Cats and Nutrition: Some Key Nutritional Facts

I recently attended a lecture given by by Dr. Deb Zoran of Texas A&M University on the topic of "Protein: the Key to Metabolism, Health, and Management of Obesity in Cats." As you may already know, Deb wrote one of the seminal articles about feline nutrition now over a decade ago (1), and she is a world renowned expert on nutritional needs of cats and how to feed them (2-4). She is a Diplomate of the American College of Veterinary Internal Medicine (currently the President-elect) and also has a PhD in Nutrition.

In this blog post and the next, I'd like to share some of what I learned from Deb's excellent presentation. If you care for cats in your practice, this is all important to know, no matter what the clinical problem.

Feline Nutrition
Cats are obligate carnivores. This statement is news to no one, and yet we often don’t recognize the importance of that statement or feed them accordingly. While cats can use carbohydrates as a source of metabolic energy, they have no requirement for them (nor do dogs for that matter). But, more importantly, because cats evolved consuming prey (e.g., high protein, low to moderate fat, minimal carbohydrate), they are metabolically adapted for higher protein metabolism and lower carbohydrate utilization.

What does that mean metabolically and nutritionally? There are a number of specific metabolic and biochemical differences in feline physiology that are important. This is very important to consider when treating many feline endocrine disorders, especially diabetes and hyperthyroidism.

Cats and Nutrition: Some Key Nutritional Facts

• Cats have an obligate need for protein and amino acids in their daily diet because they are unable to down regulate their urea cycle or transaminases (protein conversion to energy) as other species can in times of starvation.
• Cats utilize protein for energy, even in the face of large amounts of carbohydrates in the diet.
• Taurine, arginine, methionine, cysteine, and possibly carnitine requirements for cats are greater than non-carnivores.
• Arachidonic acid is also an essential fatty acid in cats (it is not in dogs), and is found only in fats from animal tissue.
• Cats require vitamin A and D to be present in the active form in their diet as they are unable to synthesize adequate amounts from other dietary precursors (e.g., carotenoids or vitamin D precursors in skin).
• Cats have an increased need for many B vitamins in their diet (e.g., thiamin, pyridoxine, niacin, pantothenic acid) as they have greater metabolic needs for these vitamins and cannot synthesize or get them from other sources.
• Salivary amylase is absent in cats, and they have greatly reduced levels of intestinal and pancreatic amylases – so carbohydrate digestion is much less efficient.
• Cats have fewer disaccharidases and other brush border enzymes in their small intestine designed to digest and absorb starches.
• The small intestine of cats is much shorter than that of an equally sized omnivore – longer GI tracts are necessary for handling of complex carbohydrates.
• Cats have greatly reduced activities of hepatic enzymes (e.g., glucokinase) designed to convert a post prandial glucose load to glycogen and thus are less able to handle this glucose load.
• There are no fructokinases in cats – they are unable to utilize fructose and other simple sugars.

My Bottom Line

What this list clearly points out that is that cats are not designed to eat carbohydrates as a source of metabolic energy. Instead, cats are metabolically adapted for higher protein metabolism and lower carbohydrate utilization. Therefore, why aren't we all recommending diets (low carb, higher protein) that better meet their needs, and feed cats what they were designed to eat?

References:

1. Zoran DL. The carnivore connection to nutrition in cats. Journal of the American Veterinary Medical Association 2002;221:1559-1567. 
2. Zoran DL, Buffington CAT. Effects of nutritional factors and lifestyle choice on the health and well-being of indoor cats. Journal of the American Veterinary Medical Association 2011;239:596-606. 
3. Zoran DL. The unique nutritional needs of the cat. In: Ettinger SJ, Feldman EC (eds). Textbook of Veterinary Internal Medicine, 7th edition. Saunders Elsevier, 2010;652-659. 
4. Zoran DL. Obesity in dogs and cats: a metabolic and endocrine disorder. Veterinary Clinics of North America Small Animal Practice 2010 Mar;40:221-39.