Dietary fat association with nonmelanoma skin cancer among predisposed individuals

Abstract

Although cell and animal studies support an association between nonmelanoma skin cancer and dietary fat, few studies have assessed this relationship among humans. This study assessed the relationship among participants in a five-year chemoprevention trial completed at the Arizona Cancer Center. This design allowed efficient investigation into the association of dietary fat with development of skin basal (BCC) and squamous cell carcinoma (SCC) among high risk individuals. Three manuscripts were written to examine the dietary characteristics of the study population, factors associated with basal and squamous cell skin cancer occurrence, and the association of dietary fat and other dietary components with skin cancer incidence. The hypothesis was that dietary fat, and linoleic acid in particular, would increase the risk of SCC occurrence. Using a semi-quantitative food frequency questionnaire, usual dietary intake of the volunteers, aged 51 to 85 years, was generally consistent with intakes reported by other studies. However, more than half of the participants consumed less than the recommended levels of vitamin D, folate, calcium, and dairy and grain foods. Among participants randomly assigned to the control intervention with no prior history of skin cancer, the incidence of BCC and SCC was 3629 and 2671 per 100,000 person-years, respectively. Only age independently predicted BCC incidence, while male gender, naturally red hair color, years of residency in Arizona as an adult, and age predicted SCC incidence. Dietary fat was not associated with the development of BCC among these high risk individuals. Estimated daily intake of total fat and oleic acid were weakly associated with SCC occurrence (p = 0.09 and p = 0.06) and linoleic acid was not associated. Neither total dietary fat nor any specific fatty acid were associated with reduction in time to first occurrence or total number of skin cancers. Dietary vitamin C and vitamin E, antioxidants that could potentially reduce cellular protein damage from the oxidative compounds formed by ultraviolet penetration, were also not associated with BCC or SCC development.