If you’ve ever caught your dog eating poop, your first reaction was probably disgust.
You’re not alone.
The behavior even has a scientific name: coprophagia.
And while it might seem strange or purely behavioral… there’s actually a biological reason many dogs do it.
In some cases, your dog’s poop may contain nutrients their body didn’t absorb the first time around.
And because of what happens during digestion, that poop can become partially fermented by gut bacteria.
Which means, biologically speaking, it can sometimes be more nutritionally available than the food that originally went into the bowl.
Let’s explain why.
What Actually Happens When Your Dog Digests Food
When your dog eats a meal, digestion begins immediately.
Food moves through the stomach and into the intestines where enzymes and bacteria break it down.
But here’s the important part:
Not everything gets absorbed.
Even high-quality dog foods often leave behind:
• undigested proteins
• fibers that weren’t broken down
• minerals bound inside plant material
• nutrients trapped in complex carbohydrates
These leftovers travel into the large intestine, where trillions of bacteria begin feeding on them.
This microbial activity is essentially fermentation.
During fermentation, gut microbes break down leftover nutrients and produce beneficial compounds such as:
• short-chain fatty acids
• certain B vitamins
• vitamin K
• additional enzymes and metabolites
This microbial fermentation process is a normal part of digestion.
But it also means something surprising.
Some nutrients are actually released late in the digestive process… after the small intestine has already absorbed most nutrients.
So they end up leaving the body in stool.
Why Dogs Are Attracted to Fresh Stool
Research shows that most dogs that eat stool prefer fresh poop that is less than two days old.
That detail matters.
Fresh stool still contains:
• active microbes
• digestive enzymes
• partially fermented nutrients
From a dog’s perspective, that smell can signal nutrient density.
In fact, stool can contain undigested food particles and nutrients that were not absorbed during digestion, which may explain why some dogs attempt to eat it again.
Veterinary research also suggests dogs may eat stool when they:
• lack certain nutrients
• have trouble absorbing nutrients
• have imbalances in their gut bacteria
In other words…
Sometimes dogs eat poop because their body is looking for something it didn’t fully get the first time.
Nature Already Uses This Strategy
Believe it or not, many animals rely on this exact process.
Rabbits, rodents, and other mammals routinely eat a special form of fermented stool to obtain nutrients created by gut bacteria.
This allows them to absorb:
• microbial proteins
• B vitamins
• fermentation byproducts
• additional energy from fiber
While dogs don’t rely on this process the way rabbits do, the instinct to consume stool may be a leftover biological strategy to recover nutrients.
The Real Problem: Modern Diets Lack Fermented Nutrition
Historically, dogs consumed a much wider variety of foods.
Their diets included:
• the gut contents of raw prey
• partially digested plant material
• soil microbes
• fermented organic matter
Today, most dogs eat highly processed kibble.
Even high-quality kibble diets are typically:
• heat processed
• low in natural microbes
• lacking fermented nutrients
That means the gut microbiome has to do more work to break down food.
And if the gut ecosystem isn’t balanced, dogs may experience:
• poor nutrient absorption
• digestive discomfort
• microbiome imbalances
Which may increase behaviors like grass eating or poop eating.
Why Fermented Foods Help
Fermented foods contain beneficial microbes and nutrients that have already been partially broken down.
This makes them easier for the body to use.
Fermentation can:
• unlock nutrients trapped in plants
• support beneficial gut bacteria
• improve digestion and nutrient absorption
• help restore microbial balance
In other words…
Fermented foods can provide many of the same biological benefits that dogs instinctively seek when they eat stool.
Without the poop.
A Better Way to Support Your Dog’s Gut
If your dog eats poop, it’s worth asking an important question:
What is their body trying to get?
Sometimes the answer is simple.
Their gut may need more support.
Adding fermented whole foods can help provide:
• beneficial microbes
• digestive enzymes
• bioavailable nutrients
• microbial diversity
All of which support a healthier digestive system.
And when the gut is functioning properly, many dogs naturally lose interest in eating stool.
The Bottom Line
Poop eating might seem gross…
But biologically, it can be a signal.
Sometimes it means your dog’s body is searching for nutrients, microbes and digestive support
The good news is you don’t have to let them find it in the backyard.
Providing fermented foods in their diet can support the gut in a way that’s closer to how digestion works in nature.
And that can help break the cycle of poop eating for good.