The results are in: KatKin's heat damage study

Pet foods are processed under drastically different conditions (our own scientists even published a paper on this!):

Food processing can improve food safety, texture and aroma. But it can also lead to the degradation of essential nutrients (like lysine) and the formation of compounds known as advanced glycation end-products (AGEs).

Mixed feeding of dry (kibble) and wet (canned, pouch) food remains the most prominent feeding practice reported by cat parents today. However, as cat parents express increased interest in ingredient quality and health claims, the purchasing of newer cat food formats like gently cooked fresh food is increasing.

Advanced glycation end-products are heat-processing byproducts. They form during food processing when amino acids (like lysine) react with sugars in what’s known as the Maillard reaction. The amount of AGEs that form tends to increase with higher temperatures, longer processing times, and greater availability of protein and sugars. When amino acids, like lysine, are involved in the formation of AGEs, they become nutritionally unavailable to the cat. This is of particular nutritional importance, as lysine is an essential amino acid that cats must consume through diet. They need it for normal growth, tissue repair, immune function and overall health.

In humans, higher dietary AGE intake has been linked to an increased risk of chronic diseases, including cardiovascular disease, cancer, metabolic syndrome, overweight and obesity, dementia and cognitive decline, liver disease and chronic kidney disease. While similar associations have been found in rodent studies, very little research exists in companion animals, especially cats. 

While we need to answer how these compounds might impact feline health, as a first step it’s crucial to understand how much are actually in different types of cat foods. Only a handful of studies have looked at AGE levels in pet foods, and even fewer have looked at fresh foods, like KatKin.

We analysed 26 commercial cat foods from the UK and US, covering three diet formats: fresh (n=6), wet (n=10), and dry (n=10). All diets were nutritionally complete for adult maintenance or all life stages and listed chicken as the first named meat ingredient.

And we didn’t just pick random or obscure wet and dry brands. We included both widely purchased mainstream brands, as well as those marketed as premium. For the fresh category, there were only 6 commercially available products that met our criteria at the time of sampling, and all were included. 

We measured the concentrations of three common AGEs: CML, CEL, MG-H1. In addition, we measured the nutritional profile of the diets and the amount of reactive lysine, the nutritionally available form of lysine, they contained.

Our goal was simple: compare AGE levels across three differently processed cat food formats to better understand what cats may actually be exposed to through diet. Here’s what we found.

1) Fresh diets were higher in protein and lower in starch than dry diets

Across the foods we tested:

• Fresh and wet diets both contained more protein and fat than dry diets, while dry diets contained far more starch. 

• Fresh and wet diets also had higher metabolisable energy than dry diets, meaning cats get more usable energy from every bite. 

• More than half the calories in fresh and wet diets come from protein, unlike dry food, where carbs play an equally dominant role. As obligate carnivores, cats have  a high dietary requirement for protein and a limited need for carbohydrates. 

2) Fresh diets delivered the highest average level of available lysine

Across the products tested: 

• Fresh diets consistently had the highest levels of reactive (nutritionally available) lysine. 

• Dry diets had the lowest levels of reactive lysine.

• Wet diets sat in between and showed the widest variability.

That said, all diets tested still exceeded the established minimum lysine requirement for all life stages. But fresh diets, like KatKin, are high in whole meat ingredients, which provide naturally high levels of lysine. Cats require high levels of lysine from their diet to support muscle maintenance, tissue repair, immune function and overall health.

3) Fresh food contains about one-third of the AGEs found in wet food

When we measured the amount of the three AGEs in cat foods, one format stood out.

• Wet diets had the highest concentrations of all three AGE measured, with total AGE levels averaging about 3X higher than both fresh and dry diets in this dataset. 

• The most predominant AGE in wet foods was MG-H1, accounting for roughly 58% of combined AGE total in wet diets. 

• On average, fresh diets had the lowest amount of MG-H1, with dry foods containing about 2X the level of fresh and wet foods containing roughly 8X the MG-H1 level of fresh. 

If you recall from above, fresh and wet formats were actually fairly similar in terms of macronutrient (protein, fat, starch) composition, yet the wet products came out much higher for total AGE levels. That points towards processing intensity being a major contributor to the formation of AGEs in cat foods. 

Despite being processed under high temperatures and pressures, dry diets did not exhibit the same AGE burden as wet diets. Dry foods are only at peak temperatures for a matter of seconds, and their low moisture (~7% in diets tested in this study) and dry texture may limit the chemical reactions that drive AGE formation. Additionally, AGEs form from amino acids (proteins) and sugars, and the lower protein content of dry diets may have further restricted AGE accumulation. So while processing intensity matters, ingredients and formulation likely matter too. 

4) Cats are exposed to higher levels of dietary AGEs than humans

Looking at concentration per kilogram of food is useful, but what really matters to a cat is exposure: how much they would actually consume. So we estimated daily AGE intake for a typical 4 kg adult cat. Again, the same pattern emerged. 

• Wet diets resulted in the highest estimated total AGE intake.

• Estimated intake from wet is >3X higher than fresh and about 2.5X higher than dry.

In humans, higher dietary AGE exposure has been associated with a long list of adverse health effects. While a comparable causal relationship has not been established in cats, available evidence indicates that cats do absorb AGEs, which helps explain why high AGE intake could matter biologically, even if we don’t yet know exactly what that means for long-term cat health.  

We then compared our cat-food intake estimates with published human dietary intake ranges for CML, CEL and MG-H1: 

• Fresh diets provided the lowest estimated AGE exposure among the cat food formats we tested, and sat closest to reported human intake ranges in our exploratory comparison.

• Cat AGE exposure, especially from wet diets, appeared substantial. 

But across all cat food formats, estimated AGE intake was notably higher than humans. As cats are carnivores, and have a high protein requirement, this is not entirely surprising. And while we don’t know the health impact of high AGE consumption in cats at this time, switching from wet to fresh could reduce your cat’s AGE intake by about 69% at equivalent calorie intake.

5) High-temperature sterilisation (like shelf-stable wet food) of KatKin dramatically increased AGEs

We took KatKin Cluck and compared the regular gently-cooked product with a version processed under high-heat sterilisation, just like a shelf-stable wet food.

The result: total AGE increased by 106% in the sterilised version! This confirmed for us that mildly cooking KatKin (like we always do) results in fewer AGEs than the more intensive processing conditions of conventional shelf-stable wet food.

What all this means

KatKin's fresh food is formulated to deliver high levels of naturally available protein while minimising the heat-processing byproducts that form during more intensive cooking methods. Our study found that fresh diets contained the highest levels of reactive lysine of all formats tested, alongside the lowest concentrations of advanced glycation end-products (AGEs).

We will continue formulating our recipes with whole meat ingredients that are naturally high in essential nutrients and protein, and cook them below 100°C to help limit excessive nutrient degradation and the formation of potentially harmful heat-processing byproducts. 

These findings have now been peer reviewed and accepted for publication in the Journal of Animal Science, one of the leading journals in animal health & research. By sharing our research openly with the scientific and veterinary communities, we hope to advance understanding of how food processing influences nutrient quality and heat-derived compounds in commercial cat foods.

At KatKin, we're committed to investing in scientific research that helps improve feline nutrition and supports longer, healthier lives for cats.