Assessing the effect of fatty acids on prostate carcinogenesis in humans: does self-reported dietary intake rank prostatic exposure correctly?

Background: Dietary fatty acids may influence prostate carcinogenesis. Alth ough the standard for assessing dietary effects in humans is the semiquanti tative food-frequency questionnaire, the extent to which self-reported inta ke correctly ranks prostatic exposure is unknown. Objective: The objective was to examine the correlation between reported in takes of different fatty acids and their concentrations in prostate tissue. Design: This was a cross-sectional study of 52 men undergoing surgical rese ction of the prostate gland. Usual dietary intake of saturated, total unsat urated, oleic, and linoleic fatty acids over the previous year was estimate d with use of a 122-item version of the Health Habits and History Questionn aire. Concentrations in prostate tissue were measured directly by use of ga s chromatography in healthy tissue collected at the time of surgery and wer e expressed as a percentage of total fatty acids. Correlations with 4 measu res of dietary intake [g/d, g/d adjusted for total daily energy intake, % o f total fat (as g/d), and % of total energy] were evaluated by Spearman's r ank-order correlation coefficients. Results: Linoleic acid concentrations in prostate tissue were significantly correlated with dietary intake expressed as g/d adjusted for total energy [r = 0.29 (95% CI: 0.03, 0.9), P = 0.04], % of total fat [r = 0.36 (0.14, 0 .550), P = 0.008], and % of total energy [r = 0.28 (0.04, 0.49), P = 0.042] but not as g/d. Although mean concentrations of saturated, total unsaturat ed, and oleic fatty acids in prostate tissue resembled mean intakes for the group, prostatic concentrations did not correlate with individual intakes. Conclusion: Self-reported intake of fatty acids is a satisfactory marker of prostatic exposure at the group level, but, with the exception of linoleic acid, does not correctly rank individuals with respect to intensity of exp osure.