Shun NagaiCats are obligate carnivores that naturally rely on protein and fat as their primary energy sources, and carbohydrates are not nutritionally essential in their dietary requirements. This is because cats possess a strong capacity for gluconeogenesis—producing the glucose they need in the liver from amino acids and fats—allowing them to survive without consuming dietary carbohydrates.
However, in the manufacturing of modern dry cat food (kibble), carbohydrates play an extremely important role. The main reason is that starch contained in carbohydrates is indispensable as a “structural forming agent” during the high-temperature, high-pressure extrusion process, where it binds other ingredients together and creates the characteristic shape and texture of kibble.
In addition, when carbohydrates are properly heat-processed (gelatinized), they can become a highly digestible and efficient energy source even for cats. In this article, we scientifically explain cats’ physiological characteristics and the limitations of carbohydrate metabolism, clarify the technical role of carbohydrates in dry food production, compare major carbohydrate ingredients, and provide practical formulation design guidelines.
Physiological characteristics of cats and limitations of carbohydrate metabolism
To discuss carbohydrate utilization in cat food, it is essential to understand cats’ unique physiology and metabolic systems. This understanding is a fundamental prerequisite for designing safe and effective formulations.
Through their evolution as carnivores, cats have developed a physiology with limited capacity to utilize carbohydrates. Therefore, formulation designs that ignore these physiological traits can carry health risks for cats.
Below are the key physiological constraints related to carbohydrate utilization in cats.
Digestive system adapted for carnivory
Compared with omnivorous dogs, cats have a shorter digestive tract, specialized to efficiently digest and absorb diets high in protein and fat. This anatomy suggests that cats are less suited to slowly breaking down and fermenting complex carbohydrates over time.
Lack/insufficiency of carbohydrate-digesting enzymes
Cats do produce pancreatic amylase (though generally less than dogs and omnivores), but unlike dogs, they do not have salivary amylase. As a result, cats are often considered less capable of digesting large amounts of carbohydrates at once.
Limits in carbohydrate (glucose) metabolism
In the feline liver, the activity of glucokinase—an enzyme important for taking up glucose in response to rising blood glucose—is low. This creates broader limitations in the ability to metabolize dietary carbohydrates.
High baseline gluconeogenesis
As noted above, cats constantly maintain active gluconeogenesis, synthesizing glucose in the liver from amino acids (protein) and glycerol (fat), even when they do not consume dietary carbohydrates. This is strong physiological evidence that carbohydrates are not an essential energy source for cats.
Risks of excessive intake
Because of these physiological constraints, if cats consume carbohydrates beyond their processing capacity, the risk increases for gastrointestinal issues such as diarrhea and bloating due to poor digestion, as well as potential blood glucose abnormalities when carbohydrate load exceeds metabolic limits.
These constraints mean that the “tolerable range” of carbohydrates in cat food formulation can be relatively narrow, and the precision of ingredient selection and processing technology becomes a direct determinant of product success.
That said, as explained in the next section, appropriate manufacturing technology can help overcome these limitations and allow carbohydrates to be used safely and beneficially in cat food.
The technical role of carbohydrates in manufacturing
If carbohydrates are not nutritionally essential for cats, why are they major components in many dry foods? The answer lies in the fact that carbohydrates are essential not only as an energy source but also as a physical “structural forming agent” required to create kibble’s unique shape and texture.
The role of carbohydrates (starch) in the extrusion process can be understood through the following technical aspects.
Function as a structural forming agent
In dry food manufacturing, ingredients are mixed and passed through an extruder under high temperature and pressure. During this process, starch undergoes structural changes due to heat and moisture: its crystalline structure breaks down and it becomes gel-like.
This is called gelatinization. Gelatinized starch becomes highly viscous and functions as a “binder,” gluing together other ingredient particles such as meat meals and fats.
In addition, starch gelatinizes inside the extruder under high temperature and pressure, and when the material exits the die, pressure drops suddenly and the product expands. Gelatinized starch stabilizes the porous, sponge-like structure at this moment, creating the crunchy texture characteristic of kibble.
Importance of the degree of gelatinization
The extent to which starch has gelatinized is expressed as the “degree of gelatinization,” and it is an extremely important parameter that determines finished product quality.
Benefits of a high degree of gelatinization ※target guideline: 90% or higher
- Improved digestibility: Gelatinized starch is more readily broken down by digestive enzymes, allowing cats to use it efficiently as an energy source.
- Improved palatability: Proper expansion and favorable texture are reported to increase palatability for cats.
- Better kibble expansion: Greater gelatinization improves expansion, helping achieve appropriate density and texture.
Drawbacks of a low degree of gelatinization
- Poor digestion: Undigested starch passes through the small intestine.
- Abnormal fermentation in the large intestine: Gut bacteria ferment undigested starch, causing gas, diarrhea, and soft stools. Studies report that lower gelatinization is associated with increased volatile fatty acids in feces; this can be interpreted as an unfavorable indicator reflecting abnormal fermentation driven by undigested starch.
Relationship with processing conditions
The degree of gelatinization is strongly influenced by extrusion conditions, particularly the thermal energy applied to the ingredients (Specific Thermal Energy: STE).
Studies show that higher STE improves gelatinization and kibble expansion, and as a result, can increase palatability. Conversely, low-STE conditions can lead to insufficient gelatinization, increased fermentation in feces, and potentially greater digestive burden.
In conclusion, carbohydrates that have been properly gelatinized through manufacturing technology can overcome cats’ physiological constraints and become a highly digestible energy source (with digestibility exceeding 93%). Under appropriate extrusion conditions, digestibility may reach 98% or higher for starch sources such as white rice or cassava, as some reports indicate.
Therefore, the value of carbohydrates is determined not only by the intrinsic properties of the ingredient, but also by how effectively it is processed using advanced manufacturing technology. Next, we compare the characteristics of specific carbohydrate ingredients.
Comparative analysis of major carbohydrate ingredients
| Ingredient | GI Category | Gelatinization | Dietary Fiber | Key Benefits | Points to Watch |
|---|---|---|---|---|---|
| White rice | High GI (approx. 70–90; varies by variety and polishing) | High | Very low | Highly digestible; rapid energy supply | Tends to increase blood glucose quickly; monitor glycemic load and stool quality at high inclusion levels |
| Corn | Medium GI (approx. 52–60) | Good (requires slightly higher temperature range) | Moderate (higher if whole grain) | Good processing performance; contributes to expansion | Glycemic response may vary depending on ingredient form and processing |
| Wheat | Low to medium GI (approx. 41–55) | Good | Moderate | Gluten-derived binding improves kibble formation; contains micronutrients | Some markets prefer wheat-free formulas (true allergy is rare) |
| Potato | High GI (when warm, often exceeds 75–100) | Very high | Low | Excellent gelatinization; enhances kibble physical structure | Rapid blood glucose response; high inclusion may soften stools |
| Tapioca (cassava) | Medium to high GI (approx. 56–90) | Very high | Very low | Highly digestible; neutral flavor; suitable for grain-free design | Nutritionally almost pure starch; high inclusion may cause loose stools |
| Legumes (peas, lentils) | Low GI (e.g., peas ~48; lentils ~29) | Moderate | High (consider soluble/insoluble balance) | Low GI; rich in dietary fiber; plant protein source | Resistant starch may reduce digestibility at high inclusion levels |
When designing a dry food formula, selecting the optimal carbohydrate sources requires a multi-angle evaluation of nutritional and physicochemical properties across a wide range of ingredients. Here we compare six major carbohydrate ingredients.
To make this comparison more actionable, below is a detailed discussion of each ingredient.
1. White rice (milled rice)
Characteristics
White rice is a representative high-GI ingredient (approximately 70–90). It contains extremely little dietary fiber, and because of starch characteristics (largely amylopectin), it gelatinizes easily with heat processing and shows high digestibility.
Formulation benefits and cautions
Because it gelatinizes well and is highly digestible, it is easy to use as a stable energy source. However, due to its high GI, it may raise blood glucose rapidly, so high inclusion requires careful consideration of glycemic load.
2. Corn
Characteristics
Corn has a mild sweetness and a medium GI (about 52–60). Its gelatinization behavior is good, and during extrusion it contributes to kibble expansion.
Formulation benefits and cautions
It is widely used because of stable quality and strong processing suitability. Some studies report higher glycemic response compared with other carbohydrate sources, while other studies describe a relatively moderate response—suggesting that form and degree of processing can affect outcomes.
3. Wheat
Characteristics
Wheat has a relatively lower GI (about 41–55). It contains gluten, which improves stickiness and expansion, providing manufacturing advantages. It also contains vitamins and minerals.
Formulation benefits and cautions
Wheat offers excellent binding properties and helps improve kibble physical quality. Absorption tends to be slower than rice or corn.
4. Potato
Characteristics
Potato is a high-GI ingredient similar to rice (generally 75 or higher). It is composed almost entirely of starch, with high amylopectin content, resulting in very strong gelatinization and substantial improvements in kibble density and expansion.
Formulation benefits and cautions
It is often used as a main energy source in grain-free products and has excellent processing performance. However, because it is high GI, attention is needed regarding rapid glycemic response. The glycemic load of potato-containing foods is considered to vary depending on the balance with protein and fat.
5. Tapioca (cassava)
Characteristics
Tapioca is a starch derived from cassava root and contains almost no dietary fiber. It has extremely high gelatinization capacity and is widely used, alongside potato, in grain-free products as an alternative carbohydrate source.
Formulation benefits and cautions
Studies confirm digestibility comparable to white rice. GI data vary, but some trials report more moderate glycemic responses compared with corn or white rice.
6. Legumes (peas, lentils)
Characteristics
Legumes have a very low GI (peas around 48, lentils around 29). They are rich in dietary fiber and plant protein. Because part of their starch acts as “resistant starch” (less digestible), digestion and absorption are slower.
Formulation benefits and cautions
Because they are low GI and high in fiber, they may help support blood glucose control and improve stool quality. Studies report that lentil-based diets showed little to no postprandial blood glucose rise.
However, legumes may contain anti-nutritional factors (a general term for compounds that can interfere with nutrient metabolism or absorption), so formulas that replace carbohydrates predominantly with legumes should be evaluated carefully for potential reductions in digestibility.
As this analysis shows, each carbohydrate ingredient has both strengths and limitations, and no single ingredient is “universally superior.” Developers must understand these properties deeply and combine them strategically according to the product concept and the target cat’s health status. In the next section, we provide formulation design guidelines based on these insights.
Technical guidelines for formulation design
Below are practical formulation design guidelines that integrate the analysis above and can be applied directly to product development. Developers must continuously link three perspectives—feline physiology, ingredient properties, and manufacturing technology—when building an optimal formula.
Setting total carbohydrate level
Carbohydrate content must be determined within the overall nutritional balance of the product.
- Typical formulation:
In general adult maintenance complete-and-balanced dry foods, total carbohydrate content is commonly designed around 30–35%. - Specific objectives:
For therapeutic diets aimed at managing diabetes or obesity, or for senior cat formulas, carbohydrate levels may be reduced to 20% or lower.
Determining carbohydrate level is not simply a matter of setting inclusion rates; it is also a strategic decision to manage nutritional and cost trade-offs among protein, fat, and carbohydrates.
Managing degree of gelatinization and target values
To ensure carbohydrate digestibility and safety, controlling gelatinization in manufacturing is a top priority.
- Target:
Aim for a degree of gelatinization of 90% or higher during extrusion. - Impact on quality:
High gelatinization is directly linked to improved digestibility, better palatability, and favorable stool quality. Conversely, low gelatinization increases the risk of indigestion and abnormal fermentation in the gut. This requires optimizing manufacturing conditions (temperature, pressure, moisture, residence time, etc.) and building the technical capability to consistently achieve high gelatinization.
Balancing ingredient combinations
Relying on a single carbohydrate source increases risk. Instead, strategically combine multiple ingredients with different characteristics to optimize the nutritional profile.
- Managing glycemic response:
For example, when using high-GI potato, combining it with low-GI, fiber-rich legumes can help mitigate rapid postprandial blood glucose rises. - Managing stool quality
In addition to the starch source that forms kibble structure, it is common to add small amounts of functional fiber sources such as cellulose (insoluble fiber) or beet pulp to adjust stool firmness and volume.
Integration with the manufacturing process
Manufacturing conditions are inseparable from formulation design.
- Leveraging high-STE processing:
Higher thermal energy (high STE) can improve kibble expansion and gelatinization and may increase palatability. - Quality control trade-offs:
Excessive heat can also destroy heat-sensitive nutrients such as certain vitamins. Formulators must work closely with manufacturing teams to identify optimal processing conditions that maximize ingredient performance while minimizing nutrient losses.
These guidelines form the foundation for developing high-quality cat food that is safe, highly digestible, and supportive of feline health. Building on this foundation by incorporating consumer needs and the latest research trends leads to more competitive product development.
Latest market trends and research directions
As pet owners’ health awareness rises and nutrition research advances, cat food product development is shifting toward new directions. The industry is moving beyond basic nutritional adequacy toward higher-value products that address specific health issues or more closely reflect a “natural” diet concept.
Key recent trends and research directions in cat food include the following.
High-protein, low-carbohydrate
To address modern feline health issues such as obesity and diabetes, low-carbohydrate, high-protein (LCHP) diets are attracting attention. This approach aligns more closely with cats’ carnivorous physiology, and an increasing number of studies report that LCHP diets can support weight loss and improve glycemic control in cats.
Growth of grain-free products
Driven by concerns about grain allergies and the belief that “cats don’t need grains,” grain-free products have gained strong market presence. These products typically use peas, potatoes, and tapioca as primary carbohydrate sources.
As a result, compared with conventional grain-based foods, these diets often trend toward lower GI profiles, and may contribute to obesity prevention or reduced diabetes risk—though outcomes depend on overall formulation and processing.
Focus on gut health
With increasing recognition of the importance of the gut microbiome in overall health, there is a growing trend to include ingredients that support intestinal health. Specifically, more products actively add prebiotics (indigestible oligosaccharides, inulin, etc.) that serve as substrates for beneficial bacteria.
Research on functional carbohydrates
To suppress rapid rises in blood glucose, research is progressing on new carbohydrate ingredients with very slow digestion and absorption profiles. For example, functional sugars such as isomaltulose are being studied as sustained energy sources, and their potential applications in pet food are gaining attention.
These trends show that the industry is shifting toward valuing the “quality” and “functionality” of carbohydrates—rather than viewing them only as energy sources or structural agents. Going forward, it will be increasingly important to accurately capture these developments and design products based on scientific evidence.