This Is the New 'Gold Standard' Pet Food Protein? Seriously, Don't Be Conned

Analysis by Dr. Karen Shaw Becker

dog and cat eating animal meat

Story at-a-glance -

  • The processed pet food industry is preparing to position dried yeast — a waste product of ethanol production — as a “gold standard” pet food protein
  • Yeast is a fungus, and neither fungi nor plants have the complete amino acid profile dogs and cats require; how much animal protein dried yeast will displace in pet food formulas is unknown
  • Cats, as true carnivores, must eat animal meat to survive; dogs, as facultative carnivores also require animal tissue and organs to be optimally healthy
  • Research shows that too much poor-quality protein and too little protein can be damaging to the body
  • Yeast in pet food has the potential to exacerbate yeast infections in pets

Here's a recent pet food industry journal headline that caught my attention (and not in a good way): "Dried yeast may provide 'gold standard' pet food protein."1 Dried yeast is now the leading pet food protein? Seriously? A few excerpts from the article:

"Dried yeast left over from the production of ethanol, used as a biofuel and in other industries, may provide palatability enhancement in pet food on par with brewers' yeast."

Raise your hand if you're a pet parent who wants waste from the production of ethanol added to your dog's or cat's food to improve the taste. Anyone? I didn't think so.

"… [D]ried yeast provides proteins and their building blocks, amino acids, which means the desiccated fungus may serve as a novel protein source to replace animal byproducts in dog and cat food formulations."

It appears the processed pet food industry is planning to tout dried yeast in their products as a novel protein. Now, I think most pet owners assume when they see the term "novel protein," it means meat from an exotic or less common food animal, for example, kangaroo, venison or even rabbit.

I'm pretty sure if you saw a pet food advertised as containing a novel protein, presumably designed for dogs or cats with food sensitivities, you'd never guess you were buying a product containing dried yeast versus animal meat.

The proteins found in plants and fungi are not appropriate substitutes for animal tissue and organs in the diets of carnivorous pets. Dogs and cats are carnivores who need 22 amino acids to be healthy. Dogs can synthesize 12 of the 22; cats can synthesize 11. The remaining amino acids must come from the food pets eat, so if dried yeast is replacing animal protein (even in the form of byproducts), it's a problem.

Cats Are Strict Carnivores Who MUST Eat Animal Meat and Organs

Cats must eat animal meat and organs to meet their nutritional needs, and as I just mentioned, plant- and fungus-based proteins simply aren't a good substitute. Felines lack the specific enzymes necessary to use non-animal proteins as efficiently as animal proteins. The proteins derived from animal tissue contain a complete amino acid profile. Amino acids are the building blocks of protein. Proteins derived from plants and fungi don't contain all the amino acids critical for the health of an obligate carnivore.

Dogs Are Facultative Carnivores Who SHOULD Eat Animal Meat and Organs

A major pet food company conducted a study several years ago that examined how the type of protein fed to adult and senior dogs affected body composition (muscle versus fat). The dogs were fed diets with varying amounts of protein from chicken and corn gluten meal.2

Dogs in one group were fed a diet of exclusively chicken; the rest were fed diets with decreasing amounts of chicken and increasing amounts of corn gluten meal. Compared with the dogs fed 100 percent chicken, the dogs fed the other diets had:

  • A decrease in lean tissue
  • An increase in body fat
  • Decreased levels of blood proteins that are universal markers of a well-nourished body

The same company did another study focused on the decline in body composi­tion and muscle-specific proteins in aging dogs.3 Senior dogs were fed a 32 percent chicken-based diet, a 32 percent chicken and corn gluten meal diet, or a 16 percent chicken-based diet.

The dogs fed the 32 percent chicken-based diet had better body composition than healthy young adult dogs, and identical muscle-specific protein levels. Neither of the other two groups of senior dogs (those fed chicken + corn gluten meal or the diet with just 16 percent chicken) had similar results.

The pet food company concluded that feeding dogs diets containing primarily animal-based protein sources provides several benefits, including:

  • Helps to maintain muscle mass
  • Reverses some age-related changes in skeletal muscles in senior dogs
  • Enhances the long-term health and well-being of both adult and senior dogs

Interestingly, despite the company's conclusion years ago that animal-based protein is the best type of protein for dogs, it doesn't appear they've incorporated their study findings into their dog food formulas. A quick glance at the ingredient lists for several of the company's senior and mature adult dog foods reveals corn meal and a variety of other plant-based ingredients at the top of the list.

Why the Right Kind of Protein in the Right Amount Is so Important to Your Pet's Health

Proteins are often called the "building blocks of life," essential to the survival of animals, and found in every organism on the planet. Here are some facts about protein from the Weston A. Price Foundation:4

  • It is essential to a healthy heart and body
  • Animal sources of protein, including eggs, are better nutritionally because they contain all the essential amino acids (amino acids are called the "building blocks of protein")
  • Too much poor-quality protein and too little protein can be damaging to the body
  • Protein isn't stored in the body like fat — it must be eaten daily
  • The one nutritive substance that stands before all others is protein

Your pet's body is literally made of protein, including his bones, muscles, arteries, veins, skin, hair and nails. The tissues of his heart, brain, liver, kidneys and lungs are made of proteins. Proteins oxygenate the blood and transport fat and cholesterol throughout your pet's body. The enzymes in proteins help to digest the food he eats, synthesize essential substances and break down waste products.

Proteins in combination with sterols produce hormones that regulate the sensitive chemical changes that take place constantly within your pet's body. And the chromosomes that will be passed on to your pet's offspring (and that were passed on to him) include proteins in their structure.

Why Are We Feeding Yeast to a Pet Population Prone to Yeast Infections?

Yeast infections of the skin and ears are very common in pets, primarily dogs, which is another reason I don't like diets containing additional yeast. Dr. Roger Henderson states, "Some people with chronic yeast infections do report that their symptoms appear to improve if they change to a low-yeast diet," and I have found this to be true with pets, as well.

A normal amount of yeast becomes an infection when the organism begins reproducing uncontrollably. When the yeast reproduction gets out of control, the organisms invade and colonize areas of the body and skin beyond those where they normally live, and in higher numbers.

Most pets with yeast infections have immune system imbalances that inhibit the body's ability to control the yeast overgrowth. Yeast infections often occur during or after antibiotic therapy because the drugs have reduced the beneficial bacterial levels necessary to maintain healthy skin defenses.

Yeast can also be a significant problem for immunosuppressed animals, including those born immunoglobulin deficient. There are also certain drugs, including steroids and chemotherapeutic agents, which suppress the immune system and can open the door to yeast infections.

I also see lots of yeast infections associated with allergies. An allergy is an immune system over-reaction, and many veterinarians use immunosuppressive steroids like prednisone, dexamethasone and cortisone to mute or turn off the immune response, making it incapable of managing normal flora levels. This can lead to yeast overgrowth.

The nutrition your pet receives either supports his immune system to keep yeast growth under control, or it does the opposite and triggers or exacerbates yeast overgrowth. I recommend an anti-inflammatory (starch-free) diet for all pets, and especially those with a tendency to develop yeast infections.

Yeast uses sugar as a source of energy. We know that carbohydrates break down into sugar, which is why it's so important remove sugar (aka high-glycemic carbs) from the diet. And remember that dietary sugar isn't just the white stuff — it's also honey and high-fructose corn syrup. Even white and sweet potatoes can feed a yeast problem, along with the tapioca found in grain-free dry foods.

Feeding your dog or cat a nutritionally balanced, species-appropriate, fresh food diet will help keep healthy flora levels in balance. If your pet currently has or has ever had a yeast infection, I also recommend adding a few natural antifungal foods to the diet, for example, small amounts of fresh garlic, thyme, parsley and oregano to help reduce the level of yeast naturally.

Offering fermented veggies can also be very beneficial. Raw, unfiltered apple cider vinegar and coconut oil have natural antifungal properties and can be added directly to your pet's meals.