer’s dried yeast is

Brewer’s dried yeast is Saccharomyces cerevisiae recovered after beer fermentation, then inactivated and dried. Some suppliers also debitter it; that step is optional and depends on the application. The US feed definition describes it as dried, non-fermentative, non-extracted yeast from brewing with at least 35% crude protein. Because it is inactive, it cannot ferment or rise in kibble, treats or wet food. TBESBY dried brewer’s yeast is drum-dried to 40–46% crude protein with moisture below 10%.

The ingredient is often confused with active baking yeast, nutritional yeast and yeast extract. Each is a different product with a different label term; our guides on brewer’s vs nutritional yeast and brewer’s yeast vs yeast extract cover the differences.

What it adds to a dog food

Protein and amino acids

Across more than 100 analyses compiled by Feedipedia, dehydrated brewer’s yeast averages about 49% crude protein on a dry matter basis. Lysine makes up about 6.3% of that protein, which is high for a non-animal ingredient and useful in recipes built on cereals. Glutamic acid is the most abundant amino acid at about 15% of protein; together with the yeast’s nucleotides, it helps explain why dogs find yeast savoury.

B-vitamins

Yeast synthesises its own B-vitamins, so brewer’s yeast naturally carries thiamine, riboflavin, niacin, pyridoxine and folic acid. Commercial brewer’s yeast products for dogs guarantee these on their labels. In a complete dog food the premix still does the heavy lifting, but yeast adds a natural source that supports “naturally rich in” positioning.

Cell wall fractions

The cell wall makes up roughly 15–30% of the yeast’s dry weight and is built mostly from beta-glucans and mannoproteins, the same fractions sold in purified form as yeast cell wall. At 2% inclusion, brewer’s yeast therefore brings an estimated 0.3–0.6% of wall material into the food. Our guide on yeast cell wall vs brewer’s dried yeast explains when the whole cell is enough and when a dosed wall product is the better choice.

What the research shows in dogs

Digestibility. Martins and colleagues (2014) replaced 15% of a reference diet with brewer’s yeast or with one of two sugarcane yeasts and measured total tract digestibility. Brewer’s yeast delivered higher protein digestibility and metabolisable energy than both sugarcane yeasts; the underlying thesis reports apparent protein digestibility of about 96% for the brewer’s yeast. No effect on nitrogen balance or post-meal blood urea was found.

Palatability. Davenport and colleagues (2023) fed extruded foods with and without 10% dried whole-cell S. cerevisiae. Dogs chose the yeast food first significantly more often across two days (P = 0.005), and total intake was equal or higher. Nutrient digestibility and stool quality did not differ from the control food. The yeast tested was a dried yeast rather than brewer’s yeast specifically, but the cell is the same species.

Gut fermentation. Reilly and colleagues (2021) used a dried yeast as a main protein source in extruded beagle diets and compared it with legume diets and a poultry by-product meal control. All diets were more than 80% digestible and stool quality was rated ideal. The yeast diet produced the highest fecal butyrate of all treatments, 103.9 µmol/g against an average of 46.2 µmol/g for the others. Butyrate is the main energy source for colon cells, so the shift is a favourable one.

Microbiota and immunity. Yeast products have also been studied at low doses for gut support. Lin and colleagues (2019) fed a S. cerevisiae fermentation product at 125, 250 and 500 mg per day and saw higher fecal Bifidobacterium with lower phenol and indole concentrations. Middelbos and colleagues (2007) found that fecal E. coli declined as yeast cell wall supplementation rose from 0.05% to 0.65% of the diet. These studies used yeast-derived products rather than brewer’s yeast itself, so they indicate the direction of effect rather than a guaranteed result.

Where to be careful

Purines and urate-forming breeds. Yeast is rich in nucleic acids, which the body breaks down to purines and then uric acid. In most dogs the liver converts uric acid to allantoin, which is easily excreted. Breeds with an inherited defect in that conversion, such as Dalmatians, English bulldogs and Black Russian terriers, excrete more uric acid and are prone to urate stones. Their diets are managed with low-purine ingredients, and guidance for these dogs lists brewer’s yeast among the ingredients to avoid. Low-purine and urinary veterinary diets should leave yeast out; for maintenance foods aimed at the general dog population, this is not a reason to exclude it.

Claims. Keep claims to what the evidence supports: protein, palatability, B-vitamins and a contribution to gut health. Popular beliefs, such as brewer’s yeast repelling fleas or ticks, are not supported by controlled studies and do not belong on a pack.

Quality. As with any by-product ingredient, the result depends on processing. Ask for a fully inactivated product with a Certificate of Analysis covering protein, moisture and ash on every shipment, plus microbiological and mycotoxin limits that meet your market’s pet food rules.

How much to use

Most dry dog foods that use brewer’s dried yeast include it at about 1–3% of the recipe. Higher levels are used when yeast is also a protein source. The right level depends on the job the yeast is doing.

Use	Typical inclusion	Main purpose
Palatant and B-vitamin source	About 1–3% of the recipe	Acceptance, savoury note, natural B-vitamins
Declared functional ingredient	Around 2–3%, often stated on the label	Clean-label positioning
Higher-inclusion yeast formulas	Up to 5–7% yeast-based ingredients, as reported by one ingredient supplier	Protein contribution plus palatability
Research diets	10–15% of the diet	Testing digestibility and preference

Treats and toppers built around flavour can carry more; a short palatability test sets the level.

What changes as you raise the level?

Inclusion	What you gain	What to watch
1–3%	Palatability, B-vitamins, a recognisable label ingredient	Little effect on protein targets
3–7%	Meaningful protein contribution, stronger yeast note	Amino acid balance, methionine in particular; cost per point of protein
Above 7%	Larger replacement of other proteins	Taste acceptance in your base, kibble expansion and texture, limited published data

Neither published dog study is a long-term feeding trial at high inclusion. Confirm any level well above commercial practice with your own palatability and stool quality check before launch.

How much brewer’s yeast is in dog food?

Usually about 1–3% of a dry recipe. Some formulas use more, and research diets have tested 10–15%.

Does the yeast level need to be declared?

The ingredient must appear in the ingredient list. A percentage is usually only required when the yeast is highlighted in the product name or claims, under the rules of your market.

A short checklist for dog food makers

Specify inactive, non-extracted brewer’s dried yeast with a stated minimum crude protein, and state whether debittering is required for your formula.
Agree limits for moisture, ash, microbiology and mycotoxins, and a Certificate of Analysis with each shipment.
Choose the inclusion level by role: function, flavour or protein.
Exclude yeast from low-purine and urinary diets.
Keep pack claims within the evidence.

Free: Brewer’s Yeast Formulation Kit

Inclusion levels by species, the five spec numbers to check, a supplier checklist and storage notes in one 6-page PDF.

Download the kit · Request a sample