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Understanding 8 Main Nutrients in Cat Food

Understanding 8 Main Nutrients in Cat Food

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There are six main ingredients in every diet, cat and human alike. These include protein, carbohydrates, fats, vitamins, minerals, and water. Let’s explore each individual ingredient.

1. Protein: The Most Important Ingredient

Protein is made up of smaller components called amino acids. There are essential and non-essential amino acids. The essential amino acids cannot be made by the cat’s body and must be found in its diet. Others are considered non-essential because the cat can make its own from building blocks in the diet.

What is a protein source and why does the body need it?

Protein comes from a variety of sources. There are animal- based proteins and plant-based protein sources. Examples of animal-based protein include chicken, turkey, and fish. Examples of plant-based protein sources are corn and soy.

The body uses dietary protein to produce hair, nails, tendons, cartilage, connective tissue, cells, enzymes, hormones, antibodies, DNA, and many other things.

Does it matter if the protein in the diet comes from animal-based or plant-based sources?

Plant-based proteins (vegetable proteins) are harder for cats to digest and are often times lacking in certain essential amino acids. Some cats cannot digest plant-based proteins at all.

Pet food companies will often use plant-based proteins because these are more readily available, cheaper, and easier to handle and store. But they are not good for your cat’s health.

Is there a difference in quality of the proteins used in commercial pet foods?


What is a quality protein?

A quality protein source for a cat is human-grade organ and muscle meat. This is a quality protein source for three reasons: it is the right type (animal-based) protein, it is digestible, and it comes from the human food chain.

There are the three factors in a quality protein source:

Type or source of protein

There are two sources, or two types, of protein. One is protein from animals and the other is protein from plants. In a cat’s natural diet, it eats eat prey, not plants. So, we want to choose a food that will feed our cats meat and not plants. They are carnivores (meat-eaters).

Examples: Chicken, beef, lamb, turkey, venison, bison, duck, rabbit and chicken meal.


Not only is the type of protein (animal or vegetable) you choose to feed your cat important, the digestibility of that protein is important as well.

Animal protein sources are a part of a cat’s natural diet. Its body knows how to break down the muscle and organ meats of its prey into amino acids, the building blocks for a healthy body. Animal protein is a digestible source of protein, and the body breaks it down very effectively and efficiently.

What is an example of an indigestible animal protein source?

That would be something that is made up of amino acids but is hard for the body to break down into the individual amino acid building blocks. For example, fur. Fur is made of protein (strings of amino acids) but if your cat eats fur, it would have a hard time digesting it. The fur would simply pass into the stool undigested. Other examples would include nails, hide, beaks, and feathers.

How can I tell how digestible the commercial pet food product is?

That is the catch. This information is NOT provided to us by the pet food manufacturer. It is not generally not listed anywhere on the bag or can of food. The only “best-guess method” to determine digestibility is to try feeding the diet and watch for stool volume and consistency. Indigestible portions of the diet result in larger stool formation. If your pet has frequent stools with large volume, the food is not high quality.

What is Human-Grade Food?

Human-grade food means that it has passed inspection for human consumption. So what happens to food that doesn’t pass inspection? It ends up in containers marked “pet-grade” food and is fed to our pets in commercial products.

Read that sentence again and let it all sink in. One more time, read it again, stop, and think about that.

Conclusions on Proteins

Cats are designed to handle a high-protein diet. If there is not enough digestible protein in the diet, your cat will start to break down its own muscle tissue to make energy. It is important for cats to have animal-based sources of protein, which are highly digestible. High-protein diets that consist of poor quality, indigestible ingredients are detrimental to the kidney function. High-protein diets should consist of quality, human-grade animal sources.

Two cats are eating beef steak.
Cats are eating raw red meat.

2. Carbohydrates

Carbohydrates are sugars. There are complex carbohydrates and simple carbohydrates, but the bottom line is that they all break down into sugar (glucose).

What is a carbohydrate source and what are carbohydrates used for?

Carbohydrates are plants. Sources include grains and grain products, fruits, and vegetables.

Carbohydrates are broken down into sugar (glucose) and are used to feed the cells, especially the brain cells. Excess glucose is stored as fat for later use. Every cell in the body requires glucose. However, cats are better at making emergency-use glucose from proteins, not carbohydrate sources.

Does it matter whether the carbohydrate sources come from grains, fruits ,or vegetables?


Grains are not a natural part of your cat’s diet. These are complex carbohydrates. Dr. Greco says that it can actually take a cat six hours to digest a complex carbohydrate. Remember that the cat’s GI tract is short and there is not a lot of time to do difficult digestive processes like this.

Fruits and vegetables are good healthy sources of carbohydrates and are fine, in small amounts. Be sure they are quality sources.

Is there a difference in quality of the carbohydrates used in commercial pet foods?


Many commercial pet food companies choose grains as their carbohydrate source. We have just learned that this is not a good idea. On top of that, they don’t typically use the best quality grains, just leftovers that couldn’t be used anywhere in the human food chain. So, the poor kitties get a double whammy here, too! Not only are grains being used, but poor-quality ones at that!

Just as with proteins, a poor choice in carbohydrate sources decreases digestibility. Lots of complex carbohydrate sources in the diet will result in larger volumes of stool due to their indigestible nature. This means you get to clean out the litter box more often. Also, large amounts of carbohydrates (digestible or non-digestible) will result in too large a stool volume, resulting in constipation.

Conclusions on Carbohydrates

Cats need carbohydrates in their diet. These should come from quality sources like vegetables and fruits. A wild cat will supplement its diet with vegetation on occasion. For example, a lion will go right for the stomach contents of its prey and feast on the fermenting vegetation there. However, carbs still make up a small portion of the lion’s overall meal. In addition, the prey’s stomach contents include enzymes, which help the lion to digest those carbohydrates.

I gave strawberry to my cats.
Cats and strawberries

3. Fiber

Fiber is the most complex of carbohydrates and is oftentimes not digestible.

There is virtually no fiber in a cat’s natural diet of prey. Yet, fiber content is quite high in many commercial generic foods. High fiber can decrease absorption of some proteins, carbs, vitamins, and minerals. A high-fiber diet produces a larger volume stool. As cats age, however, fiber may need to be supplemented in some disease processes.

4. Fats

Fats are a major source of energy. Also, fats help keep your cat’s skin healthy and shiny. Just as with the proteins, there are essential fats and non-essential fats. Dogs benefit from a 5:1 ratio of Omega 6 (linoleic acid) to Omega 3 (linolenic acid) fatty acids. This ratio is unclear in cats.

Too little fat is not good. Fat signals the brain that the body is full and can stop eating now. Overeating occurs when this signal isn’t given. Adding an appropriate amount of fat to the feline diet does increase production costs, so many foods are low fat. Low-fat diets don’t satiate the cat, so it wants more food, which will lead to obesity issues.

Fats are also required in the diet to help the animal absorb fat-soluble vitamins. Fat also helps to improve the taste of the food product.

Feeding a diet that is labeled “low fat” is a faulty practice in cats, just as it is for people. Eating fats doesn’t make your cat fat; eating too many carbs (sugar) does. Leave the fat in the diet, and take out the sugar!

5. Vitamins

Vitamins are either fat soluble (requires fat in the diet to be absorbed) or water soluble. They are involved in numerous chemical reactions that help the body put food to use inside the body. Vitamins are often times lost in the processing of a pet food. So, manufacturers will add in synthetic vitamins after the processing is complete. Synthetic vitamins are not nearly as digestible as the originals.

6. Minerals

A well-balanced diet will provide all the minerals that your cat needs. These needs change based on the animal’s activity level. For example, lactating cats need different minerals at different amounts than a healthy, young adult animal.

Minerals are classified as either “major” or “trace” minerals. Major minerals are required in the diet on a daily basis, and include calcium, phosphorus, magnesium, and sulfur. Trace minerals are not required on a daily basis, and include iron, zinc, copper, selenium and cobalt.

7. Water

Fresh water is always a must. We have already discussed the importance of water in your cat’s diet, and the resulting diseases when there isn’t enough water in the food.

Cats tend to like fresh running water, rather than drinking from a dish. Allowing them to drink from the faucet or purchasing a small water fountain for them to drink from may increase their water intake.

Grey cat is drinking water.
Image Credit: Kevin Nicholson, Catsel

8. Preservatives and Additives

These products are used to preserve, add flavor, and add color to food. Additives are not nutritious and may be detrimental to the cat’s health. There are all-natural preservatives like Vitamin C and Vitamin E.

Read the label. Avoid ingredients like corn syrup, salt, propylene glycol, potassium sorbate, sucrose, propyl gallate, butylated hydroxytoluene (BHT), BHA, sodium nitrate, sodium nitrite, red, yellow or blue dyes, and artificial flavorings.

Cat is checking out food box.
Avoid unhealthy ingredients.

The Bottom Line

  • Proteins are essential and must be from animal sources.
  • Proteins must be quality and digestible. They must be “human-grade.”
  • Carbohydrates need to be kept to a minimum. No grains allowed in cat food!
  • Carbs must be quality and digestible, and from vegetable or fruit sources. Carbs must be “human-grade” and whole.
  • Fats help cats feel full and not overeat.
  • Vitamins and minerals are important and are often lost in the processing of the pet food. Many times, they are replaced with synthetic forms after processing. Synthetic means “man-made” instead of made by nature.
  • Water offered free choice is a must. Using a running water fountain will increase water consumption.
  • Avoid chemical preservatives and additives at all costs!