The researchers are going this to look at how butyrate levels change in participants' stool after they are on a plant-based diet or dietary supplements (omega-3, curcumin or probiotics) for 2 weeks. All participants will have smoldering multiple myeloma (SMM) or monoclonal gammopathy of undetermined significance (MGUS). The researchers will compare how the different dietary changes affect butyrate levels in participants' stool.

Inclusion Criteria:

• Confirmed prior diagnosis MGUS or of smoldering myeloma (any time prior). However, confirmation of diagnosis must be documented in their last local oncologist clinic note within 6 months prior to study enrollment.
• Age ≥18 years
• Willingness to comply with all study-related procedures
• Physically able to complete requirements for the study or has someone to assist with the requirements (such as meal preparation, stool shipment and survey completion)
• Interested in learning to cook plant-based recipes
• Access to smart mobile phone or device with camera and ability to download Keenoa app
• Be residing within the United States for the study duration.
• English speaking or a family member or caregiver who speaks English and is able to assist with the surveys and phone based Keenoa app.

Exclusion Criteria:

• Taking any supplements other than vitamin D, iron, vitamin B12, potassium, magnesium, calcium or those needed for a medical indication must be reviewed by PI. If patient is on a supplement (including curcumin, probiotic, omega3) they must stop these for 2 weeks prior to enrollment on study.
• Patients that already follow a whole foods plant based diet (ovo-lactovegetarian or processed junk food vegan diets are not excluded). This will be per research dietitian evaluation and discretion after nutrition screening.
• Legume allergy
• Severe allergies such as anaphylactic shock to peanuts and/or tree nuts, such as cashews
• Concurrent participation in weight loss/dietary trials or defined programs (that require specified diets/supplements on the program). Patients on weight loss drugs are eligible.
• Mental impairment leading to inability to cooperate
• Enrollment onto any other therapeutic investigational study
• Concurrent pregnancy
• Patients on full dose anticoagulation
• If in the opinion of the investigator there maybe any concerns regarding the ability of the patient to complete the study safely
• Current self-reported heavy alcohol use and is defined as >5 drinks per day or >15 drinks per week
• Current self-reported illicit drug use (except inhaled marijuana, vaping or cigarette smoking or medical marijuana.
• Has a condition requiring antibiotics within 14 days of study intervention administration.
• Plan for travel during the study that would preclude adherence to prescribed diets
• History of active inflammatory bowel disease or major gastrointestinal surgery (not including appendectomy or cholecystectomy) within 3 months of enrollment or any history of total colectomy, or bariatric surgery (bariatric surgery which does not disrupt the gastrointestinal lumen, i.e. restrictive procedures such as banding, are permitted)

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.