Endometrial and ovarian cancers represent two of the top ten cancers affecting women in the United States. Experimental and animal models suggest that oxidative stress may play a role in the development of these cancers. Additionally, there is suggestive but limited evidence that dietary antioxidants may be associated with protective effects. To our knowledge, no studies have investigated the synergistic effect of total antioxidant intake with endometrial and ovarian cancer risk. We therefore sought to investigate the role of total antioxidant capacity of the diet using two published antioxidant databases on endometrial cancer and ovarian cancer risk using data from two population-based case-control studies in New Jersey. We also evaluated the association with individual antioxidants, including vitamin E, vitamin C, beta-carotene, selenium, lycopene, and lutein.
For endometrial cancer, using antioxidant capacity estimates derived from an ORAC assay, we found decreased risks for total phenolics (OR: 0.60; 95% CI: 0.38–0.95) and suggested decreased risks for total lipophilic and total hydrophilic antioxidant intake. A suggested decreased risk with the highest tertile compared to the lowest of dietary vitamin E (OR: 0.79; 95% CI: 0.47–1.33), dietary selenium (OR: 0.62; 95% CI: 0.36–1.07), and dietary lycopene (OR: 0.76; 95% CI: 0.50–1.15) were observed, however none reached statistical significance.
For ovarian cancer, an inverse association was observed for the highest compared to the lowest tertile of selenium intake from food sources (OR: 0.41; 95% CI: 0.20–0.81). No association was observed for any other dietary antioxidant. In contrast, a positive association was observed with vitamin C supplement use (OR: 1.63; 95% CI: 1.01–2.62) vitamin E supplement use (OR: 1.63; 95% CI: 1.02–2.63), beta-carotene supplement use (OR: 1.69; 95% CI: 1.08–2.66) and selenium supplement use (OR: 1.64; 95% CI: 1.05–2.56).
Similar results were observed when we used the antioxidant database based on a FRAP assay. Comparisons between the ORAC and FRAP assay-based values revealed differences in the values assigned to food items, mean total daily intake, correlations between individual antioxidants, and between the relative contributions of food items to the indices. However, we found the agreement and the rank order correlation to be high between the two resulting total antioxidant indices.
In conclusion, results from these studies suggest that components of dietary antioxidant intake, mainly total phenolics, total lipophilic antioxidant intake and dietary selenium, may be associated with decreased risks of endometrial and ovarian cancer. Antioxidant supplement intake was associated with increased risks in both studies. Additionally, our findings show that both antioxidant databases may be useful in assessing the total antioxidant capacity of diet in studies of nutritional epidemiology. Further research is needed to confirm these findings.