Our research has focused on the etiology of cancers, particularly malignancies of the colorectum and prostate. Our recent studies have helped clarify the causes of colorectal cancer. We have found that a diet high in red meat and alcohol, and low in folate and methionine increases risk of this malignancy. Also, physical activity and regular use of aspirin appear to decrease risk, and smoking increases risk. We are currently examining whether folate supplementation reduces risk of recurrent colorectal adenomas in a randomized, intervention trial. We are also studying the hypothesis that alcohol, folate and methionine, and genetic factors related to their metabolism, interact to influence risk of colorectal cancer by affecting DNA methylation.
We also plan to explore whether high levels of insulin and insulin-like growth factor promote colon cancers. Our other main line of research involves prostate cancer. We have found that high intake of animals fats and low intake of lycopene, a carotenoid found in tomatoes, are probably important in causing prostate cancer. We plan to collect prostate tumor tissue to study these relationships in more detail.