Objectives: Inadequate dietary folate intake has been implicated in the carcinogenesis of several organs. However, current data differs regarding the role of folate in prostate cancer risk. Alcohol consumption has been associated with increased risk of cancer in several organs as well, yet does not appear to be an independent risk factor for prostate cancer. However, high alcohol intake interferes with folate metabolism. Hence, we hypothesize that the joint effect of low folate intake and high alcohol intake may have a greater impact on prostate cancer risk then the independent effect of either. To address this hypothesis we analyzed folate intake and alcohol consumption in veteran participants in a case-control study of diet and prostate cancer risk. Methods: Prostate cancer cases were recruited upon referral for prostate biopsy and frequency age-matched; PSA normal controls were identified from the VA primary care clinic. Information on folate intake and alcohol consumption were obtained prior to cancer diagnosis using a modified National Cancer Institute Diet History Questionnaire. Alcohol consumption, demographics and other health characteristics were determined using a Risk Factor questionnaire. Dietary folate intake and alcohol consumption was categorized based on the distribution of intake among controls. Other variables were considered for inclusion as covariates and were maintained if they changed the odds ratio of the main predictor variable by greater than 10%. Unconditional logistic regression models were adjusted for age, family history of prostate cancer, race and vitamin B6. Folate intake was modeled as an independent predictor in the entire population and in models stratified by alcohol consumption. Tests for trend were conducted by entering quartiles of folate into the logistic model as different values of a single ordinal variable. Results: Data was analyzed for 137 incident prostate cancer cases, and 238 clinic controls. In multivariate models men in the highest quartile of total folate intake had a 79 percent lower risk of developing disease than men in the lowest quartile of intake. There was no independent association between alcohol consumption and prostate cancer risk. Yet, when stratified by tertile of alcohol intake, the effect of folate was significant only among those with a low to moderate intake of alcohol. Conclusions: Our r esults suggest a significant decrease in risk of prostate cancer with increasing total and dietary folate intake. We report no significant association between supplemental folate intake and prostate cancer risk. In addition, when stratified by alcohol consumption this association remains only in individuals with low to moderate levels of alcohol intake.
- American Association for Cancer Research