Cat Food and Hydration

Why Is It Difficult for Cats to Digest Carbohydrates?

The use of carbs in cat food is controversial. While some people see them as a good source of energy, others believe that carbohydrates are responsible for the rise in feline obesity and diabetes. Nevertheless, both sides would agree that cats digest carbohydrates less efficiently than other animals.

Cats evolved on a carnivorous (meat-based) diet, so most of their digestive enzymes are geared towards digesting protein rather than carbohydrates. Nevertheless, cats can tolerate some forms of carbohydrate better than others. To be specific, most cats can digest cooked starches, but not sucrose.

Although you should avoid high-carbohydrate cat foods, you shouldn’t try to eliminate carbs from your cat’s diet altogether. Carbohydrates may have some health benefits, and even wild cats consume them in small amounts. So, if you want to monitor/reduce your cat’s intake of carbohydrates, this guide will show you how to do so safely.

Issues with Feeding Cats Carbs

To understand why there’s so much controversy surrounding this issue, here are some of the problems with feeding your cat carbohydrates.

Reduces Protein Consumption

Carbohydrates are often used to ‘bulk out’ cat foods, particularly kibbles. Although legislation is in place to ensure the protein content of cat food doesn’t fall below 25%, domestic cats still consume quite a lot less protein (and relatively more carbohydrates) than cats living in the wild.

Some research suggests that a high-carb diet may even interfere with the absorption of protein.

Diarrhea, Vomiting, Bloating, and Flatulence

Certain types of carbohydrates are almost impossible for a cat to digest. Other types of carbohydrates are easier on the cat’s stomach, but they still might cause mild symptoms, such as flatulence and bloating.

Cause of Diabetes Mellitus

Carb-rich cat food has been blamed for the rise in feline diabetes.

May Lead to Obesity

Domestic cats certainly do eat more carbohydrates than wild cats. This is compounded by the fact that many domestic cats are very inactive, so they don’t burn off the excess calories.

According to AAFCO, cat food is allowed to contain up to 55% carbohydrates. If carbs are responsible for the above health problems, it’s easy to see why pet owners would be worried about feeding their cats conventional cat food.

Do Cats Need Carbohydrates in Their Diet?

Given the problems associated with carbohydrates, you might wonder if they hold any nutritional value for cats.

Well, according to nutritional guidelines, there are no minimum carbohydrate requirements for cats. Cats have evolved on a high-protein diet, so they’ve learned to create energy from the amino acids in animal flesh.

Cats living in the wild do consume small amounts of carbohydrates. For example, cats eat insects and small amounts of vegetation.

Also, their prey (i.e., mice and rats) would have a small amount of carbohydrate in their stomachs. Prey animals typically contain between 1 and 8% carbohydrate, so even the wildest of cats will consume a small amount of carbohydrate.

According to the Pet Food Manufacturing Association, carbs can aid digestion if they are added to pet food responsibly. For example, certain complex carbohydrates are high in fiber (beet pulp) and can help keep the cat’s digestive system running smoothly.

Moreover, when a cat is pregnant, they seem to benefit from a relatively high-carbohydrate diet as protein cannot be absorbed as efficiently.

So, while cats don’t generally ‘need’ carbohydrates to thrive (especially in comparison to dogs or humans), it is natural for them to consume small amounts of carbohydrates. As such, it would be inappropriate to try and eliminate this macronutrient completely.

can cats metabolize sugar?

Can Cats Digest Carbohydrates?

It’s too simplistic to say that cats can’t digest carbohydrates. It is more accurate to say that cats digest carbohydrates less efficiently than other animals. This is because they only have small amounts of the digestive enzymes required for digesting carbs. For example:

  • Cats have low levels of amylase in their pancreas – amylase helps to break down carbs.
  • A cat’s pancreatic tissue has low maltase activity – maltase helps to break down maltose into glucose (sugar).
  • There is no (or very little) lactase or sucrase activity in the pancreatic tissue – lactase is the enzyme required to process lactose (found in cow’s milk), and sucrase is the enzyme that processes sucrose.
  • Maltase, Isomaltose, and sucrase enzymes are present in the small intestine, but activity is low.

As you can see, cats are not incapable of digesting carbohydrates, but they’re not particularly efficient at doing so. At least two factors determine how efficiently the cat will be able to digest carbohydrates. These factors include:  

  • The type of carbohydrate
  • The portion size

Which Carbohydrates Are Bad for Cats?

There are many different types of carbohydrates, and some are very difficult for cats to digest. For example, there is strong evidence to suggest that cats cannot tolerate sucrose.

Sucrose is broken down by the enzyme sucrase. Cats do have sucrase enzymes in their small intestine, but the activity is very low. This means they will struggle to break down sucrose. Some cats respond badly to minuscule amounts of sucrose whereas other cats can tolerate slightly larger amounts.

Research shows that if cats consume more than 7g of glucose per kg of body weight (or if more than 36% of the meal contains sucrose), the side effects are likely to be significant. These side effects include bloating, flatulence, lethargy, and diarrhea (potentially leading to dehydration).

Thankfully, sucrose is generally not added to cat food (at least not in any significant amount). The type of carbohydrate used in conventional cat food is easier for cats to digest.

Cats do occasionally overeat sucrose. This can happen if they get their paws on leftovers or sweet treats, such as:

Best Carbohydrates for Cats to Digest

Most cats can tolerate starches (polysaccharides) pretty well. Starches are complex carbohydrates so they may be digested in a different way to simple sugars.   According to NCBI, the following starches (cooked) are digested very well in cats:

  • Cassava flour
  • Brewer’s rice
  • Corn
  • Sorghum
  • Pea
  • Lentil

The brewer’s rice was digested most effectively, but the digestibility was above 93% for all of the above starches. Indeed, most of the carbohydrate added to conventional cat food is starch.

In the above study, starch accounted for 35% of the cat’s entire meal. To promote a healthy, balanced diet, the starch must be balanced with other macronutrients such as protein and fat.

Why is it difficult for cats to digest carbohydrates?

How Much Carbohydrate Can Cats Digest?

Most cats can digest starches, as long as they are consumed in moderation. If too much carbohydrate is consumed, it may pass through the small intestine (undigested) and into the colon – where it will ferment.

If carbs are left to ferment in the colon, this will alter the microbial environment and may lead to symptoms such as:

  • Diarrhea
  • Flatulence
  • Bloating
  • Bacterial overgrowth leading to more severe illness

So how much carbohydrate is tolerable for a cat? There’s no clear consensus on this topic. In the US, the Association of American Feed Control Officials requires the carbohydrate content of cat food to be no more than 55% (there also must be a minimum of 25% protein and 20% fat).

If you shop around, you’ll see that some cat foods do contain quite a lot less than 55% carbohydrate. Research suggests that a better range would probably be between 15% and 35% carbs.

This would better mimic a cat’s natural diet, while still allowing manufacturers and pet owners to benefit from the economic and practical aspects of using carbs in cat food.  

So, if you’re concerned about the risks associated with a high-carb diet, try to purchase cat food that contains a lot less than 55% carbohydrates. 

How to Check the Carb Content of Cat Food

Unfortunately, pet food manufacturers rarely list the carbohydrate content of their products. It is a legal requirement for pet food manufacturers to declare the following information:

  • % Crude Protein (minimum)
  • % Crude Fat (minimum)
  • % Crude Fiber (maximum)
  • % Moisture (maximum)

A measure for ash is usually also provided (though it is not a requirement). If it is not provided, you can estimate it as 3%. If you add up the above percentages and subtract from 100, the result gives you a very rough estimate of the carb content of your cat’s food.

You cannot compare the carbohydrate content of wet food with dry food using this calculation – due to the differences in moisture content. Nevertheless, it’s true to say that dry food almost always has a higher carb-content than wet food.

The average kibble contains around 30-40% starch, whereas the average wet food contains 1-7% starch. This is because more starches are required in the production of kibble.

A small amount of carbohydrate is used in the production of wet food, for example: to thicken the gravy, add a caramel color, or ‘set’ the food into a loaf shape, but much more is required when producing kibble.

If you’re concerned about the carb-content of your cat’s meals, perhaps the easiest thing to do would be to cut down on kibble.

Does Grazing Help Cats Digest Carbs?

Cats can digest cooked starches quite well, despite the fact that they’ve evolved on a meat-based diet. Some scientists believe this is because cats eat little and often.

Cats only have small amounts of digestive enzymes such as amylase, but if their portion sizes are very small, this doesn’t matter too much.

When given a choice, cats eat little and often throughout the day – giving their body time to digest a meal. This may explain how they’ve adapted their digestive system to a higher-carb diet.

So, if you allow your cat to graze on 4-8 very small meals per day (rather than one or two larger ones) they may be able to digest and metabolize carbohydrates more comfortably.  It’s important to say that ‘grazing’ can lead to obesity if it is not done sensibly.

Is My Cat Allergic to Carbohydrates?

Although most cats can digest starches (cooked), a small number may be intolerant or allergic to certain cereals, grains, or vegetables. Symptoms of an allergic reaction include:

  • Vomiting
  • Diarrhea
  • Inflamed or itchy skin
  • Runny eyes
  • Wheezing / difficulty breathing

Switching to a hypoallergic cat food often helps as these foods do not include common carbohydrate allergens (such as corn).

In some cases, food allergies are to blame for Inflammatory Bowel Disease (IBD). If a new, more appropriate diet is found, this can clear up the IBD. Nevertheless, IBD can be caused by many different factors, so changing a cat’s diet does not always help.

Do Carbohydrates Cause Diabetes in Cats?

Diabetes mellitus is one of the most common metabolic disorders in cats. Some scientists believe that carbohydrates are directly responsible for causing diabetes in cats. 

According to this theory – carbohydrates spike the cat’s blood sugar, and the cat takes a long time to clear sugar from the blood (because cats lack the hepatic enzymes required to process glucose effectively).

This puts a lot of pressure on the pancreas to keep producing enough insulin to cope with high levels of sugar in the blood. Over time, this leads to insulin resistance, and type 2 diabetes.

However, it should be said that this is a hypothesis, and there are very few clinical studies to support this theory. Most vets and specialists agree that there is not enough evidence to show that eating carbohydrates causes diabetes in cats.

Nevertheless, it is widely accepted that high-carbohydrate foods may play an indirect role in causing diabetes because eating carb-rich foods can lead to obesity (a significant risk factor for diabetes). Additional risk factors for diabetes include:

  • Age – 10+ years
  • Sex – male cats are more at risk
  • De-sexed cats – cats who are neutered/spayed are slightly more at risk
  • Corticosteroid/ Progestins
  • Inactivity/ confinement
  • Genetic – a potential predisposition in Burmese cats

Whil2 there is no clear evidence to suggest that carbohydrates directly cause diabetes, a low-carb diet may help manage diabetes because it should help with weight management.

best carbohydrates for cats

Do Carbohydrates Cause Obesity in Cats?

Feline obesity is a real problem, and it is on the rise according to many vets. It seems likely that carb-rich kibble cat foods are partially to blame. However, other factors may also play a role. For example:

  • Fat Content – The relatively high-fat content of some cat foods (sometimes up to 45%).
  • Palatability – The palatability of foods has improved in recent years – making cats more likely to overeat.
  • Grazing – Allowing a pet to graze on food throughout the day is generally a good thing because it recreates their natural feeding behavior. However, if you don’t closely monitor the amount of food you’re making available, your cat might start overeating.
  • Inactivity – This is perhaps the leading cause of obesity in cats. A cat in the wild would catch up to 9 small meals in 24 hours, but they’d burn a lot of calories while hunting for these meals. Cats who spend all their time indoors will eat a similar number of calories – but burn off very few in comparison (especially if they are not encouraged to play).

While cutting down on carbohydrate-rich foods may help to prevent feline obesity, it’s also important to consider how often you’re feeding your cat, and whether you’re meeting their physical and emotional needs.

Are Alternative Cat Foods Better?

If conventional cat foods contain up to 55% carbohydrate, might it be better to consider alternative cat foods? In recent years, the trend for raw, organic and meat-based cat foods has grown.

These alternative cat foods contain only very small amounts of vegetables or cereals. The problem is, they can cost 4 or 5 times the price per portion. So, are alternative cat foods better for your cat?  

There has been no long-term, large scale studies to test the benefits of raw, meat-based diets for domestic cats. Common sense tells us that these diets probably are quite beneficial, especially for weight management.

However, it’s important to note that feeding your cat a raw food diet might increase their risk of contracting a bacterial infection.

If you want to control the number of carbs your cat consumes – but you don’t want the expense of an ‘alternative’ cat food – there are some other ways you can reduce carbs in their diet. Let’s finish by summarizing these tips.

How to Manage Carbohydrates in a Cat’s Diet

Carbohydrates are not ‘toxic’ for cats, but they should be consumed in moderation. To ensure your cat is consuming a healthy amount of carbs, consider the following tips:

Check Labels

Although there is no legal requirement to print the carbohydrate content on cat food labels, you can work out a rough estimate using the calculation mentioned in this article. For kibble, try to select a product that contains less than 30% carbohydrate and certainly less than 40%.

Wet Food

If your cat eats a lot of dry food, try substituting some of it for wet food, as wet food generally contains less starch.

If you increase wet food and decrease kibble, make sure you are feeding them the correct number of calories over the course of the day. An overweight domestic cat requires around 240 kcals a day, and a lean cat requires around 280 kcals.

Do Not Feed Leftovers

Do not give your cat leftovers or ‘treats’ as these may contain sucrose (which is highly indigestible for cats). This includes the obvious sweet treats like cakes and cookies, but also pasta/meat sauces.


Cat foods containing fibrous starch (such as beet pulp) can be very beneficial for your cat’s digestive system.


If you’re caring for a pregnant cat, they’ll need to consume a lot more calories per day (up to 800 kcal). Feeding them a cat food that’s relatively high in carbs (i.e., 30-45%) may be a good way of satisfying their energy requirements.

Also, as mentioned, there is some evidence to suggest that carbs may be particularly beneficial for cats during pregnancy.

Carbohydrate Allergies

If your cat has chronic bloating, diarrhea and/or vomiting after eating conventional cat food, they may have an intolerance or allergy to one of the ingredients.

Cats are more likely to have an allergy to carbohydrates than meats. If you see these symptoms, take your cat to the vet for an examination. Your vet may recommend a hypoallergenic cat food.

Consider Alternative Cat Food

If you have the budget for it, you could consider feeding your cat a raw/organic meat-based diet. These diets mimic, as closely as possible, the diet your cat would eat in the wild.

There are no long-term studies to back up the efficacy of these diets but, intuitively, they seem to be a good idea.

Allow Your Cat to Graze

As mentioned, cats can digest starches more effectively if they consume them in small amounts. If possible, try to feed your cat 4 – 8 small meals per day (instead of one or two).

However, only put one small portion down at a time. If you are out of the house for most of the day, consider buying a cat food dispenser. As mentioned, keep a tally of the total calorie content of all the ‘meals’ to ensure you are not overfeeding your pet.

Although carbohydrates can be somewhat difficult to digest, they still have a small place in the cat’s diet; even wild cats consume them.

Though carbohydrates have been linked to conditions such as obesity and diabetes, other factors play a role in these conditions, such as overfeeding and physical inactivity.

If you want to improve your cat’s health, it’s important to attend to their overall needs. This includes playing with them regularly, feeding them appropriate portion sizes, and keeping a close eye on their carbohydrate consumption.