Effect of dietary stearic acid on the genesis of spontaneous mammary adenocarcinomas in strain A/ST mice

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Abstract
Strain A/ST female mice maintained on a high fat (15%) diet in which stearic acid was the major lipid component developed initial spontaneous mammary adenocarcinomas at an older age than mice fed a low fat (4.5%) stock diet. Mice placed on the SA diet at weaning developed tumors at 15.7 ± 0.87 months compared to 12.7 ± 0.43 months for those retained on the stock diet (p<.05). Placing mice on the SA diet at 11.5 months resulted in a smaller but significant increase in the latency period (5.0 ± 0.86 vs 3.0 ± 0.57 months ± 0.57 mo), (p< .05). Fatty acid analyses of non‐tumorous mammary tissue from mid‐pregnant mice and of tumor tissues showed that feeding large amounts of 18:0 did not result in increases in the proportion of 18:0. Significant reductions in the percentages of polyun‐saturated fatty acids (PUFA) was found in tissues on mice fed the SA diet. The percentage of 18:2 was reduced in both types of tissues; 20:3 and 20:4 was reduced in tumor tissues. Distribution of C18 fatty acids in plasma membranes of tumors of mice fed the two diets were similar; percentages 18:2 was higher in plasma membranes of non‐tumorous tissues of mice fed the SA diet. These results suggest that dietary stearic acid interferes with the availability of certain PUFA required for tumor production.