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Nutrition Nuggets is the newest offshoot of petMD's Cat Nutrition Center. Each week Dr. Coates will use her expertise and wisdom to blog about the intricacies of cat nutrition.

Protein Levels in Cat Foods May Be Too Low

September 19, 2014 / (5) comments

A couple of weeks ago we talked about how, unlike many other species, cats need more protein when they enter their golden years (around 12 years of age). In the process of researching that article I came across some disturbing information. The recommendations for minimum protein levels in cat food put forth by the Association of American Feed Control Officials (AAFCO) and the National Research Council (NRC) may be too low.


The NRC’s recommended allowance for protein in adult cat food is 50 g/1,000 kcal metabolizable energy (ME). For kittens, it is 56.3 g/1,000 kcal ME. Now don’t go looking for these sorts of numbers on cat food labels, they’re not there. What does appear on the label is the minimum protein percentage; this is an AAFCO number. The least amount of protein allowable in AAFCO-approved cat foods is 26% for adult maintenance and 30% for growth and reproduction (on a dry matter basis). The AAFCO and NRC numbers are related in that AAFCO uses NRC guidelines to come up with their recommendations.


Research published in 2013 looked at how much protein is needed for cats to maintain their lean body mass (LBM) versus how much is necessary to maintain their “nitrogen balance.” The equation for nitrogen balance is essentially the amount of nitrogen taken in minus the amount of nitrogen lost from the body. A negative nitrogen balance (more lost than taken in) is obviously an unsustainable situation and is associated with protein-losing conditions or malnutrition.


Twenty-four adult, neutered male cats were included in this study. For one month, all of the cats ate a 34% protein diet. After this baseline period, the cats were fed a low protein (20%), moderate protein (26%), or high protein (34%) diet for two months. The results revealed that only 1.5 g protein/kg body weight was needed to maintain the cats’ nitrogen balance, while 5.2 g protein/kg body weight was necessary to avoid a loss in lean body mass. The authors concluded that:


This study provides evidence that nitrogen balance studies are inadequate for determining optimum protein requirements. Animals, including cats, can adapt to low protein intake and maintain nitrogen balance while depleting LBM. Loss of LBM and an associated reduction in protein turnover can result in compromised immune function and increased morbidity [disease]. Current Association of American Feed Control Officials (AAFCO) and National Research Council (NRC) standards for protein adequacy may not provide adequate protein to support LBM. The minimum daily protein requirement for adult cats appears to be at least 5.2 g/kg (7.8 g/kg(0.75)) body weight, well in excess of current AAFCO and NRC recommendations.


The take home message from this study? Most cats should be eating foods that contain significantly more protein than the minimum currently put forth by AAFCO. A precise number is hard to recommend, but personally I look for dry foods with at least 30% protein supplemented with a 40-50% protein canned food. When cats have access to both, they are very good at balancing their own diets.


Jennifer Coates



Discrepancy between use of lean body mass or nitrogen balance to determine protein requirements for adult cats. Laflamme DP, Hannah SS. J Feline Med Surg. 2013 Aug;15(8):691-7.


Image: Zizar / Shutterstock


Comments  5

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  • Good to Know
    09/19/2014 09:36pm

    As my small herd grows older, this is especially relevant. Two of my three turned 11 years old last month, so I'm going to start watching the protein levels a lot more closely.

    Thanks so much!

    09/20/2014 07:55pm

    Hi Dr. Coates,
    Please (please, please) go to AAFCO meetings and share your concern with the Pet Food Committee. The next meeting is in Texas in January. Dr. William Burkholder of FDA who is a member of AAFCO's Pet Food Committee would also be a key person to contact and share your low protein concern with. Pet food consumers need more veterinarians to advocate for them - right now we have only one veterinarian as adviser to this committee (Dr. Jean Hofve). The last meeting two more veterinarians were in attendance speaking up for safer pet food regulations (Dr. Oscar Chavez and Dr. Cathy Alinovi) - but we need more. Industry has hundreds of representatives at each meeting - consumers have only a handful. To make changes, we need our veterinarians to step forward and work with those that develop these regulations. I hope to see you in Texas this January.
    Susan Thixton
    Consumer Advocate

  • Meat vs. Plant Protein
    09/20/2014 09:07pm

    As far as I know, the "protein" levels count both meat and plant protein, but those things are by no means equal. Foods with corn, wheat, etc. may have made the plant protein somewhat more digestible, but the increase in carb levels is certainly not worth it. And when you consider how much companies such as Hills spend annually to convince people that corn and wheat are acceptable, it's little wonder that the diabetes problems are growing.

    We need more than better protein standards. We need laws that punish companies for fraudulent claims or paying for studies that are clearly designed to bypass potential problems and return a result favorable to the company. In the meantime, we just have to learn to do our own thinking rather than letting the food companies....or even vets....do our thinking for us. I lost two of the finest souls I've ever met just because I never stopped to think about cats as obligate carnivores and what that really means.

  • 09/24/2014 03:18am

    Hills has a entire line of natural food that is no corn, no soy, no wheat. It's called Ideal Balance. But then their Science Diet is all natural as well, but does have corn and wheat in it too. But for those that are sure they don't want any of that in their food, they do have a extensive line that doesn't have corn, soy or wheat.
    Maybe you don't know that?

  • 09/24/2014 01:51pm

    Sure, Hills came out with a grain-free food once it became clear that they would have to do so in order to compete, but they are still pushing all their high carb foods and claiming they are good.