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 mu ltiple myeloma and the two-fold higher incidence among blacks compared to w hites in the United States. Methods: Data from a food-frequency questionnaire were analyzed for 346 whi te and 193 black subjects with multiple myeloma, and 1086 white and 903 bla ck controls who participated in a population-based case-control study of mu ltiple 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 blac k than white controls. Reduced risks were related to frequent intake of cru ciferous vegetables (OR = 0.7, 95% CI = 0.6-0.99) and fish (OR = 0.7, 95% C I = 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% C I = 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 hig her frequency of obesity among blacks may explain part of the higher incide nce of multiple myeloma among blacks compared to whites in the United State s. In addition, the increasing prevalence of obesity may have contributed t o the upward trend in the incidence of multiple myeloma during recent decad es.