Plant-based, high-fiber diets and the gut microbiome in smoldering multiple myeloma

A Prospective Multicenter Study of the Effects of Plant-based Diets on Gut Microbiome and Derived Metabolites in Patients Affected by Smoldering Multiple Myeloma

This 12-week program will try a high-fiber plant-based diet in people with smoldering multiple myeloma to see if it changes gut bacteria and raises short-chain fatty acids.

Quick facts

• Phase: Not applicable
• Study type: Interventional
• Enrollment: 62 (estimated)
• Ages: 18 Years to 75 Years
• Sex: All
• Sponsor: IRCCS San Raffaele (Academic / other)
• Locations: 5 sites (Milan, Milano and 4 other locations)
• Trial ID: NCT07069751 on ClinicalTrials.gov

What this trial studies

This is a prospective, multicenter intervention in Italy enrolling up to 62 patients with smoldering multiple myeloma, with 56 eligible participants encouraged to follow a balanced, fiber-rich plant-based diet for 12 weeks. Participants choose from several diet plans or individual foods to match personal preferences and receive nutritional counseling at enrollment, at one month, and on demand. Clinical visits and sample collection occur at enrollment and at week 12 to analyze gut microbiome composition, short-chain fatty acid production, and immune markers such as CD8/Th17 ratios. The protocol aims to document microbiome shifts associated with increased SCFA production and explore whether these changes correlate with biomarkers linked to progression risk.

Who should consider this trial

Good fit: Adults aged 18–75 with confirmed smoldering multiple myeloma by IMWG criteria, ECOG 0–1, willing to follow dietary counseling and study procedures, and not already following a whole-food plant-based diet are ideal candidates.

Not a fit: Patients who already eat a high–fiber whole-food plant-based diet, those with legume or severe nut allergies, or patients excluded by the protocol (including non-Caucasian individuals per the eligibility criteria) are unlikely to benefit from or be eligible for the intervention.

Why it matters

Potential benefit: If successful, the intervention could lower biological risk markers linked to progression and suggest a non-drug approach to reduce the chance of progressing to active multiple myeloma.

How similar studies have performed: Dietary fiber and plant-based interventions have previously been shown to change gut microbiota composition and increase SCFA levels in other populations, but using such diets specifically to prevent progression from smoldering to active myeloma is largely untested.

Eligibility criteria

Inclusion Criteria:

1. Participant is willing and able to give informed consent for participation in the study.
2. Confirmed diagnosis of sMM according to IMWG criteria
3. Absence of features of symptomatic or active myeloma requiring treatment (myeloma-defining events).
4. Aged ≥18 and \</= 75 years
5. Participant is willing to comply with all study-related procedures.
6. ECOG performance status of 0-1.

Exclusion Criteria:

1. Non-Caucasian subjects. Racial disparities in all stages of the disease characterize MM, and Blacks have an increased MGUS and MM risk and higher mortality rate than Whites.
2. Patients that already follow a whole food plant-based diet (≥ 40g/die;ovo-lacto-vegetarian or processed junk food vegan diets are not excluded). These patients likely should already have high SCFA levels in their gut.
3. Legume allergy.
4. Severe allergies such as anaphylactic shock to nuts (specifically cashews).
5. Concurrent participation in weight loss/dietary/exercise programs because of potential conflicts between the concurrent diet and high-fiber diet.
6. Enrollment onto any other therapeutic investigational study.
7. Concurrent pregnancy.
8. Ongoing treatment for HBV, HCV or HIV.
9. If in the opinion of the investigator there maybe any concerns regarding the ability of the patient to complete the study safely or any contraindications.
10. Heavy drinker (defined as \>2 drinks per day or \>14 drinks per week).
11. Current self-reported illicit drug use (e.g., heroin, cocaine not marijuana).
12. Subjects that did not accept to sign the informed consent.
13. Subjects reporting infectious diseases requiring antibiotic therapy in the previous three months, ongoing antibiotic therapy, or prophylaxis. Antibiotic therapy dramatically modifies the composition of the gut microbiota.
14. Subjects affected by autoimmune diseases except for thyroiditis, and patients affected by small and large intestine dysfunctions (i.e., inflammatory bowel disease).
15. Gammopathy-associated conditions beyond sMM (e.g. amiloydosis, POEMS, LCDD, etc).

Where this trial is running

Milan, Milano and 4 other locations

• IRCCS Ospedale San Raffaele — Milan, Milano, Italy (Recruiting)
• Ospedale Giovanni XXIII Policlinico di Bari — Bari, Italy (Not_yet_recruiting)
• Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico — Milan, Italy (Not_yet_recruiting)
• Fondazione IRCCS Istituto Nazionale dei Tumori — Milan, Italy (Not_yet_recruiting)
• Azienda Ospedaliero Universitaria di Parma — Parma, Italy (Not_yet_recruiting)

Study contacts

• Study coordinator: Tommaso Perini

Conditions Smoldering Multiple Myeloma; microbiome; plant-based diets; gut microbiome; smoldering multiple myeloma