Influence of dietary fatty acids on the incidence of mammary tumors in the C3H mouse.

Statistical techniques have been used to establish the extent to which the incidence of spontaneous mammary tumors in C3H mice could be associated with the levels of individual fatty acids in their diets. Eleven different fats and oils and nine mixtures of these fats and oils were selected so that the levels of the nine major fatty acids varied over a reasonable range and were not highly correlated with one another. Tumor incidence was observed in mice raised on diets containing 10% of these different fats. Multiple regressions have been calculated, expressing tumor incidence or time to tumor as a function of the levels of nine fatty acids, four saturated and five unsaturated, of the dietary lipids. Increased tumor incidence and decreased time to tumor were observed when increasing levels of linoleate (18:2) replaced the eight other fatty acids in the diet while the other polyunsaturated fatty acid, linolenate (18: 3), had little effect on tumor incidence. Four saturated fatty acids, laureate (12:0), myristate (14:0), palmitate (16:0), and stearate (18:0), were studied, with only the latter showing a significant effect. Increasing levels of stearate were associated with decreased tumor incidence and increased time to tumor. There was also a suggestion that erucic acid (22:1) reduced tumor incidence, but oleic acid (19:1) produced no significant effect.