Biological effects due to changes in fats during heating

In deep‐fat frying the fat is used over and over again, and moisture and air are mixed into the hot oil. Substantial quantities of the heated fat are absorbed into the fried foods. Many reports from experimental observations with animals fed these fats have shown biological effects ranging from a slight depression in growth, all the way to very poor growth, diminished feed efficiency, increased liver size, fatty necrosis of the liver, and various other organ lesions. Obviously, certain fat constituents may be changed by frying conditions, and the adverse biological effects are relative. We are at the stage in studying these heated fats where selected techniques including biochemical parameters, histopathological evaluations, and tissue culture in monolayers can be good indicators of some of the specific effects on biological tissues. Isolated fractions from heated fat samples, which contained concentrations of cyclic monomer and dimer derivatives, were used in animal studies. Incorporation of the above materials into rat diets produced distended flatulent stomachs and intestines, gastric ulcers, and multiple focal hemorrhages. Histological evaluation of heart, liver, and kidney tissue sections indicated extensive cellular damage. Livers and kidneys exhibited the most severe lesions. Neonatal heart cells established as monolayers on glass cover slips were exposed to fractions from heated or fresh fats. Cellular damage including pyknosis, vacuolization of the cytoplasm, and mitotic aberrations were observed. Uptake of 14 C‐labeled fatty acid by the triglyceride fraction of the cells was increased with heated fats.