My research focuses on how nutritional, genetic, environmental and lifestyle factors relate to various malignancies, especially those of the prostate and large bowel. Much of my work is centered on large ongoing cohort studies, including the Nurses’ Health Study, the Health Professionals Follow-Up Study and the Physicians’ Health Study. A specific area of interest is the etiologic mechanisms underlying the relation between modifiable factors and cancer risk. My work has included the study of how nutrition and other lifestyle factors impact on cancer risk and progression by influencing levels of insulin, insulin-like growth factors, vitamin D metabolites, and steroid hormones. Another area of interest is how nutrients may interact with genetic susceptibilities in determining an individual's risk. Recent publications include investigations of the role of vitamin D levels in myocardial infarction, prostate cancer, and in the survival of patients with colorectal cancer.