Andrew from Greenfield Animal Hospital

General Information:

Cats are obligate carnivores and are metabolically designed to consume diets with the following general composition (keep in mind that 100% of a diet’s calories come from protein, fat, and carbohydrate):

  •    animal (not plant) based protein making up greater than 50% of total calories
  •    moderate fat making up roughly 20-45% calories
  •    very low carbohydrate accounting for less than 7-10 % calories
  •    water-rich (about 70%)

Is canned or dry food better?

Canned food diets are preferable as only canned foods provide the proper water content to maintain your pet’s hydration. Cats have a low thirst drive and are designed to get their water needs met by their prey or food bowl. Canned foods promote urinary tract health and optimal systemic hydration which is especially critical for cats with kidney insufficiency.

What if my cat will only eat dry foods?

Cats fed dry food diets tend not to drink enough to maintain proper hydration which can lead to kidney disease. If your cats will only eat dry food diets, consider adding water fountains to provide running water or even adding water to the dry food to encourage better hydration.

Isn’t dry food better for my cats teeth?

It is a myth that dry food diets prevent tartar formation and most cats only chew 10% of their food. The propensity for tartar has more to do with genetics and dental home care is the only sure fire way to reduce tartar formation. Please be sure to ask about dental home care at your next visit.

How do I know if animal based protein is the main ingredient?

Generally, it is best to look at the ingredients list for meat (chicken, pork, duck, etc) as the first and possibly the first several ingredients. Ingredients are listed in descending order by their weight so a diet that starts with chicken as the first ingredient is preferable to one that starts with a vegetable or starch.  In addition, avoid diets that do not have meat, but rather have instead have meal (ie – chicken meal or pork meal) as this is a less nutritious food. Finally, meat by product is a good source of nutrition and should be included in pet foods, but it is inferior to meat alone, so ideally the diet would contain meat ahead of by product on the ingredients list.

How do we know how much of the protein is coming from animals versus plants when an ingredient list includes both animals and plant (grain/potatoes/vegetables) protein sources?

The answer is we do not know but we need to be aware of the ingredient splitting issue. Ingredients on labels are listed in descending order by weight. For example – “chicken, brewers rice, corn gluten meal, whole grain corn, wheat gluten”. Consumers often focus on the fact that “chicken” is the first ingredient but when the grain fractions are added together, their contribution to the diet is greater than the meat.

Are Grain-free diets better?

The Grain-free movement is largely a marketing ploy, although it can mean the food is superior. “Grain-free” does not necessarily mean “low-carb”. Potatoes and peas are often used in “grain free” products which “may” result in a higher carbohydrate diet. The ingredient list does not tell you how much potato, rice, vegetable matter, etc., is in a product. If the diet is low in carbohydrates, there can’t be much of those ingredients in the product. Note that “gravy” foods tend to be high in carbohydrates.

 How about feeding fish-based diets?

As a general rule, fish based diets are not favored for several reasons:

  •         high allergy potential
  •         toxins/mercury levels
  •         PBDE levels (fire retardant chemicals with thyroid-disrupting properties)
  •         often high in phosphorus and magnesium
  •         significant addiction issues, i.e. the cat will not eat anything else.

Is an all natural diet better?

The main difference in an all natural diet is the lack of food coloring, artificial flavors and synthetic preservatives. For most diets, there are no artificial flavors or food coloring, so ultimately the all natural label has to do with preservatives used. All natural diets use natural preservatives that are generally less effective so you run the risk of having spoiled foods. There is no known negative health effect of commonly used synthetic preservatives, but this can of course change with additional research. Use your judgment.


  • Consider avoiding diet companies that do not make general nutritional information readily available other than those required to be on the nutrition label by law.

Much of the information provided in this handout is borrowed from Dr. Lisa Pierson and the website On her website, Dr. Pierson has a link to a Protein/Fat/Carb/and Phosphorus chart which lists the relative percentage of each for most available canned foods.