Grain-free Cat Food: Good or Bad?

Pet parents are spending more time researching what is best for their pets, and there is (quite rightly) a greater emphasis on preventative health care nowadays. One of the major hypes in the pet food industry is grain-free food. But is that what it is, just another hype.. or is grain-free pet food actually a healthy choice? We asked vet Sarah for her opinion:

The theory behind grain-free diets is that cats are carnivores and can’t easily digest grains like corn, wheat, corn, barley, and oats. Supposedly, these grains can damage the gastrointestinal tract and contribute to food allergies or intolerances. But is there actually any truth behind these theories?

Benefits of grain-free cat food

We will now briefly consider some possible reasons why grain-free cat food is on the market:


While grain-free food has become more of a hype in recent years, the real reason that these foods came into existence was that some cats were found to be allergic to certain grains. However, contrary to what manufacturers would have you believe, this is a rather rare occurrence1. Studies show that grains are some of the least likely causes of allergic reactions in felines.

A good source of protein

Protein is the most important ingredient in cat food because, unlike most animals, they are a cat’s primary energy source. A lot of people falsely believe that these proteins always need to come from animals, but this is only partly true. The reason animal-sourced proteins are so significant is that they contain the essential amino acid taurine, which is not found in other proteins. This is why every cat food should at least contain some form of meat.

However, the assumption that cats can’t get protein from other types of food like grains is completely false. In fact, cats are very good at digesting plant-based ingredients. These can be a great source of not only protein but also fats and carbohydrates.

Disadvantages of grain-free cat food

There is a common belief that grain is added to cat food as a cheap filler material. This is a misconception. Read this article by scientists over at Royal Canin, which explains that cats can perfectly digest grains, and they can be a great source of fiber, vitamins, minerals, and essential fatty acids.

A serious problem with many grain-free diets is that they are cutting out some essential nutrients (or in some cases contain too much of them) without good cause. Not all grains contain gluten, so even if your cat cannot tolerate gluten (which is pretty rare by itself), they may still not necessarily need to be put on a diet that contains no grains at all.

Phosphor and Kidney Disease

When grains are removed from a diet, more meat is often used to replace that volume. A big problem with diets high in meat is that they typically contain too much phosphorus. While phosphorus is an essential nutrient in the right amounts, there is a link between high-phosphorus foods and a faster progression of kidney disease in cats. Grains, on the other hand, can provide a bit of protein being very low on phosphorus.

The higher amount of fat might also negatively affect CKD progression. Here’s what RoyalCanin had to say on the subject:

a diet that is low in total carbohydrates must inherently be higher in protein and fat, which may be an inappropriate profile for animals with some medical conditions, including chronic kidney disease and those requiring dietary fat reduction


Although carnivores, cats are able to digest and obtain nutrients from grains, albeit to a lesser extent than dogs. The carbohydrates that are substituted in place of grains are often lower in fiber and higher in calories. Leading to the common question “does grain-free cat food cause constipation”? Indeed, it can contribute to gastrointestinal problems. Fiber is important for passing stools and preventing hairballs.

Comparisons to normal food

We looked at a recently published study that compared the carbohydrate content of several grain-free foods versus normal foods. These were some of the conclusions:

  • The average calories across both categories were similar
  • The average amount of carbohydrates was significantly lower in grain-free food
  • The most common plant-sourced ingredients in grain-free foods were peas, cranberries, potato and carrot.
  • Grain-free food products were more likely to contain exotic meats such as rabbit and bison meat.

Grain-free food reviews

When looking at reviews in order to choose a grain-free cat food there are several things to consider. The nutritional value, rather than the ingredients, is the single most important thing to review (unless your cat has been diagnosed in a rare case of food intolerance).

A good food grain-free food can be recognized by the amount of fiber is present, whether the calorie content is low enough, and if the phosphorous levels are now too high. The most important nutrients found in grains are taurine, iron, thiamine, calcium, riboflavin, folate and niacin; ideally, the review should discuss these.


From a scientific point of view, food allergies are currently the only valid reason to put your cat on a grain-free diet

So, is grain-free cat food better than regular foods? Some grain-free cat foods are lower in carbohydrates and higher in protein than regular foods. This is of benefit since cats are obligate carnivores and protein is their primary energy source.

High-carbohydrate diets predispose cats to diabetes and obesity, so should generally be avoided. However, grain-free does not always mean low carbohydrates. Some grain-less cat foods substitute grains for other carbohydrate sources; such as potato, sweet potato or tapioca.

So why should I choose grain-free food for my cat?

There is currently no published evidence to support claims that cat food without grains will improve cat health. There are some anecdotal reports of cats getting improved skin and digestive health. As long as the grain-free diet is complete and balanced, then there is no harm in trialing one, to see if it suits your kitty. Just be sure to choose a complete one, designed to complement the nutritional needs of your cat at its current age.

The only real evidence-based advantages of diets without grains are better skin management and preventing gastrointestinal disease that is caused by an adverse food reaction; or for elimination diets to determine what foods a cat may be intolerant to. Elimination diets should only be performed under the guidance of a veterinary surgeon.

Some studies have suggested that grains can cause alkaline urine, which harms the urinary tract. However, this depends on the number of grains and is again not yet scientifically proven.

Final words on grain-free food

In a saturated market, pet food manufacturers are trying everything to sell their products and it seems grain-free is one of the latest trends used purely for marketing purposes. Aside from rare cases where pets are intolerant to grains, there is little to no scientific evidence to support these claims that grain-free diets are healthier than their normal counterparts.

In fact, the majority of cats are very efficient at digesting grains, and whole grains contribute valuable nutrients including vitamins, minerals, essential fatty acids, and fiber to a diet.

Frequently Asked Questions

Is grain-free good for cats with sensitive stomachs?

Anecdotally, yes. Scientifically, only if your cat has a grain allergy or intolerance, which is more uncommon than some sources would have you believe.

What is the relationship between grain-free cat food and heart disease?

There have been reports of health problems in animals on low-grain diets, most importantly a heart disease called Dilated Cardiomyopathy (DCM) in dogs. The exact cause remains unclear and studies are underway. The same problems have not been found with cat food, but it’s essential that any food contains enough taurine to prevent heart disease in cats.

Is there a difference between grain-free wet and dry food?

Any dry food tends to be higher in carbohydrate and in plant-based protein than wet food, as well as being lower in water content. Cats have inherited a naturally low thirst drive from their desert-dwelling ancestors, so food can be an important source of water.

Does it matter which brand of grain-free cat food I go with?

Definitely! Choose one that is balanced and complete with high-quality ingredients. Ideally, choose a brand from a big company that employs a nutritionist rather than a ‘boutique’ brand.

Leave a Reply

Your email address will not be published. Required fields are marked *