Fibre is a carbohydrate found naturally in plants, and is an important nutrient for gut health. It helps maintain healthy stools (poo!), and can also be useful for both losing weight, and for keeping the weight off. Dietary fibre has also been shown to affect the gut microbiome, which is important for so many aspects of overall health. 

So, we all know how important dietary fibre is for people, but let’s take a look at the question, “is fibre important for cats?”

What is fibre?

Well, that’s a surprisingly tricky one to answer! Fibre is given many, often confusing, definitions. Essentially, fibre is in the macronutrient class carbohydrates, and is found naturally in plants. However, it’s different from other carbohydrates, such as starches and sugars, because it is resistant to digestion by enzymes in the small intestine. Examples of fibre sources that you may see as pet food ingredients include cellulose, gums and pectin. 

Fibre can be classified in a number of ways, one of which being its fermentability. Fermentability describes the amount of fermentation by microbes in the colon. This process produces short chain fatty acids (SCFAs), which the cells in the colon use for energy. Rapidly (sometimes known as highly) fermentable fibres produce more SCFAs than those which ferment slowly. 

When talking about pet food, it’s often more helpful to classify fibre as soluble or insoluble. 

Soluble fibre

Soluble fibres, such as pectins or gums, tend to slow down the movement of food through the gut. Soluble fibres tend to be highly fermentable, meaning they produce more SCFAs, which provide energy to the cells of the colon. SCFAs may also be important in keeping blood glucose levels stable.

Insoluble fibre

Insoluble fibre, such as cellulose, has a bulking effect on stools. These aren’t just cheap fillers, as commonly misconstrued, and they play an important role in the gut too.

Now that we understand what fibre is, let’s take a look at whether fibre is important for cats.

What is the function of fibre in cat food?

With so much information available on the internet, it can be very hard to decide what to believe. For example, some sites claim that fibre in a pet food is just a ‘cheap filler’. The World Small Animal Veterinary Association (WSAVA) has published this handy guide to nutrition on the internet, which can help you decide which sources are trustworthy. 

So, do cats need fibre? Cats are obligate carnivores, meaning they must have certain amino acids (the building blocks of protein) in their diet, which are only found in meat. So, while the mainstay of their diet should be protein from meat sources, cats can still digest plant material. If we liken this to the ‘wild’, cats would have eaten prey whole, which would have included the contents of the herbivore’s stomach. 

Most cat foods contain a ‘moderate’ amount of fibre, which helps to keep a healthy stool volume and to provide energy for a healthy colon. More recent research indicates that soluble fibre also acts as a prebiotic, enriching the gut’s microbiome. This could help to promote a healthy digestive and immune system.

Fibre also has a role to play in certain medical conditions, where a high fibre diet may be recommended. These include:

Obesity

Obesity is a growing problem in cats in the United Kingdom, and around the world. Being overweight increases a cat’s risk of many health issues, including diabetes and joint disease. 

High fibre diets have been proven to help with weight loss in cats. They tend to make a cat feel fuller than regular cat food. This is partly because the increased fibre causes the food to stay in the stomach longer (known as ‘delayed gastric emptying’). It also ‘bulks’ the food in the stomach. Both of these lead to the cat feeling that they are full, meaning they eat less food. Fibre is also lower in calories per gram than other nutrients, which also helps with weight loss. 

Diarrhoea and constipation

Dietary fibre helps to normalise the water content in the stool, which is why it can be helpful for both diarrhoea and constipation. It can also help with diarrhoea by increasing the time the material spends in the gut, giving more time for water to be absorbed from the stool back into the body. 

Increased soluble fibre, such as psyllium, can be helpful for constipation in cats, especially in chronic cases. The soluble fibre absorbs water, increasing the volume of the stool and making them softer and easier to pass. Naturally, increased water intake is just as important, or this won’t help! It’s important to note that increased fibre is not recommended in cats with very severe constipation, so it’s safest to check with your vet before making any dietary changes.

Hairballs

Some studies have shown that high fibre diets may help ingested fur to pass through the gut, so reducing the number of hairballs brought up. 

Diabetes Mellitus

High fibre diets used to be recommended for cats with diabetes. However, it is now thought that high protein, low carbohydrate diets are ideal, as they have been shown to improve glucose control. While high fibre diets are generally not recommended for healthy weight or underweight cats with diabetes anymore, they can still play an important role in weight loss for overweight or obese cats with diabetes. If your cat is diabetic, ask your vet or vet nurse for advice on the best diet for their individual needs.

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If your cat has a medical condition or complaint which you think may benefit from a diet change, you should always seek advice from your vet before changing anything. As you can see, there are different types of fibre which can be present in varying amounts. The amount and type of fibre that your cat needs will depend on their individual and unique needs.

Cat food labels 

Reading cat food labels can be very confusing, even for professionals! Labels on pet foods must declare the ‘crude fibre’ content, which is mostly insoluble fibres. The total fibre content (i.e. soluble and insoluble) is rarely shown, so the label can be misleading. If you want to compare fibre between diets, it’s more reliable to ask the companies for the total dietary fibre (on an energy basis) so that you can make a comparison.

The World Small Animal Veterinary Association (WSAVA) has produced a useful guide for choosing a pet food, including what to look for on a label.

Side effects of fibre

As with anything, while fibre can have some great benefits, there are some potential side effects. If your cat doesn’t need to lose weight, a high-fibre diet may contribute to unwanted weight loss, since it’s low in calories. It could also lead to excess gas and a higher volume of stool. High fibre content can reduce the palatability (tastiness!) of the food too.

If you are changing your cat’s diet, you should do so slowly, over 1 – 2 weeks. This can help to minimise unwanted side effects and gives your cat time to adjust to the new food. 

You should always ask your vet or vet nurse for advice before changing your cat’s diet if they have any medical conditions.