A prospective study of polyunsaturated fatty acid levels in blood and prostate cancer risk.
BACKGROUND
Animal models suggest that n-3 fatty acids inhibit prostate cancer proliferation, whereas n-6 fatty acids promote it, but epidemiologic studies do not uniformly support these findings.


METHODS
A nested case-control study was conducted among 14,916 apparently healthy men who provided blood samples in 1982. Blood fatty acid levels were determined for 476 men diagnosed with prostate cancer during a 13-year follow-up and their matched controls. Conditional logistic regression was used to estimate the relative risks (RR) and 95% confidence intervals (95% CI) of total, non-aggressive (stage A/B and Gleason < 7) and aggressive (stage C/D, Gleason >or= 7, subsequent distant metastasis or death) prostate cancer associated with blood levels of specific fatty acids expressed as percentages of total fatty acids.


RESULTS
Whole blood levels of all long-chain n-3 fatty acids examined and of linoleic acid were inversely related to overall prostate cancer risk (RR(Q5vs.Q1), 0.59; 95% CI, 0.38-0.93; P(trend) = 0.01 for total long-chain n-3 fatty acids and RR(Q5vs.Q1), 0.62; 95% CI, 0.41-0.95; P(trend) = 0.03 for linoleic). Blood levels of gamma-linolenic and dihomo-gamma-linolenic acids, fatty acids resulting from the metabolism of linoleic acid, were directly associated with prostate cancer (RR, 1.41; 95% CI, 0.94-2.12; P(trend) = 0.05 for gamma-linolenic and RR, 1.54; 95% CI, 1.03-2.30; P(trend) = 0.02 for dihomo-gamma-linolenic acid). Levels of arachidonic and alpha-linolenic acids were unrelated to prostate cancer.


CONCLUSIONS
Higher blood levels of long-chain n-3 fatty acids, mainly found in marine foods, and of linoleic acid, mainly found in non-hydrogenated vegetable oils, are associated with a reduced risk of prostate cancer. The direct associations of linoleic acid metabolites with prostate cancer risk deserve further investigation.
Chavarro
Jorge E
JE
Department of Nutrition, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA. jchavarr@hsph.harvard.edu
Stampfer
Meir J
MJ
Li
Haojie
H
Campos
Hannia
H
Kurth
Tobias
T
Ma
Jing
J
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004311:Double-Blind Method; D005231:Fatty Acids, Unsaturated / Q000097:blood*; D006801:Humans; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D010919:Placebos; D011446:Prospective Studies; D011467:Prostate; D011471:Prostatic Neoplasms / Q000097:blood* / Q000453:epidemiology; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
D005231:Fatty Acids, Unsaturated; D010919:Placebos