Glycemic index, glycemic load and endometrial cancer risk: Results from the Australian National Endometrial Cancer study and an updated systematic review and meta-analysis

Purpose: The relationship between habitual consumption of foods with a high glycemic index (GI) and/or a diet with a high glycemic load (GL) and risk of endometrial cancer is uncertain, and relatively few studies have investigated these associations. The objectives of this study were to examine the association between GI/GL and risk of endometrial cancer using data from an Australian population-based case-control study and systematically review all the available evidence to quantify the magnitude of the association using meta-analysis. Methods: The case-control study included 1,290 women aged 18-79 years with newly diagnosed, histologically confirmed endometrial cancer and 1,436 population controls. Controls were selected to match the expected Australian state of residence and age distribution (in 5-year bands) of cases. For the systematic review, relevant studies were identified by searching PubMed and Embase databases through to July 2011. Random-effects models were used to calculate the summary risk estimates, overall and dose-response. Results: In our case-control study, we observed a modest positive association between high dietary GI (OR 1.43, 95 % CI 1.11-1.83) and risk of endometrial cancer, but no association with high dietary GL (OR 1.15, 95 % CI 0.90-1.48). For the meta-analysis, we collated information from six cohort and two case-control studies, involving a total of 5,569 cases. The pooled OR for the highest versus the lowest intake category of GI was 1.15 (0.95-1.40); however, there was significant heterogeneity (p 0.004) by study design (RR 1.00 [95 % CI 0.87-1.14] for cohort studies and 1.56 [95 % CI 1.21-2.02] for case-control studies). There was no association in the dose-response meta-analysis of GI (RR per 5 unit/day increment of GI 1.00, 95 % CI 0.97-1.03). GL was positively associated with endometrial cancer. The pooled RR for the highest versus the lowest GL intake was 1.21 (95 % CI 1.09-1.33) and 1.06 (95 % CI 1.01-1.11) per 50 unit/day increment of GL in the dose-response meta-analysis. Conclusion: The pooled results from observational studies, including our case-control results, provide evidence of a modest positive association between high GL, but not GI, and endometrial cancer risk.