High-Fiber Diet May Delay Progression of Multiple Myeloma in Patients With MGUS, SMM

Research published in Cancer Discovery suggests that a high-fiber, plant-based diet delayed progression of multiple myeloma (MM) in patients with monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). The findings, which are from the NUTRIVENTION clinical trial (NCT04920084), showed that a high-fiber diet improved metabolism and microbiome composition, leading to improved antitumor immunity and inhibited tumor growth.^1,2

What is Multiple Myeloma, and How Does it Progress?

MM is a cancer that derives from a type of white blood cell called a plasma cell, which is produced in the bone marrow. It often develops from precursor conditions, such as MGUS and SMM, which may or may not develop into full MM.

MGUS is an early, usually asymptomatic stage marked by the presence of an atypical presence of M proteins in the blood, with about a 1% annual risk of progression to MM. SMM is an intermediate stage with a higher progression risk—approximately 10% per year, especially in the first 5 years after diagnosis—and is genomically distinct from MM.³

For patients who are concerned about their disease developing into MM, they may take initiatives or steps to mitigate the progression of the disease. For some, this might involve lifestyle modifications, such as adjusting diet.

What Did the NUTRIVENTION Clinical Trial Investigate?

NUTRIVENTION assessed whether a high-fiber, plant-based diet is practical or feasible for 20 individuals with overweight and MGUS or SMM. Specifically, the researchers determined how practical the diet is for patients by looking at how much weight participants lose and how well they are able to adhere to the diet. The feasibility of the diet was determined based on its effects on improving quality of life and modifiable risk factors, including metabolic factors (eg, body mass index [BMI], insulin resistance), microbiome diversity and composition, and immune factors (eg, inflammation, monocyte subsets). For 3 months, patients adhered to their new diet. They were also provided health coaching for 6 months.²

“The diet we are researching is whole-food and plant-based. It’s basically vegan, with an additional emphasis on whole foods. We want patients to limit ultra-processed foods. But I tell them, ‘We’re looking for progress, not perfection,’” Francesca Castro, MS, RDN, CDN, dietician–nutritionist, Memorial Sloan Kettering (MSK) Cancer Center, said. “We understand that this is a big transition for people, and to commit 100% may not be feasible for everyone. I really try to emphasize that and let them know that we’re here to help support them and navigate the journey of transitioning to a whole-food, plant-based diet.”⁴

Over the course of a year, the trial found that people lost weight, had improved quality of life and metabolic markers (eg, cholesterol and insulin), and saw an improvement in biomarkers that measure the health of the immune system and microbiome. Additionally, 2 participants had improvement in their disease-progression trajectory. These findings were translated to Vk*MYC mice modeling the myeloma-precursor state, in which a high-fiber diet delayed disease progression through improved metabolism and microbiome composition leading to increased short-chain fatty acid production that reinvigorated antitumor immunity and inhibited tumor growth. The authors noted that these effects from fiber consumption were independent of calorie restriction and weight loss.^1,4

“There is existing evidence that a plant-based diet helps with weight loss, diabetes, cardiovascular disease, renal (kidney) disease, and possibly also autoimmune disease. So there are a lot of overall lifestyle benefits to a plant-based diet,” Urvi Shah, MD, myeloma specialist, MSK Cancer Center, explained. “There are many reasons to think that plant-based diets may affect MGUS and smoldering myeloma progression. For example, we know that the risk of these conditions increases in people with an elevated BMI. A person with an elevated BMI and MGUS or smoldering myeloma is twice as likely to progress to myeloma as a person with a normal BMI.”⁴

Above all, the authors emphasized that successful diet adherence is built on a philosophy of "progress, not perfection." Because transitioning to a whole-food, plant-based diet is a significant change, they acknowledged that committing 100% may not be feasible for everyone immediately. However, to improve adherence and ensure the diet is sustainable, they suggested patients consider gradual implementation of the diet, setting targeted goals, overcoming social challenges, and addressing misconceptions that they may have.⁴

REFERENCES

1. Shah UA, Cogrossi LL, Garces J, et al. A High-Fiber Plant-Based Diet in Myeloma Precursor Disorders – Results from the NUTRIVENTION Clinical Trial and Preclinical Vk*MYC Model. Cancer Discov. 2025; doi:10.1158/2159-8290.CD-25-1101

2. A Study of a Plant-Based Diet in People With Monoclonal Gammopathy of Undetermined Significance (MGUS) or Smoldering Multiple Myeloma (SMM). ClinicalTrials.gov identifier: NCT04920084. Updated September 9, 2025. Accessed December 22, 2025. https://clinicaltrials.gov/study/NCT04920084

3. Gerlach A. MRD, ctDNA Testing May Help Diagnose Multiple Myeloma Precursor Conditions. Pharmacy Times. December 4, 2025. Accessed December 22, 2025. https://www.pharmacytimes.com/view/mrd-ctdna-testing-may-help-diagnose-multiple-myeloma-precursor-conditions

4. Memorial Sloan Kettering Cancer Center. Diets for MGUS, Smoldering Myeloma, and Multiple Myeloma: Q&A With MSK Cancer and Nutrition Experts. News release. December 8, 2025. Accessed December 22, 2025. https://www.mskcc.org/news/diets-for-mgus-smoldering-myeloma-and-multiple-myeloma-q-with-msk-cancer-and-nutrition-experts