Ask the Vegan Vet: What's the Deal with Brewer's Yeast?

My dog was diagnosed with a brewer's yeast allergy through a food allergy blood test. I see that brewer's yeast is an ingredient in v-dog kibble. Should I steer clear of this food? - Anthony D.

Dear Anthony,

The brewer's yeast allergy question is a great one. I have an extensive veterinary dermatology background and I've never heard of this. When I looked online, I saw it on several lay person's dog websites, but nothing indicating this food allergy exists in the veterinary literature to my knowledge.

The only reference I could find in veterinary literature is to a study about food allergy blood tests. Apparently some veterinary allergy labs are doing food allergy blood tests, which may include Brewer's yeast in the panel. Unfortunately, the only way to diagnose a food allergy is with a dietary elimination trial. Food allergy blood tests are not considered accurate by veterinary dermatologists. These tests are so inaccurate that both water and pet fur sent in have "tested positive" for allergies to certain foods. The fact that Brewer's yeast is included on the blood panel may lead to false positives on tests that general practice vets may send out (veterinary dermatologists do not use food allergy blood tests).

If there is any confusion with other yeasts, Brewer's yeast doesn't cause the type of excessive gas production that yeast used in bread recipes does. Bread yeast found in raw dough can make dogs very sick if they eat too much of it.

According to Tuft's veterinary nutrition service, "The most commonly reported food allergies in dogs and cats are chicken, beef, dairy, and egg (and fish for cats). There is nothing particularly special about these ingredients other than they have been the most common ingredients in pet foods for the past few decades, so both cats and dogs often have been exposed to them a lot. What surprises many pet owners is that grains are actually uncommon causes of food allergies – most pets are allergic to animal proteins!"

"MYTH: Brewers yeast in the diet will cause a yeast infection in the skin.

FACT: Brewer’s yeast will NOT influence Malassezia [skin yeast] overgrowth.

Brewer’s yeast is Saccharomyces cerevisiae and is considered a source of vitamin B, selenium, and chromium. There is one 2006 study in the human literature that showed patients demonstrated an INCREASE in salivary gland IgA levels after oral administration. Although this study is not in animals and is quite limited, it would appear to contradict the myth. It is doubtful that Brewer’s yeast would be either beneficial OR harmful for yeast dermatitis patients."

I hope this information helps clear up some of the confusion about Brewer's yeast.

All the best,

Dr. Lorelei Wakefield, VMD

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