ABSTRACT: Opposing effects of dietary n-3 and n-6 fatty acids
    on mammary carcinogenesis: The Singapore Chinese Health Study
    [10/30/2003; British Journal of Cancer]

We investigated the effects of individual fatty acids
on breast cancer in a prospective study of 35,298 Singapore
Chinese women aged 45-74 years, who were enrolled during
April 1993 to December 1998 (The Singapore Chinese Health
Study). At recruitment, each study subject was administered,
in-person, a validated, semiquantitative food frequency
questionnaire consisting of 165 food and beverage items.
As of December 31, 2000, 314 incident cases of breast
cancer had occurred. We used the Cox regression methods
to examine individual fatty acids in relation to breast
cancer risk, with adjustment for age at baseline interview,
year of interview, dialect group, level of education,
daily alcohol drinking, number of live births, age when
menstrual periods became regular, and family history of
breast cancer. Consumption of saturated, monounsaturated
or polyunsaturated fat overall was unrelated to risk.
On the other hand, high levels of dietary n-3 fatty acids
from fish/shellfish (marine n-3 fatty acids) were significantly
associated with reduced risk. Relative to the lowest quartile
of intake, individuals in the higher three quartiles exhibited
a 26% reduction in risk (relative risk (RR)=0.74, 95%
confidence interval (CI)=0.58, 0.94)); RRs were similar
across the top three quartiles of intake (0.75, 0.75,
0.72, respectively). Overall, there was no association
between n-6 fatty acids and breast cancer risk. However,
among subjects who consumed low levels of marine n-3 fatty
acids (lowest quartile of intake), a statistically significant
increase in risk was observed in individuals belonging
to the highest vs the lowest quartile of n-6 fatty acid
consumption (RR=1.87, 95% CI=1.06-3.27); the corresponding
RR for advanced breast cancer was 2.45 (95% CI=1.20-4.97,
P for trend=0.01). To our knowledge, these are the first
prospective findings linking the intake of marine n-3
fatty acids to breast cancer protection.

The full article can be found at:

http://www.nature.com/cgi-taf/DynaPage.taf?file=/bjc/journal/v89/n9/abs/6601340a.html