Diet and nutrition as risk factors for multiple myeloma among blacks and whites in the United States

Objectives: To explore whether dietary factors contribute to the risk of multiple myeloma and the two-fold higher incidence among blacks compared to whites in the United States. Methods: Data from a food-frequency questionnaire were analyzed for 346 white and 193 black subjects with multiple myeloma, and 1086 white and 903 black controls who participated in a population-based case-control study of multiple myeloma in three areas of the United States. Results: Elevated risks were associated with obese vs. normal weight (OR = 1.9, 95% confidence interval (CI) = 1.2-3.1 for whites and OR = 1.5, 95% CI = 0.9-2.4 for blacks), while the frequency of obesity was greater for black than white controls. Reduced risks were related to frequent intake of cruciferous vegetables (OR = 0.7, 95% CI = 0.6-0.99) and fish (OR = 0.7, 95% CI = 0.5-0.9) in both races combined, and to vitamin C supplements in whites (OR = 0.6, 95% CI = 0.5-0.9) and blacks (OR = 0.8, 95% CI = 0.5-1.4), with the frequency of vitamin supplement use being greater for white than black controls. However, frequent intake of vitamin C from food and supplements combined was associated with a protective effect in whites (OR = 0.6, 95% CI = 0.4-0.9), but not blacks (OR = 1.2, 95% CI = 0.8-2.1). Conclusions: The greater use of vitamin C supplements by whites and the higher frequency of obesity among blacks may explain part of the higher incidence of multiple myeloma among blacks compared to whites in the United States. In addition, the increasing prevalence of obesity may have contributed to the upward trend in the incidence of multiple myeloma during recent decades.