Our primary area of research focuses on the relationship of hormones to cancers of the breast and prostate and how physical activity and diet may affect cancer risk by modifying hormone levels. We have shown previously that postmenopausal women who had elevated serum estrogens and androgens were at a significantly increased risk of developing breast cancer (Cancer Epidemiol. Biomark. Prev. 5:533, 1996). Serum levels of organochlorine pesticides and PCBs that have hormonal effects, however, were not related to risk. Collaborations continue with NCI investigators on the follow-up of this cohort and analysis of serum biomarkers and genetic polymorphisms in relationship to cancer risk. We are also involved in an international pooling project to evaluate the association of serum hormones with breast cancer.
Although physical activity is hypothesized to lower breast cancer risk, we have found that inactive women were not at an increased risk (Am. J. Epidemiol. 139(7):662, 1994). Alcohol ingestion also was not related to risk. However, women consumed only modest amounts of alcohol, and the relationship of light to moderate drinking with breast cancer is controversial. We are currently collaborating with investigators at the U.S. Department of Agriculture and NCI to evaluate the effects of 1 to 2 drinks/day on serum biomarkers, including hormones and micronutrients, to identify mechanisms by which alcohol may influence cancer risk.
Dietary fat has been positively related to prostate cancer risk and we have shown that men had higher serum and urine testosterone levels when they consumed a high fat/low fiber diet (Am. J. Clin. Nutr. 64:850, 1996). However, similar to most cohort studies, our analysis showed that serum androgen and estrogen levels were not related to prostate cancer risk.
Childhood diet has been hypothesized to play a role in the etiology of breast and prostate cancer. To examine this relationship, an ancillary study was initiated to the Dietary Intervention Study in Children to evaluate the effect of an intervention to lower fat intake on serum hormones in boys and girls 8 to 18 years of age. This study has been completed and data analysis is currently ongoing.
A secondary research interest examines the relationships of antioxidant micronutrients and cancer. We have shown that women with higher levels of lycopene, lutein/zeaxanthin, and b-cryptoxanthin were at a lower risk of breast cancer. Collaborations with researchers at NCI and the Centers for Disease Control to evaluate the potential protective effects of antioxidant micronutrients on nonmelanoma skin cancer recurrence are currently underway.