Dietary intake and the risk of monoclonal gammopathy of undetermined significance: results from the population-based iStopMM screening study.

Monoclonal gammopathy of undetermined significance (MGUS) is the asymptomatic precursor of multiple myeloma (MM) and related disorders. Understanding the causes of MGUS is key to elucidating the causes of these malignancies. The association of MGUS and diet, including dietary patterns, remains unclear. We therefore assessed the relationship between diet and MGUS in the iStopMM a nationwide screening study for MGUS in Iceland where 75,422 individuals have been screened for MGUS. A food-frequency questionnaire was distributed to participants with 27,217 respondents, of whom 1,020 had MGUS at screening. Exposure was defined as dietary intake of specific dietary items and adherence to five dietary patterns identified through principal component analysis. Logistic regression was used to calculate odds ratios (OR) of having MGUS, adjusting for age, sex, physical activity, and education. No dietary patterns nor specific dietary components were associated with risk of MGUS overall. However, high consumption of dairy products was associated with increased odds (OR 2.01, 95% CI 1.16-3.65) of IgA MGUS, even after adjusting for multiple comparisons. These findings suggest that dietary habits are not a major risk factor for MGUS overall and therefore unlikely to be a major causative factor in the development of MM.