Brewers Dried Yeast in dog and cat food

Is it OK for dogs and cats?

Dogs

Yes, at the amounts studied. Dogs digested a diet with 15% brewer's yeast adequately, and a 10-week study found no harmful effects in healthy dogs given a brewers dried yeast supplement. One 2025 case report describes a dog that was allergic to purified yeast beta-glucans.

Cats

No study of brewers yeast itself in cats is among these sources. In a 2023 study funded by the yeast's maker, cats preferred a dry food with 10% dried Saccharomyces cerevisiae yeast (not described as brewer's yeast). They digested it as well as a yeast-free food and had urine values in the normal range. No problem was reported.

How settled this is: No known concern at the amounts used in complete foods

What brewers dried yeast is

Brewers dried yeast is the yeast left over from brewing beer, dried for use as a feed ingredient. Brewing yeasts are Saccharomyces species, such as S. cerevisiae. Spent yeast is the second by-product of brewing, and it is mainly used in animal feed. The EU Catalogue of feed materials lists it under 'yeasts, inactivated' (brewers' yeast, inactivated). All microorganisms used for fermentation must be inactivated, so no live yeast remains in the feed material. Yeast from brewing picks up bitter hop resins, which processors can remove ('debittering').

Why it is in pet food

It is used as a protein source. A 2023 study describes dried yeast as a possible non-animal alternative to rendered protein meals. Yeast also contains B vitamins, antioxidants, mannan- and fructo-oligosaccharides, and beta-glucans. The beta-glucan part has been reported to influence immunity and to protect the gut in dogs, and researchers say this needs more study. In a company-funded study, dogs ate a food with 10% dried yeast as well as or better than a yeast-free food, and cats ate more than twice as much of it over two days.

What it does in the food

A 2021 review reports that spent brewer's yeast contains about 40% crude protein, 59% total carbohydrates (23% beta-glucans) and 1% fat. A 2023 study, citing earlier work, gives brewer's yeast protein as about 50% of dry matter. In a 2014 study, dogs digested brewer's yeast protein better than the two sugarcane yeasts tested, and the authors found yeast digestibility adequate for dogs. A diet with 15% brewer's yeast had about 86% crude protein digestibility, with no significant difference from the control diet. Yeast also supplies B vitamins.

Safety and limits

Dogs: In a 2014 university study, dogs fed a diet with 15% brewer's yeast digested it adequately, and adding yeast had no effect on nitrogen balance. In a 2025 industry-funded study of 20 sled dogs, 10 had brewers dried yeast added on top of their food for 10 weeks (about 0.2 g per kg body weight a day). The authors found no harmful effects in the healthy dogs. In a 2023 study, dogs fed a dry food with 10% dried yeast showed no difference in stool quality or digestibility compared with a yeast-free food. The authors work for the company that makes that yeast and funded the study. A 2025 case report described one obese dog that developed itching, hair loss and red skin while eating a diet with 0.1% purified beta-glucans from Saccharomyces cerevisiae. The signs cleared when the diet was stopped and came back when it was fed again. The diet contained purified beta-glucans, not whole yeast. A single case shows such a reaction can happen, but not how often. Cats: In the 2023 study, cats fed 10% dried yeast had no difference in stool quality or digestibility, and their urine pH and specific gravity stayed in the normal range. No study of brewers yeast itself in cats is among these sources. In the EU, brewers' yeast is a listed feed material, and it must be inactivated.

What depends on the amount and the recipe

Results with yeast differ by yeast source, preparation and dose. Beta-glucan content may vary with brewing conditions. Debittering removes bitter hop compounds. The amount matters: the diet studies used 10-15% yeast, while the sled-dog study added a small daily amount on top of the food. The individual animal matters too, because one dog reacted to purified yeast beta-glucans.

Not the same as

• Brewers rice — A rice ingredient, not a yeast, despite the similar name.
• Brewers dried grains — The cereal residue left after brewing (listed in the EU catalogue as brewers' grains), here in dried form. It is a grain by-product, not yeast.
• Live yeast — Brewers dried yeast used as an EU feed material must be inactivated, so it does not supply live yeast cells.
• Yeast extract — Made by breaking down yeast cells and releasing their contents, often to add a savoury flavour. The EU lists yeast products from broken or fractionated cells separately from whole inactivated yeast.

Sources

1. Commission Regulation (EU) 2022/1104 amending the Catalogue of feed materials (entries 12.1.5 'Yeasts, inactivated [brewers' yeast, inactivated]', 12.1.12 'Yeasts products' and 1.12.12 'Brewers' grains') — Publications Office of the European Union (Official Journal L 177), 2022. The EU feed-material entry for inactivated yeasts, including brewers' yeast, and the Saccharomyces species it covers. All microorganisms used for fermentation must be inactivated so that no viable microorganisms remain in the feed material. There are separate entries for yeast products obtained by cracking or fractionating yeast cells, and for brewers' grains (cereal co-products of brewing, also sold dried).
2. Avramia I, Amariei S. Spent Brewer's Yeast as a Source of Insoluble beta-Glucans. Int J Mol Sci 22(2):825 — MDPI (peer-reviewed review; full text read via Europe PMC PMC7829969), 2021. Spent yeast is the second by-product of brewing and is mainly used in animal feed. Saccharomyces strains such as S. cerevisiae are used in beer making. Its composition is about 40% crude protein, 59% total carbohydrates (23% beta-glucans) and 1% lipids. Bitterness comes from hop resins, which can be removed by debittering. Glucan content may vary with brewing growth conditions. Spent yeast is also used for yeast extracts made by autolysis, which add a meaty flavour to food.
3. Martins MS et al. Brewer's yeast and sugarcane yeast as protein sources for dogs. J Anim Physiol Anim Nutr 98(5):948-957 — Wiley (peer-reviewed; abstract read via PubMed record PMID 24304448), 2014. Dogs were fed test diets with 15% brewer's yeast. Protein digestibility was lower for both sugarcane yeasts than for brewer's yeast. Yeast inclusion had no effect on nitrogen balance, and yeasts showed adequate digestibility in dogs.
4. Davenport GM, Block SS, Adolphe JL. Effects of extruded pet foods containing dried yeast (Saccharomyces cerevisiae) on palatability, nutrient digestibility, and fecal quality in dogs and cats. Transl Anim Sci 7(1):txad107 — Oxford University Press / American Society of Animal Science (peer-reviewed; full text read via Europe PMC PMC10516452), 2023. Dogs and cats were fed foods with 10% of a commercial dried whole-cell S. cerevisiae yeast. Dogs found them as palatable or more so, and cats ate more than twice as much over 2 days. Stool quality and digestibility did not differ, and cats' urine pH and specific gravity were in the normal range. Dried yeast may be an alternative to rendered protein meals. Brewer's yeast is about 50.2% protein on a dry basis (citing Martins). A diet with 15% brewer's yeast had 86.2% crude protein digestibility, with no significant difference from the control (citing Martins 2014). The authors are employees of the yeast's maker, which funded the study.
5. Rummell LM et al. The effects of supplemental brewers yeast on postprandial amino acid concentrations in healthy adult sled dogs. J Anim Sci 103:skaf180 — Oxford University Press / American Society of Animal Science (peer-reviewed; full text read via Europe PMC), 2025. Yeast is commonly used in pet food and contains B vitamins, antioxidants, mannan- and fructo-oligosaccharides and beta-glucans, which have been reported to influence immunity and protect the canine gut. Further study is warranted. Results differ by yeast source, preparation and dose. Of 20 dogs, 10 received brewers dried yeast top-dressed at about 0.2 g per kg body weight a day for 10 weeks, with no detrimental effects in healthy dogs. The research was funded by the F.L. Emmert Company.
6. Marchi PH et al. Allergic Reaction to Beta-Glucans in an Obese Dog: A Case Report of Confirmed and Suspected Sources. J Anim Physiol Anim Nutr — Wiley (peer-reviewed case report; abstract read via PubMed record PMID 40078087), 2025. One dog developed itching, hair loss and redness on a diet with 0.1% purified beta-1,3/1,6-glucans from Saccharomyces cerevisiae. The signs resolved when the diet was withdrawn and came back on re-challenge.

Checked against these sources on 2026-10-15. Definitions are in our own words. This is a reading aid, not veterinary advice: a vet who knows your animal comes first.