The Risks of High-Carbohydrate and Legume-Heavy Diets in Dogs and Cats

Over the past two decades, many commercial pet foods have shifted toward formulas high in carbohydrates and plant-based proteins. Ingredients like peas, lentils, chickpeas, and other legumes are now common in dog and cat foods, particularly in grain-free diets.

While these ingredients are inexpensive and useful for manufacturing kibble, growing research and veterinary concern suggest that high-carbohydrate, legume-heavy diets may pose health risks for dogs and cats.

Understanding how these diets differ from what dogs and cats evolved to eat can help pet owners make more informed choices.

Dogs and Cats Are Built for Animal Protein

Dogs and cats are both classified as carnivores, though dogs are considered facultative carnivores while cats are obligate carnivores.

Their digestive systems evolved to process:

• Animal muscle meat

• Organs such as liver and heart

• Bone and connective tissue

• Small amounts of plant material from prey stomach contents

What they did not evolve to consume in large amounts are concentrated carbohydrates like starches and legumes.

Unlike humans, dogs and cats:

• Produce limited amylase enzymes for starch digestion

• Have short digestive tracts designed for animal protein

• Depend on animal-based nutrients such as taurine, arachidonic acid, and vitamin A

When large portions of the diet are replaced with plant ingredients, nutritional imbalances can occur.

Why Legumes Became Popular in Pet Food

Legumes such as peas, lentils, and chickpeas became widely used in pet foods for several reasons:

• They are inexpensive sources of protein

• They help maintain kibble structure during extrusion

• They replace grains in “grain-free” formulas

• They increase the protein percentage on the label

However, plant protein is not nutritionally equivalent to animal protein for carnivorous animals.

Plant proteins lack key amino acid profiles and often contain anti-nutritional compounds that can interfere with digestion and nutrient absorption.

Possible Links to Dilated Cardiomyopathy (DCM)

In 2018, veterinary cardiologists began reporting an increase in canine dilated cardiomyopathy (DCM) in dogs eating certain diets.

DCM is a serious heart condition where the heart muscle becomes enlarged and weakened, reducing its ability to pump blood effectively.

Many affected dogs were eating diets that were:

• Grain-free

• High in legumes such as peas or lentils

• High in plant protein concentrates

The U.S. Food and Drug Administration (FDA) launched an investigation into these reports.

While the research is still ongoing, many veterinary nutrition experts believe legume-heavy diets may interfere with taurine metabolism, an amino acid essential for heart function.

Some possible mechanisms being studied include:

• Reduced taurine absorption

• Increased taurine loss through bile

• Altered gut microbiome metabolism

• Dilution of animal protein sources

Cats are particularly sensitive to taurine deficiencies because they cannot synthesize it efficiently on their own.

Carbohydrates and Metabolic Health

Most dry kibble diets contain 30–60% carbohydrates due to manufacturing requirements.

For comparison:

• A natural prey diet for carnivores typically contains less than 5–10% carbohydrates.

High carbohydrate intake may contribute to several metabolic issues in pets.

Potential health concerns include

• Obesity

• Insulin resistance

• Type 2 diabetes (especially in cats)

• Chronic inflammation

• Dental disease

Cats are especially vulnerable because they evolved to run on protein and fat rather than glucose.

Anti-Nutrients in Legumes

Legumes contain natural defense compounds known as anti-nutrients, including:

• Phytates

• Lectins

• Protease inhibitors

These compounds can interfere with mineral absorption and digestion.

Although processing reduces some of these compounds, high levels of legumes in the diet may still impact nutrient availability.

The Importance of Animal-Based Nutrition

High-quality animal ingredients provide nutrients in their most bioavailable form.

Examples include:

• Taurine from heart muscle

• Vitamin A from liver

• Essential fatty acids from animal fat

• Highly digestible protein from muscle meat

These nutrients are difficult or impossible to replicate using plant-based ingredients alone.

For this reason, many veterinarians and animal nutrition researchers emphasize the importance of diets that prioritize animal protein and whole-food ingredients.

What Pet Owners Should Look For

Pet owners evaluating a diet for their dog or cat may want to consider several factors.

Ingredient priorities

Look for diets where the primary ingredients include:

• Named animal meats

• Organ meats

• Bone or calcium sources

Ingredients to evaluate carefully

Large amounts of:

• Peas

• Lentils

• Chickpeas

• Pea protein or potato protein concentrates

These ingredients are not inherently harmful, but they should not dominate the formula.

A Growing Interest in Whole-Food Pet Nutrition

As awareness grows about pet nutrition, many pet owners are exploring alternatives to highly processed kibble diets.

These options include:

• Fresh food diets

• Gently cooked foods

• Freeze-dried raw diets

• Biologically appropriate raw feeding (BARF)

These approaches aim to more closely mimic the nutrient profile of a natural carnivore diet.

The Bottom Line

Dogs and cats thrive on diets centered around animal protein and natural nutrients.

While carbohydrates and plant ingredients can serve a role in small amounts, diets dominated by starches and legumes may not provide the same nutritional benefits as animal-based foods.

Ongoing research continues to explore the long-term health effects of these ingredients, but many experts agree that prioritizing species-appropriate nutrition is a safer approach for long-term health.

References

U.S. Food and Drug Administration.
Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy.

Freeman LM, Stern JA, Fries R, Adin DB, Rush JE.
Diet-associated dilated cardiomyopathy in dogs: What do we know?
Journal of the American Veterinary Medical Association.

Zoran DL.
The carnivore connection to nutrition in cats.
Journal of the American Veterinary Medical Association.