The relation of a-linolenic acid to the risk of prostate cancer: a systematic review and meta-analysis.
The relation of a-linolenic acid to the risk of prostate cancer: a systematic review and meta-analysis.
Year: 2009
Authors: Simon, J.A. Chen, Y-H. Bent, S.
Publication Name: Amer. J. Clin. Nutr.
Publication Details: Vol. 89; Pages 1558S – 64S.
Abstract:
Alpha-Linolenic acid (ALA; 18:3n23) has been associated inconsistently with an increased risk of prostate cancer. Additional studies have become available since the publication of 2 previous meta-analyses. The objective was to review the published data on the relation between ALA and prostate cancer. We conducted a systematic review to identify studies that included data on ALA and risk of prostate cancer. Data were pooled from studies that compared the highest ALA quantile with the lowest ALA quantile, and risk estimates were combined by using a random-effects model. The relation between ALA and prostate cancer is inconsistent across studies. We pooled data from 8 case-control and 8 prospective studies. The summary estimate revealed that high ALA dietary intakes or tissue concentrations are weakly associated with prostate cancer risk (relative risk [RR]: 1.20; 95% CI: 1.01, 1.43). When examined by study type (i.e. retrospective compared with prospective or dietary ALA compared with tissue concentration)
or by decade of publication, only the 6 studies examining blood or tissue ALA concentrations revealed a statistically significant association. With the exception of these studies, there was significant heterogeneity and evidence of publication bias. After adjustment for publication bias, there was no association between ALA and prostate cancer (RR: 0.96; 95% CI: 0.79, 1.17). Studies examining the relation between ALA and prostate cancer have produced inconsistent findings. High ALA intakes or high blood and adipose tissue concentrations of ALA may be associated with a small increased risk of prostate cancer. However, these conclusions are qualified because of the heterogeneity across studies and the likelihood of publication bias. (Author's abstract)
The importance of dietary risk factors, such as high intakes of total fat and n6 (omega-6) fatty acids and low intakes of vitamin E, selenium, lycopene, and fish oil n?3 fatty acids, on prostate cancer risk is controversial. In particular, ALA has been reported, albeit inconsistently, to be associated with an increased risk of prostate cancer. In this report, a meta-analysis of data related to ALA and prostate cancer is conducted. When all studies were considered together, when compared with men in the lowest ALA quantile, men in the highest ALA quantile had 20% increased risk of prostate cancer. There was, however, significant heterogeneity among the studies and evidence for publication bias. Generally, prospective studies are less prone to bias than retrospective studies and among these investigations no evidence linking ALA with an increased risk of prostate cancer was found. The studies that used dietary intake estimates, when pooled, revealed no evidence linking ALA with an increased risk of prostate cancer whereas those that used blood or tissue markers suggested a 54% increased risk. Of the other studies that reported on the relation of ALA to prostate cancer but did not provide data suitable for meta-analysis, the majority found no significant association. The authors offer their best estimate on the basis of all available data, that there may be a small increased risk of prostate cancer at the highest levels of ALA consumption. These conclusions must be considered highly qualified, however, because of the heterogeneity across the studies and the probability of publication bias with the absence of smaller negative studies. Additional in vitro research and careful population studies may over time provide additional evidence to help answer this question more definitively. (Editor's comments)
or by decade of publication, only the 6 studies examining blood or tissue ALA concentrations revealed a statistically significant association. With the exception of these studies, there was significant heterogeneity and evidence of publication bias. After adjustment for publication bias, there was no association between ALA and prostate cancer (RR: 0.96; 95% CI: 0.79, 1.17). Studies examining the relation between ALA and prostate cancer have produced inconsistent findings. High ALA intakes or high blood and adipose tissue concentrations of ALA may be associated with a small increased risk of prostate cancer. However, these conclusions are qualified because of the heterogeneity across studies and the likelihood of publication bias. (Author's abstract)
The importance of dietary risk factors, such as high intakes of total fat and n6 (omega-6) fatty acids and low intakes of vitamin E, selenium, lycopene, and fish oil n?3 fatty acids, on prostate cancer risk is controversial. In particular, ALA has been reported, albeit inconsistently, to be associated with an increased risk of prostate cancer. In this report, a meta-analysis of data related to ALA and prostate cancer is conducted. When all studies were considered together, when compared with men in the lowest ALA quantile, men in the highest ALA quantile had 20% increased risk of prostate cancer. There was, however, significant heterogeneity among the studies and evidence for publication bias. Generally, prospective studies are less prone to bias than retrospective studies and among these investigations no evidence linking ALA with an increased risk of prostate cancer was found. The studies that used dietary intake estimates, when pooled, revealed no evidence linking ALA with an increased risk of prostate cancer whereas those that used blood or tissue markers suggested a 54% increased risk. Of the other studies that reported on the relation of ALA to prostate cancer but did not provide data suitable for meta-analysis, the majority found no significant association. The authors offer their best estimate on the basis of all available data, that there may be a small increased risk of prostate cancer at the highest levels of ALA consumption. These conclusions must be considered highly qualified, however, because of the heterogeneity across the studies and the probability of publication bias with the absence of smaller negative studies. Additional in vitro research and careful population studies may over time provide additional evidence to help answer this question more definitively. (Editor's comments)
