A comparative study of serum linoleic acid in prostate cancer risk between African-Americans and Africans.

A51

Introduction: There is some evidence that higher dietary intake and blood level of linoleic acid are associated with a reduced risk of prostate cancer but findings have been conflicting. Prostate cancer incidence rate for African-Americans is five times that of African-Nigerians with similar rates found at autopsy. We compared the serum linoleic acid (C18:2) levels to elucidate the prostate cancer risk disparity between these two populations.
 Methods: A case-control study was conducted among 458 men, Nigerians (N=311) from the community and urology clinics at University of Benin Teaching Hospital, and African-Americans (N=147) from Washington DC and Nashville, Tennessee area who provided fasting blood samples. Quantitative measurement of serum linoleic acid levels and other abundant fatty acids were done using capillary gas chromatography. Logistic regression was used to compute adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) to measure the strength of associations in the highest quartile of serum linolenic acid (µg/ml) level in relation to the lowest quartile for each population.
 Results: Mean age of Nigerians compared to African-Americans was 60.7±13.8 to 57.1±9.7, p<0.001. Among Nigerian median total fatty acids and n-6 fatty acids were lower (2,439 μg/ml to 2,654 µg/ml, p<0.0001; 666 μg/ml to 1,103 μg/ml, p<0.0001 respectively), while n-3 fatty acids were higher (101 μg/ml to 85 μg/ml, p<0.0001) in comparison to African-Americans. Serum linoleic acid was inversely related to overall prostate cancer risk (OR_Q4vs.Q1, 0.32; 95%CI, 0.11-0.96; P _trend=0.04 among African-Americans and was not related to prostate cancer risk (OR_Q4vs.Q1, 4.00; 95%CI, 0.98-16.42; P _trend=0.20) among Nigerians.
 Conclusions: Our study suggests that there are some significant differences exist in the fatty acid profiles between African-Americans and Nigerians. The comparatively low incidence of prostate cancer in Nigeria may be related to the lower n-6 and higher n-3 fatty acids levels in blood. The apparent protective effective of serum linoleic acid was found for African-Americans but not consistent for Nigerians. The direct association of linoleic acid metabolites with prostate cancer risk are needed to be further investigated in these disparate populations.