A high-fiber, plant-based diet may help delay the progression of precancerous plasma cell disorders into multiple myeloma, according to new research led by investigators at Memorial Sloan Kettering Cancer Center (MSKCC). The pilot clinical trial showed the dietary intervention improved body weight, metabolic health, and gut microbiome composition in patients with precursor conditions to multiple myeloma.
The findings were presented at NUTRITION 2025, the annual meeting of the American Society for Nutrition, held May 31–June 3 in Orlando, Florida.
“With cancers being detected earlier and precancerous states identified more frequently, there is a growing opportunity to understand how modifiable risk factors—like diet and lifestyle—affect cancer progression,” said presenting author Francesca Castro, a clinical research dietitian at MSKCC. “Our results highlight the importance of improved dietary quality in early disease states and could provide guidance for future clinical trials.”
Multiple myeloma is the second most common type of blood cancer and is typically preceded by non-malignant conditions such as monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). Previous studies have shown that high body mass index (BMI), poor diet, and gut microbiome imbalances are risk factors for progression from these precursor conditions to myeloma.
This research builds on earlier findings that link metabolic and immune factors to myeloma risk. Prior studies suggested that dietary interventions could modify these risk factors, but few clinical trials have been conducted to investigate this potential. The MSKCC team and collaborators sought to determine whether a structured high-fiber, plant-based dietary regimen could be safely implemented and sustained, and whether it would yield measurable health benefits.
“With everything that patients cannot control during and before cancer treatment, studying diet provides an opportunity for patients to make a difference in their disease risk and the potential success of their treatment,” said the study’s principal investigator Urvi A. Shah, MD, a physician-scientist at MSKCC. “Our study shows the power of nutrition in the preventative setting and showcases the potential to give patients a sense of agency in their diagnosis.”
The single-arm pilot study enrolled 20 patients with MGUS or SMM and a BMI of 25 or higher. Participants followed a high-fiber plant-based diet (HFPBD) for 12 weeks, combined with 24 weeks of individualized nutrition counseling. Participants were encouraged to eat until full but to limit their intake to whole plant-based foods such as fruits, vegetables, legumes, whole grains, nuts, and seeds. Animal products, added sugars, and highly processed foods were excluded from this diet.
Dietary intake data was collected through food logs and 3-day food records, which were analyzed using the online ASA24 dietary assessment tool. Adherence was measured as the percentage of calories from minimally processed plant-based foods. The primary endpoint was feasibility, assessed through dietary adherence and BMI change. Secondary outcomes included improvements in diet quality, insulin resistance, lipid profiles, inflammatory markers, and gut microbiome diversity.
According to the researchers, adherence rose from 20% of calories from high-fiber plant-based foods at baseline to 91% by week 12, while the median BMI dropped by 7%—a reduction that was sustained through the 52-week follow-up period.
Clinical markers also improved. Two patients showed a slowing in disease progression, while progression remained stable in the rest. The investigators observed meaningful changes in immune and metabolic responses, which they said could have implications beyond cancer.
“Our comprehensive analysis of improved immune and metabolic response suggests that a high-fiber plant-based diet can also reduce risk for cardiovascular conditions, diabetes and other metabolic conditions,” Shah said.
Based on these findings with a small patient cohort, the researchers are now enrolling participants in expanded NUTRIVENTION trials to study the effects of diet in larger cohorts and to compare whole food-based diets against fiber supplements. They also plan to investigate dietary interventions for other blood cancer precursors, such as clonal hematopoiesis.
“Think about what foods you can add or swap to increase fiber intake,” Castro said. “It can be very simple like adding a piece of fruit at the end of a meal or swapping out a refined grain for a whole grain. Eating more fiber can lower risk for many other conditions and can improve overall health, beyond just reducing cancer risk.”
