Answers: Lysine and Raw Meat Diets
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- Last Updated on Sunday, March 15, 2015 06:17 PM
- Published on Saturday, March 07, 2015 05:49 PM
- Written by Elisa Katz, DVM
What is lysine? I have a friend who gives it to her cat as a treatment for herpes, but should it be supplemented in every cat's diet?
Lysine is an essential amino acid for cats. This means that the cat's body cannot synthesize or make this amino acid so it must be consumed in the diet. Lysine is present in all meats, but fish contain higher amounts than other types of meat. For many years in human medicine lysine has been used to help suppress herpes flare ups and several studies exist to support this.¹ It is suspected that the mechanism by which lysine is able to suppress herpesvirus is by competing with arginine. Studies have indicated that arginine is necessary to signal and initiate replication of certain viruses including all herpesviruses. It is thought that lysine displaces arginine and thus interferes with this process. Several studies indicate that lysine may be effective at suppressing feline herpesvirus, a common cause of upper respiratory and eye problems in cats.²
Since arginine is also an essential amino acid for the cat, there has been some concern that too much lysine may result in an arginine deficiency. Arginine deficiency can make cats very sick. See "What is Arginine and Is It Essential?" for more information on that. However, a 2004 study of 36 cats concluded that lysine supplementation of up to 86 g/kg showed no adverse effects.³This would equate to the average 4.5 kg, or 10 pound, cat receiving 387 g or 387,000 mg per day. Given that the recommended treatment dose is 500 mg twice daily, there seems to be no cause for concern regarding arginine deficiency in cats appropriately supplemented with lysine. While the study covered a 14 day period it can be assumed that due to the enormous difference between the threshold of lysine resulting in any adverse effect and the typical dose, long term usage is extremely unlikely to result in any unwanted effects.
According to the National Research Council the minimum daily requirement of lysine for an adult cat is 0.68 g per 1,000 kcal of metabolizable energy.⁴ Since most cats require in the range of 300-350kilocalories per day, the minimum requirement for most cats should be about 0.20-0.25 g, which is 200 to 250 mg and equivalent to 0.0088 ounce. The NRC does not list a maximum daily amount. Most meat sources including poultry, beef, and fish have at least 230 mg of lysine per 100 grams/3.5 ounces of meat. Since most cats will consume at least 4 ounces of meat per day, there is more than enough lysine in a meat-based diet to meet a cat's daily need.⁵