by Amanda Bradbery, Ph.D.

Brewer’s Yeast vs. Saccharomyces boulardii

Brewer’s Yeast vs. Saccharomyces boulardii

Saccharomyces cerevisiae, also known as Brewer’s Yeast, is definitely not the same as Saccharomyces boulardii

S. boulardii, the yeast-based probiotic that’s resistant against antibiotics and helps balance our animals’ digestive tracts, is a strain of S. cerevisiae, but it has many other properties that make it unique from S. cerevisiae, or the commonly supplemented Brewer’s Yeast. 

Let’s investigate how these probiotics affect our dogs, cats, and horses, and if there’s any benefit to adding either ingredient to their daily diet.

Where Do Brewer’s Yeast and S. boulardii Come From?

Saccharomyces cerevisiae (i.e. Brewer’s Yeast) is a versatile fungus that plays an important role in fermentation, including being a key factor in bread and beer-making. 

Brewer’s Yeast is a by-product of the fermentation processes of beer production, thus its name Brewer’s Yeast. Once the brewing process is complete, the yeast is separated from the beer and can then be harvested, dried, and collected into containers, typically deactivated

S. boulardii, on the other hand, is a strain of S. cerevisiae that was originally discovered in nature in 1923 on Mangosteen skins. It is genetically similar to S. cerevisiae but with unique probiotic qualities that contribute to its survival in the gastrointestinal tract. 

As such, S. boulardii is supplemented in its active form compared to the deactivated nature of Brewer’s Yeast which is incapable of surviving in the gastrointestinal tract. 

Dr. Amanda Bradbery, FullBucket Animal Nutritionist comments, “Because the S. boulardii in FullBucket products are living microorganisms, they elicit a very different, and often more potent, benefit to the animal than Brewer’s Yeast would, especially when the goal is to benefit gut health.” 

Active Dry Yeast vs. Deactivated Brewer’s Yeast

Active Dry Yeast and Brewer’s Yeast are both approved ingredients for use in animal feeds but provide different nutrients and benefits that are not always clear to the consumer. 

Both are considered probiotics, which suggests that they provide similar benefits when supplemented, but that is not typically the case. 

Active Dry Yeast is a live yeast organism of S. cerevisiae or the more specific strain of S. boulardii, as is used in FullBucket products. This particular ingredient provides the classically recognized probiotic benefits of increasing fermentative digestion, binding and detoxifying potential pathogens, and improving overall gastrointestinal health. 

Deactivated Brewer’s Yeast is a by-product of beer brewing, is not a living microorganism at the time of supplementation, and instead provides a potent source of B-vitamins and other proteins, It often has a more bitter flavor. 

Are Brewer’s Yeast and S. boulardii Safe for Dogs, Cats, and Horses? 

Both Brewer’s Yeast and S. boulardii are safe for dogs, cats, and horses, and are recognized by regulatory bodies as “GRAS, or Generally Regarded as Safe,” despite providing different benefits when supplemented. 

A common misconception is that consuming active yeast (S. cerevisiae or S. boulardii) as opposed to deactivated Brewer’s Yeast will have the same effects as brewing beer or making bread where the animal’s gut will ferment alcohol or make rising dough in the same way it is used in the brewing and baking industries. 

If this was true, this would, in fact, make the ingredient unsafe. However, this myth can be easily debunked.

A biochemist by the name of Dr. Joseph L. Owades knew that yeast produces an enzyme called Alcohol Dehydrogenase (ADH) that converts alcohol to acetaldehyde. 

Using this knowledge, he would consume 2 tbsp of active dry yeast before indulging in a little beer drinking in the hopes that the yeast would convert the alcohol to acetaldehyde and mitigate the impending drunkenness. He received a patent for this in 2005 prior to his passing. This same strategy was adopted by the CEO of Sam Adams parent company, Jim Koch. 

Unfortunately, this was later found to make the hangover worse so let’s get back to the animal benefits (don’t try this at home, kids)! 

The Benefits of S. boulardii and Brewer’s Yeast. Which is Superior for Gut Health? 

With the understanding that both ingredients are safe for our animals, it’s time to dive into the benefits of each. 

Brewer’s Yeast Benefits

Brewer’s Yeast, because it is often deactivated, is a good source of nutrition for your dog, cat, or horse but is not as potent of a probiotic as S. boulardii because in its deactivated form, it does not provide the traditional gut health benefits.

Brewer's Yeast has several benefits with the most discussed involving skin and coat health. Since it's full of B-vitamins and amino acids, it may improve skin health, promote a healthy coat, and reduce shedding. Aiding in the prevention of dermatitis is also an added benefit. 

Brewer's Yeast also contains chromium, which is key for managing blood sugar levels and can be helpful for animals with metabolic disorders like insulin resistance, Cushing's Disease, or diabetes. The antioxidants in this yeast type can also give the immune system a boost to protect against foreign invaders that cause illness.

S. Boulardii Benefits

Active Dry Yeast in the form of S. boulardii, provides more potent gut health benefits compared to Brewer’s Yeast. These benefits include pathogen binding, antimicrobial benefits against common pathogens, immune boosting effects, digestive aid, and intestinal lining integrity. 

Because S. boulardii is a specific strain of S. cerevisiae, its effects have proven more reliable and repeatable in many different environments or clinical uses. 

For example, S. boulardii is better able to survive the harsh environment of the gastrointestinal tract to elicit benefits compared to its S. cerevisiae counterpart. It is also resistant to antibiotics and can support the gastrointestinal tract when antibiotics are in use for various bacterial infections, even those not related to the gut. 

These benefits of active S. boulardii hold true in dogs, cats, and horses. It’s even been proven in calves and some mature cattle. 

In total, Brewer’s Yeast and S. boulardii are both safe supplements for our canine, feline, and equine friends. 

*However, when gut health is the goal, S. boulardii will always reign supreme.* 

Finding Out What’s on the Label 

If you’re unsure of what type of yeast is in the product you’re purchasing, don’t reach for your credit card just yet. You want to make absolutely certain of what’s inside first. 

Check out our article about how to make sure you’re grabbing the right product here

In Summary: The Differences Between S. boulardii and S. cerevisiae

Although S. boulardii, like that found in FullBucket products, and Brewer’s Yeast are both beneficial to our animals, there are some key differences to be aware of. 

Here are a few that are most important to share:

  • Where they come from: Brewer’s Yeast is a by-product of the beer brewing industry that is most often deactivated, thus providing a different nutrient profile high in protein, B-vitamins, and chromium. In its active form, Brewer’s Yeast is made up of many strains of S. cerevisiae, but not the more specific S. boulardii that survives the harsh environment of the gastrointestinal tract.

    S. boulardii is a specific strain of S. cerevisiae most often supplemented in its active form. It's widely used as a dietary supplement for its health benefits, particularly for gastrointestinal health.
  • Their uses: Brewer’s Yeast can be used to help balance our animals’ gut, but that’s not what it is primarily used for. The goal with this yeast is often to add B vitamins and chromium to the diet whereas S. boulardii is an active yeast with a plethora of gut health benefits.

    boulardii is recognized for its therapeutic properties, especially in preventing and treating various types of diarrhea, including those caused by antibiotics, as well as other gastrointestinal disorders. It works by inhibiting the growth of harmful bacterial pathogens, enhancing intestinal barrier function, and has anti-inflammatory effects.

A Beneficial Addition to the Diet

While Brewer’s Yeast has health benefits, investing in supplements that contain the more specific strain of Saccharomyces boulardii is even better. 

You can rest assured that S. boulardii, found in all FullBucket products, has been selected based on its primary use to improve gut health parameters in our dogs, cats, and horses. 

Shop horse products here.

Shop cat products here.

Shop dog products here

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