Background: Monoclonal gammopathy of undetermined significance (MGUS) is a plasma cell disorder (PCD) with a prevalence of 3% in adults over age 50. The annual risk of progression to multiple myeloma (MM) is 1%. Although one cohort study in Caucasians reported that diets low in certain plant-based foods were associated with MGUS (Thordardottir et al. 2018), research on diet and MGUS in a more diverse population is scarce. Given that diet can vary greatly across ethnic/racial groups, we conducted a population-based study with multiple races and ethnicities. Methods: Using the National Health and Nutrition Examination Survey (NHANES), we conducted a case-control study in 373 individuals with MGUS and 1,406 controls frequency matched on age, body mass index, NHANES cycle, sex, and race. Diet was characterized by one 24-hour dietary recall, with gram intake of individual foods and beverages aggregated into groups. MGUS status was determined by blood screening. Unconditional multivariable logistic regressions were used to model associations between MGUS and intake, with odds ratios and 95% confidence intervals reported for the highest quantile of intake. Results: Daily intake of several food and beverage groups were significantly associated with MGUS, low-risk MGUS (LRMGUS) or intermediate/high-risk MGUS (IHRMGUS). Whole-grain bread, oats, and rice; fruits and vegetables; tomatoes; and cruciferous vegetables were associated with significantly lower risk (28-78%). Sugar- and artificially sweetened beverages were associated with significantly higher risk (34-113%). Interestingly, there were more significant findings for LRMGUS than IHRMGUS, suggesting potential contributing etiologic differences for LRMGUS and IHRMGUS. Conclusions: Our study shows that low intake of whole grains, fruits and vegetables and high intake of sweetened beverages are associated with MGUS. The identification of dietary risk factors for MGUS in a diverse population is of direct public health relevance. These findings also provide rationale for exploration of mechanistic links between diet and PCDs, such as the ongoing studies NCT04920084, NCT05640843, and NCT05312255.

¹ Odds ratios (95% confidence intervals)