Brewer's Yeast
Also known as: saccharomyces cerevisiae
A byproduct of beer-making, added to pet food for B vitamins and flavour — and blamed (unfairly) for flea infestations.
What it actually is
Dried, deactivated Saccharomyces cerevisiae yeast, a byproduct of beer brewing. Rich in B-complex vitamins, protein, and minerals.
Why it's used in dog food
Cheap flavour enhancer that dogs love, plus a natural source of B vitamins and amino acids. Often added to make less palatable kibble more appealing.
A bit of history
Used as an animal feed supplement since the early 1900s. Popularized in dogs by the 'brewer's yeast repels fleas' folk wisdom of the 1970s — a claim that has never held up in controlled studies.
Pros
- •Natural source of B vitamins and trace minerals
- •Adds flavour without artificial ingredients
- •Contains beta-glucans, which may support immune function
Cons
- •Common allergen — some dogs react with itchy skin or ear infections
- •The flea-repelling claim is not supported by research
- •Can worsen yeast overgrowth in dogs already prone to it
Safety notes
Safe for most dogs. Skip it if your dog has recurring yeast infections or ear issues.
Sourcing & quality
Deactivated brewer's yeast (the pet-food form) is not live yeast and won't colonize the gut.
Commonly found in
Skip this if…
Your dog has recurring yeast infections or a known yeast sensitivity.
The verdict
Fine in moderation. The flea claim is folk wisdom, not science.