From "The Encyclopedia of Natural Pet Care" by C. J. Puotenin
Using Cooked Foods: A Strategy for Avoiding Leucocytosis
In the 1930's, the French chemist Paul Kouchakoff discovered that as soon as cooked or processed food is tasted, white blood cells rush to the intestines. This phenomenon, called digestive leucocytosis, disrupts the immune system; the body regards cooked food as a pathogen and works hard to destroy it. When Kouchakoff's volunteers ate raw food, their white blood cells remained in place. As Leslie and Susannah Kenton wrote in "Raw Energy", the implications of leucocytosis are that every time white blood cells flock to the intestines to deal with cooked food, the rest of the body is left undefended. "Continual red alerts, three or more times a day, year in and year out," they observed, "put considerable strain on the immune system." Unlike cooked foods, raw foods leave the white blood cells free for other tasks, "thus saving the body considerable effort while strengthening its resistance to disease".
However, if you eat something cooked after eating something raw, leucocytosis doesn't happen. The body responds only to the first bite of food. For that reason it's sensible to begin every meal with a taste of something raw. If you have to feed your pet something that has been pasteurized, baked, canned, boiled or heated well above body temperature, give him or her a raw food first, such as a carrot or even a piece of grass to nibble on.
Cooked food should always be accompanied by digestive enzyme supplements.