According to Gram Research analysis, the type of carbohydrate in cat food significantly affects how well cats digest protein. A 2026 study of 117 cats found that duck, chicken, and salmon proteins were digested most efficiently (83-86%), while rice and corn as carbohydrate sources supported better protein digestion than wheat or potato. The research shows that protein and carbohydrate sources work together in cat food, meaning the combination matters more than individual ingredients alone.
A new study of 117 cats found that the type of carbohydrate in cat food affects how well cats digest protein. Researchers tested 12 different cat food recipes using different proteins (like chicken, duck, and salmon) combined with different carbs (like rice, corn, and wheat). They discovered that rice and corn helped cats digest protein better than wheat or potato. The findings suggest pet owners should pay attention to both the protein source and the carbohydrate source when choosing cat food, since they work together to affect nutrition.
Key Statistics
A 2026 study of 117 domestic cats found that duck protein had the highest digestibility at 86.36%, followed by chicken at 85.72% and salmon at 83.05%, compared to beef and cricket at approximately 75%.
According to research reviewed by Gram, when paired with chicken protein, rice and corn supported protein digestibility of 85.72% and 76.82% respectively, while wheat, potato, and sweet potato resulted in lower digestibility rates of 72-75%.
A 2026 feline nutrition study identified seven amino acids (alanine, serine, valine, threonine, histidine, phenylalanine, and isoleucine) that strongly tracked with overall protein digestion, with phenylalanine showing the strongest correlation (R² = 0.89).
Research on 117 cats found that rice, despite having the lowest carbohydrate digestibility at 7.71%, produced the highest efficiency ratio of 11.12, suggesting that food structure and ingredient interactions matter more than individual ingredient digestibility.
The Quick Take
- What they studied: Whether the type of carbohydrate in cat food changes how well cats can digest and use protein
- Who participated: 117 domestic Korean short-haired cats that ate different test diets for two weeks before measurements were taken
- Key finding: Duck, chicken, and salmon proteins were digested best (83-86%), while beef and cricket were digested less well (75%). Rice and corn as carbohydrate sources helped cats digest protein better than wheat, potato, or sweet potato.
- What it means for you: If you have a cat, the combination of protein and carbs in their food matters. Choosing foods with chicken, duck, or salmon paired with rice or corn may help your cat get more nutrition from their meals. However, more research is needed before making major diet changes.
The Research Details
Researchers created 12 different cat food recipes to test how protein and carbohydrate sources affect digestion. They used 117 cats and gave each cat a two-week adjustment period to get used to the new food before measuring how much nutrition the cats actually digested. The study tested six different protein sources (chicken, duck, salmon, pollock, beef, and cricket) and six different carbohydrate sources (rice, corn, potato, tapioca, sweet potato, and wheat). By measuring what came out of the cats’ bodies, scientists could calculate how much protein and amino acids (the building blocks of protein) the cats’ bodies actually absorbed and used.
This approach is called ‘apparent total tract digestibility’ or ATTD, which is a standard way to measure how much nutrition an animal gets from food. The researchers also looked at something called an ’efficiency ratio’ that shows the relationship between how well protein was digested compared to how well carbohydrates were digested. They paid special attention to seven specific amino acids that seemed to track closely with overall protein digestion.
Cats are carnivores, meaning they naturally eat meat and need lots of protein. However, most dry cat foods contain carbohydrates because they help hold the food together during manufacturing. This study matters because it shows that the carbohydrate source isn’t just filler, it actually affects how well cats can digest and use the protein in their food. Understanding these interactions helps pet food companies make better formulas and helps cat owners understand what their pets are actually getting from their meals.
This study is a solid research article published in a peer-reviewed veterinary science journal. The sample size of 117 cats is reasonably large for this type of research. The study used a controlled design where researchers carefully measured what went in and what came out, which is a reliable method. However, the researchers themselves note that their ’efficiency ratio’ is preliminary and needs more testing before it can be used to make strong claims about protein quality. The study was conducted in a controlled setting, so results might differ slightly in real-world situations.
What the Results Show
When researchers looked at different protein sources, duck came out on top with 86.36% digestibility, followed closely by chicken at 85.72% and salmon at 83.05%. Beef and cricket proteins were digested less efficiently at around 75%. This means cats’ bodies can use duck, chicken, and salmon protein more completely than beef or cricket protein.
The carbohydrate source also made a big difference. When paired with chicken protein, rice and corn allowed cats to digest protein at 85.72% and 76.82% respectively. In contrast, wheat, tapioca, potato, and sweet potato resulted in lower protein digestibility rates of 75.23%, 74.49%, 72.52%, and 72.04%. Interestingly, while rice had the lowest carbohydrate digestibility itself (only 7.71%), it actually helped cats digest protein the best overall.
The researchers identified seven specific amino acids, alanine, serine, valine, threonine, histidine, phenylalanine, and isoleucine, that closely tracked with overall protein digestion. This suggests these amino acids could be useful markers for understanding protein quality in cat foods. The strongest relationships were found with phenylalanine, alanine, and isoleucine.
The study found that the relationship between protein and carbohydrate sources is complex. Rice, despite being poorly digested as a carbohydrate itself, actually supported the best protein digestion. This suggests that the structure of the food matrix, how ingredients are physically arranged and processed together, matters more than individual ingredient digestibility. The efficiency ratio (the relationship between protein and carbohydrate digestion) showed strong mathematical relationships with certain amino acids, particularly phenylalanine with an R² of 0.89, alanine with 0.87, and isoleucine with 0.85. These high correlations suggest these amino acids might be useful indicators of overall protein quality in feline diets.
This research builds on existing knowledge that cats are obligate carnivores requiring high protein intake. Previous studies have shown that protein source matters for cats, but this is one of the first studies to systematically examine how carbohydrate sources interact with protein sources in cat nutrition. The findings align with general principles of pet nutrition that ingredient combinations matter, not just individual ingredients. However, the specific interactions discovered here, particularly that rice supports protein digestion despite poor carbohydrate digestibility, add new insights to the field.
The researchers themselves note several important limitations. First, the efficiency ratio they developed is preliminary and needs more validation before it can be reliably used to compare cat foods. Second, this study measured what came out of cats’ bodies but doesn’t directly measure how well cats actually use the amino acids after absorption, that’s a more complex process. Third, the study was done in a controlled laboratory setting with specific cat breeds and ages, so results might vary with different cats or in home environments. Finally, the study doesn’t tell us whether these digestibility differences actually matter for cats’ health in the long term.
The Bottom Line
Based on this research, cat owners may want to consider foods containing chicken, duck, or salmon proteins paired with rice or corn as carbohydrate sources, as these combinations showed the best protein digestibility in this study (moderate confidence). However, this is one study, and digestibility alone doesn’t determine whether a food is best for your cat. Consult your veterinarian before making major diet changes, especially if your cat has health issues. The research suggests that ingredient combinations matter, not just individual ingredients.
Cat owners interested in optimizing their pet’s nutrition should pay attention to these findings. Pet food manufacturers can use this information to improve formulations. Veterinarians may find this helpful when recommending foods to clients. People with cats that have digestive issues or nutrient absorption problems might benefit from understanding these interactions. However, if your cat is healthy and thriving on their current food, there’s no urgent need to change based on this single study.
If you switched your cat to a food with better protein digestibility, you wouldn’t see dramatic changes overnight. It typically takes 2-4 weeks for cats to fully adjust to a new food and for any nutritional benefits to become apparent. You might notice improvements in coat quality, energy levels, or digestion over several weeks to months, but individual cats vary significantly.
Frequently Asked Questions
Does the type of carbohydrate in cat food really affect protein digestion?
Yes. A 2026 study of 117 cats showed that rice and corn as carbohydrate sources supported better protein digestion (76-86%) compared to wheat, potato, or sweet potato (72-75%). The carbohydrate source affects how well cats’ bodies can use the protein in their food.
What’s the best protein source for cats based on this research?
Duck showed the highest digestibility at 86.36%, followed by chicken at 85.72% and salmon at 83.05%. These three proteins were digested significantly better than beef or cricket (both around 75%) in the study of 117 cats.
Should I change my cat’s food based on this study?
Not necessarily without consulting your veterinarian. While this research suggests certain protein and carbohydrate combinations support better digestion, one study isn’t definitive. If your cat is healthy and thriving, there’s no urgent need to change. Discuss any diet modifications with your vet first.
How long does it take to see benefits if I switch cat food?
Cats typically need 2-4 weeks to adjust to new food. You might notice improvements in coat quality, energy, or digestion over several weeks to months, but individual cats respond differently. Monitor your cat’s stool quality and overall health during the transition.
Why does rice help protein digestion if cats don’t digest rice well?
This study found that rice, despite poor carbohydrate digestibility (7.71%), actually supported the best protein digestion overall. This suggests that how ingredients are physically combined in food (the food matrix) matters more than how well individual ingredients are digested separately.
Want to Apply This Research?
- Track your cat’s current food ingredients (protein source and carbohydrate source) and monitor digestive health markers: stool quality (1-5 scale), energy level (1-5 scale), and coat condition (1-5 scale) weekly. Compare baseline measurements to measurements after any diet changes.
- Use the app to log your cat’s current food and set a reminder to review the ingredient list. If considering a diet change, use the app to track which protein and carbohydrate sources are in candidate foods, then monitor your cat’s response over 4-6 weeks with weekly check-ins on digestion and overall health.
- Create a long-term nutrition profile for your cat that includes current food ingredients, digestive health scores, and energy levels. Set monthly reviews to assess whether current food is supporting optimal digestion. If switching foods, use the app to document the transition period and track any changes in stool quality, appetite, or coat condition.
This research provides scientific information about protein and carbohydrate digestibility in cat foods but should not replace professional veterinary advice. Individual cats have different nutritional needs based on age, health status, activity level, and medical conditions. Before making significant changes to your cat’s diet, consult with your veterinarian. This study measured nutrient digestibility in a controlled setting and does not establish long-term health outcomes or definitively prove that higher digestibility always results in better health. The efficiency ratio described in this study is preliminary and requires further validation before clinical application.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.
