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Brewer’s Yeast is not good for Dogs and Cats

Brewer’s Yeast is not good for dogs and catsFind out why I don’t recommend Brewer’s yeast for dogs and cats, and discover safe, health supportive alternatives.

The Pet Food Industry and Pet Supplement Industry wants you to believe brewer’s yeast is good for your dog and cat.

The industry promotes brewer’s yeast as a highly desirable, editable substance that helps repel fleas, aids appetite, supports fur and skin health. All good right?



The pet industry fails to divulge the rest of the story – the FACT that…

Brewer’s yeast can trigger and contribute to short-term, and long-term health issues and conditions.

The FACT that Brewer’s yeast is NOT good for dogs and cats.

So why would the pet industry ardently promote the use of brewer’s yeast? Maintenance of high profit margins. Brewer’s yeast is a very low-cost, readily available substance.

What Is Brewer’s Yeast?

Brewer’s yeast is a type of one-celled fungus – scientific name “Saccharomyces cerevisiae”. The word Saccharomyces comes from the Greek word for sugar; and the fungus species name ‘cerevisiae’ comes from the Latin language, and means beer.

Saccharomyces cerevisiae was discovered thousands of years ago – perhaps during the making of bread. The Mesopotamians used a combination of sugar and water, fermented with the yeast to make an alcoholic beverage that later become known as beer.

Moving forward to Present Day, there are three main sources of Saccharomyces cerevisiae (Brewer’s yeast).

One – brewer’s yeast is still used by breweries to make beer.  Breweries cultivate the yeast on hops, malted barley or other grains. As the yeast sits in the grain-liquid solution to ferment, the yeast becomes contaminated. After the yeast has been used to ferment multiple times, the yeast microbes lose their viability, and are no longer useful to ferment beer. The inactive batch of yeast (now waste-yeast) must be replaced with new yeast.

Two – brewer’s yeast is also grown on molasses made from sugar beets or sugar cane specifically for the human and non-human-animal food and supplement manufacturing industry.

Three – Saccharomyces cerevisiae occurs naturally in the environment and is present in the gastrointestinal tract, on the skin of humans, and non-human animals including cats and dogs.

Brewer’s Yeast Use in Food and Supplements

Rather than discard the inactive waste-yeast breweries sell the inactive yeast to the food processing industry to be used as a food and supplement ingredient for humans, and non-human animals – farm animals, zoo animals, and domestic animals.

Brewer’s yeast is used in a wide range of made-for-pet products, including products marketed to you as ‘high’ quality, ‘all natural, ‘holistic’ and Veterinarian Prescription pet ‘food’, ‘treats’ and supplements.

But the truth is, Brewer’s yeast is not good for dogs or cats – period.

Beneficial Properties of (inactive) Brewer’s Yeast

Protein (non-mammalian protein)

Vitamin B


Harmful Properties of (inactive) Brewer’s Yeast

Degraded, Toxic Source of Minerals, Protein, and Vitamin B

Most brewer’s yeast is cultivated on conventional grains. Glyphosate is sprayed on conventional grain to desiccate (dry-out) the crops prior to harvesting, it is also used on GMO grains, GMO sugar beets, and GMO sugar cane.  All of these crops are known to contain high levels of glyphosate residue. On March 20, 2015 the International Agency for Research on Cancer (IARC) released its findings on glyphosate. IARC’s conclusion – there is “sufficient evidence of carcinogenicity”.

Non-organic and conventional crops are raised with synthetic chemical fertilizers that contain (toxic) heavy metals. The heavy metals are drawn into the plants via the root system and remain in the plant after harvesting.  Glyphosate, heavy metals an other toxins used in growing grain crops result in a crop that is deficient in nutritive value, and toxin-contaminated. The vitamins and minerals yielded from these crops are of poor quality – when Brewers’ Yeast is cultivated on these crops the nutritional value of the brewer’s yeast is also degraded, and contaminated with toxic residue.

Brewer’s Yeast – A source of MSG

The protein in Brewer’s yeast is a source of free glutamic acid – also known as MSG.

Glutamic acid (MSG) has an inflammatory effect on the brain that contributes to the onset of cognitive issues such as dementia. MSG is known as the ‘silent killer’.

Brewer’s Yeast Contributes to Overgrowth of Bad Bacteria

If your dog or cat is prone to, or is currently experiencing an overgrowth of bad bacteria, Brewer’s yeast can worsen the overgrowth.

The truth the pet food and supplement industry does NOT want you to know – Brewer’s yeast IS an inflammation-promoting substance.

Brewer’s Yeast Proven to Be Ineffective as a Flea Repellent

Inactive Brewer’s yeast (this is the type of Brewer’s yeast used by the food industry), has been proven ineffective as a flea repellent for dogs and cats.  Brewer’s yeast is not good for dogs and cats, and it IS proven to be ineffective as a repellent aid.

You Will Hear

You will hear people say, “since I put my dog on Brewer’s yeast his skin and fur is so much better” or “my dog isn’t getting so many fleas since I put her on brewer’s yeast”.

A dog may experience an improvement in one set of symptoms, but the dog or cat is also exposed to an increased toxic load, increased risk of inflammatory issues and conditions in the short and long-term.

While the Pet Industry profits, your cat and dog pay the ultimate price – degradation of his/her long-term health. A very unfair and unnecessary outcome when there are so many safe, affordable, alternatives.

Alternatives to Brewer’s Yeast

Supplemental Foods That Help Repel Insects and Parasites

There are many supplemental foods that can help your dog and cat be less-attractive to fleas.  These alternatives are inexpensive, readily available, and don’t have the adverse side effects that come with ingesting brewer’s yeast.

For examples of supplemental foods and herbs that support health and help make your dog and cat less attractive to insects and parasites, and instructions on dosing and use go here.

Species Appropriate Foods for Cats, Dogs – Rich in B Vitamins and Protein

A few examples below.  You can go to the link for each item to read more, including how to include the item in your dogs and cats diet…



Dark leafy greens






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Article and graphics by – Karen Rosenfeld, Ottawa Valley Dog Whisperer, Holistic Dog Behaviorist, Holistic Dog and Cat Wellness Specialist

About Karen

Dogs are my life, my work, my passion… I am a Dog Whisperer, Dog Behaviorist and Holistic Canine Wellness Adviser with a wealth of real-time, real-life experience living and working with dogs. For two and a half decades I have worked with and shared my life with dogs. My own dog pack is comprised of eleven dogs, various breeds and ages. I provide a full range of services including Obedience Training for puppies and dogs; canine Behavior Modification; canine Psychological Rehabilitation, specializing in assisting dogs that are experiencing extreme states of insecurity, anxiety and aggressive-reactive behavior; Diet, Nutrition and Wellness Advice and Plans for canines and felines…natural wisdom for you and your companion animal.

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