RecruitingClinical trialA Study Comparing a Plant-Based Diet With Supplements and Placebo in People With Monoclonal Gammopathy of Undetermined Significance (MGUS) or Smoldering Multiple Myeloma (SMM)The researchers are doing this study to look at how butyrate levels change in participants' stool after they are on a- plant-based diet for at least 12 weeks. All participants will have monoclonal gammopathy of undetermined significance (MGUS) or smoldering multiple myeloma (SMM). We will compare how the plant-based diet, omega-3 fatty acid and curcumin supplements, and placebo (an inactive substance that looks like the study supplements) affect butyrate levels in participants' stool.