This study aims to correlate the risk factors of inflammation and antioxidant capacity in cases of colon and breast cancer, using data from a large Spanish case-controlled study (1852 colon cancer subjects, 1567 breast cancer subjects and a total 4933 controls). The role of diet in colon cancer is widely accepted, however it is more controversial with breast cancer where genetic mutations and other lifestyle factors are cited as primary risk factors. What unites these cancers is the inter-related presence of both inflammation and oxidative stress. The dietary inflammatory index (DII®) and non-enzymatic antioxidant capacity (NEAC) were used to evaluate inflammation and oxidative stress using 30 nutrient parameters and 6 inflammatory blood markers. The results showed that colon cancer subjects typically ate a more pro-inflammatory diet compared to controls, with a higher odds ratio of men to women, and tended to be older, heavier and less physically active. The breast cancer subjects also had higher inflammatory scores versus controls but demographically were younger, premenopausal, frequently with a first-degree family link to breast cancer, and including a higher percentage of smokers. For both cancers, inflammation significantly and statistically increased risk factors. Adding in oxidative stress results showed a statistically higher risk of developing colon cancer whilst in breast cancer subjects the risk was increased but non-statistically valid. They did report that meat-eaters had a relative 9% increased risk of Breast cancer. Overall the study concluded that dietary components of inflammation and oxidative stress increased risk of colon cancer but were not statistically valid for breast cancer.