Fungus in Dog Food? Here’s Why That’s Actually Good News
Fungal protein in dog food sounds strange — but a new study suggests it may be a smart, sustainable ingredient worth knowing about. Researchers tested a protein made from a type of fungus and found that dogs digested it well, happily ate food containing it, and showed signs of a healthier gut along the way.
As pet food brands race to find proteins that are gentler on the planet, many are looking beyond chicken and beef. Some are turning to insects. Others to plants. Now, a small but growing group of researchers is looking at something else: single-cell proteins — tiny organisms like fungi and bacteria that can be grown quickly and efficiently. This study is one of the first to put a fungal version under the microscope in real dogs eating real food.
Why Pet Food Companies Are Looking Beyond Meat
Traditional meat-based proteins come with a big environmental footprint. Raising cattle or chicken takes land, water, and energy. That’s why researchers around the world are exploring alternative proteins — ingredients that pack the same nutritional punch but are easier on resources.
Single-cell protein (SCP) is exactly what it sounds like: protein made from single-celled organisms, such as fungi, yeast, or bacteria. These microorganisms can be grown in controlled environments using byproducts from other industries, making them a potentially low-waste option. The challenge is making sure they’re actually good for dogs — that dogs can absorb the nutrients, that it doesn’t upset their stomachs, and that they’ll actually want to eat it.
Before this study, there wasn’t much solid data on how a fungal single-cell protein would perform in dog diets.
How the Study Was Designed
The researchers ran several separate but related experiments, all focused on a fungal protein called Paecilomyces variotii — a type of mold that can be grown and harvested for its protein content. Here’s a plain-language breakdown of what they tested:
- Digestibility trial: 15 adult Beagles were fed diets containing the fungal protein. Researchers measured how well the dogs absorbed nutrients from the food by analyzing what came out the other end. Think of it like checking how much of a meal actually gets used versus passes through unused.
- SCP digestibility trial: A separate group of 12 adult Beagles ate the fungal protein on its own (not mixed into a full diet) to measure how digestible that specific ingredient was by itself.
- Palatability trial: 16 adult dogs were offered a choice between two bowls — one with the new ingredient and one without — to see which they preferred. This is the standard way pet food scientists test whether dogs actually like something.
The fungal protein was included in the diets at levels of 4% and 8% of the total food — moderate amounts, not large quantities.
What the Researchers Found
Digestibility Held Up
Good news on the gut front: including 4–8% fungal protein in the diet had little negative effect on how well dogs digested their food. The dogs were able to absorb nutrients from these diets at levels comparable to standard diets. In plain terms, the fungal ingredient didn’t block or reduce the body’s ability to get what it needs from food.
The Gut Microbiome Shifted in a Positive Direction
Here’s where things get interesting. The researchers also looked at the dogs’ fecal microbiome — the community of bacteria living in the gut — as well as certain chemical byproducts in the stool. Think of the gut microbiome as a tiny ecosystem inside your dog’s digestive tract. When that ecosystem is balanced, it supports digestion, immunity, and overall health.
After eating the fungal protein diet, the dogs showed favorable shifts in their gut bacteria and the chemical byproducts those bacteria produce. In other words, the fungal ingredient appeared to act a little like a prebiotic — feeding the helpful bacteria in the gut and nudging the microbiome in a healthier direction.
Dogs Were Happy to Eat It
Perhaps most importantly for pet owners: the dogs liked it. The palatability trial showed that food containing the fungal protein was accepted just as well as food without it. Dogs didn’t turn their noses up at it or eat noticeably less. That might sound like a small detail, but it’s a critical hurdle for any new ingredient. The healthiest food in the world is useless if your dog won’t touch it.
What This Means for You and Your Dog
You May See Alternative Protein Labels Soon
If you pay attention to pet food labels, you may start seeing ingredients like “single-cell protein,” “mycoprotein,” or unfamiliar scientific names on packaging. This study is part of a growing body of evidence that helps food makers and regulators figure out which alternatives are actually safe and effective.
For now, this research tells us that a fungal protein at moderate levels appears to be a reasonable ingredient — not a red flag. If you’re someone who cares about buying more sustainable pet food, findings like these are a step toward having real options.
What to Look for on the Label
If you’re curious about alternative proteins, keep an eye on:
- Ingredient transparency: Good pet food brands will name specific protein sources, not just list “animal protein” or vague terms.
- AAFCO statements: In the US, look for a statement that the food meets AAFCO (Association of American Feed Control Officials) nutritional standards — this means the diet has been reviewed for completeness.
- Digestibility claims: Some brands publish digestibility data. Now you know what that means and why it matters.
When to Talk to Your Vet
If your dog has a sensitive stomach, known food allergies, or a health condition that affects digestion, it’s always worth checking with your vet before switching foods — regardless of the protein source. This study tested healthy adult dogs, so results may not apply equally to dogs with digestive issues.
Limitations to Keep in Mind
This study was conducted with small groups of adult Beagles in controlled laboratory settings, so the results may not perfectly reflect every dog’s real-world experience. The trials also measured short-term outcomes only — we don’t yet know how dogs fare eating fungal protein over months or years. Puppies, senior dogs, and dogs with medical conditions were not included. More research with larger and more diverse groups of dogs will help confirm these early findings.
The Bottom Line
A series of feeding trials found that a fungal single-cell protein added to dog food at 4–8% levels was well-tolerated by adult dogs. It didn’t meaningfully hurt digestion, dogs ate it willingly, and it appeared to give gut bacteria a gentle boost. That’s a solid result for an ingredient that’s only just beginning to make its way into pet food research.
You don’t need to rush out and change your dog’s food today. But the next time you see “alternative protein” on a pet food label, you’ll have a better idea of what the science actually says — and what questions to ask.
This article summarizes peer-reviewed research for educational purposes. Always consult with your veterinarian for personalized advice about your pet’s health and behavior.