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 world is grain-free food.

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 has become a hype in recent years, the real reason these foods excist is because cats can be allergic to grains like we can. But contrary to the general consensus, this is a rather rare occurence: studies have found that grains are one of the least likely sources of food allergy.

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 important is because they contain the essential amino acid taurine, which is not found in other proteins. This is why every food should 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.

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

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 often 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 beeing 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 a rare case of food intolerance).

A good food grain-free food can be recognised 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.


So, is grain-free cat food better than regular foods? Some grain-free cat foods are lower in carbohydrate 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 carbohydrate. 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 it’s 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 quantity of grains and is again not yet scienftifically 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 for 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.

In short, don’t buy into the grain-free hype. The only thing these foods do that regular foods don’t, is quickly empty your wallet.

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