Abstract 1265: Carbohydrate intake, glycemic index and prostate cancer risk
Authors: Vidal Adriana C , Williams Christina C , Allott Emma H , Howard Lauren E , Grant Delores J , McPhail Megan , Sourbeer Katharine N , Boffetta Paolo , Hoyo Cathrine , Freedland Stephen J 
Published: May 2015

Background: Reported associations between dietary carbohydrate and prostate cancer (PC) risk are inconsistent and poorly characterized by race. We examined the associations between dietary carbohydrate intake, glycemic index (GI), and PC risk, and whether these associations differed by race.

Methods: We analyzed data from an ongoing case-control study of white (N=262) and black (N=168) veterans at the Durham VA Hospital. Cases were 156 men with biopsy-confirmed PC. Controls were men who had undergone PSA testing but were not recommended for further evaluation. Demographic and lifestyle risk data were collected using self-administered questionnaires prior to diagnosis. Diet information was obtained using the Harvard food frequency questionnaire. Logistic regression models estimated PC risk and results were adjusted for age, race, body mass index BMI and caloric intake.

Results: Among controls, median carbohydrate intake was 224 gms/day, which amounted to 49% (IQR 43-55%) of calories from carbohydrates. Higher total carbohydrate intake was associated with reduced PC risk (3rd tertile vs. 1st tertile, OR=0.29, 95%CI 0.11-0.72, p-trend=0.007). Though associations were similar in black and white men, this only reached significance in black men (p-trend=0.007). When carbohydrate intake was measured as percent of energy from carbohydrates, higher intake was associated with reduced PC risk (3rd tertile vs. 1st tertile, OR=0.57, 95%CI 0.34-0.96, p=0.033). Again, results were similar in both races, though this only reached significance in black men (p-trend=0.025). Similarly, higher fiber intake (p-trend=0.047) was associated with lower risk of PC, with results similar in black and white men. On the contrary, GI was unrelated to PC risk among all men with a suggestion that higher GI may be linked with increased PC risk in black men (p-trend=0.06). When stratified by grade, associations for all dietary factors examined were similar for both low- and high-grade disease.

Conclusion: Among men consuming a Western diet, our findings suggest higher carbohydrate intake and thereby lower intake of other macronutrients (i.e. protein and fat) may be associated with reduced risk of overall PC and both low- and high-grade PC. However, when examining the GI of the diet, though there was no overall association, there was a suggestion that high GI foods may increase PC risk in black men. While larger studies are needed to confirm our findings, especially in black men, these data suggest that among men consuming a Western diet, those eating more complex carbohydrates (i.e. fiber, whole grains) but not refined carbohydrates may have lower PC risk.

Citation Format: Adriana C Vidal, Christina C Williams, Emma H Allott, Lauren E Howard, Delores J Grant, Megan McPhail, Katharine N Sourbeer, Paolo Boffetta, Cathrine Hoyo, Stephen J Freedland. Carbohydrate intake, glycemic index and prostate cancer risk. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1265. doi:10.1158/1538-7445.AM2014-1265