Fatty-acid composition in serum phospholipids and risk of breast cancer: An incident case-control study in Sweden

The study of the relationship between dietary intake of fatty acids and the risk of breast cancer has not yielded definite conclusions with respect to causality, possibly because of methodological issues inherent to nutrition al epidemiology. To evaluate the hypothesis of possible protection of n-3 p olyunsaturated fatty acids (PUFA) against breast cancer in women, we examin ed the fatty-acid composition of phospholipids in pre-diagnostic sera of 19 6 women who developed breast cancer, and of 388 controls matched for age at recruitment and duration of follow-up, in a prospective cohort study in Um ea, northern Sweden. Individual fatty acids were measured as a percentage o f total fatty acids, using capillary gas chromatography. Conditional logist ic-regression models showed no significant association between n-3 PUFA and breast-cancer risk. In contrast, women in the highest quartile of stearic acid had a relative risk of 0.49 (95% confidence interval, 0.22-1.08) compa red with women in the lowest quartile (trend p = 0.047), suggesting a prote ctive role of stearic acid in breast-cancer risk. Besides stearic acid, wom en in the highest quartile of the 18:0/18:1 n-9c ratio had a relative risk of 0.50 (95% confidence interval, 0.23-1.10) compared with women in the low est quartile (trend p = 0.064), suggesting a decrease in breast-cancer risk in women with low activity of the enzyme delta 9-desaturase (stearoyl CoA desaturase), which may reflect an underlying metabolic profile characterize d by insulin resistance and chronic hyper-insulinemia. (C) 1999 Wiley-Liss, Inc.