New data suggest that a plant-based diet rich in fibre could help to improve the outlook for people with precursor conditions that can lead to multiple myeloma (MM).

The research, which involved a 12-week controlled diet with additional health coaching for 20 patients as well as experiments in mice, is the first interventional study to demonstrate that fiber-focused dietary modifications have the potential to slow the progression of blood cancers.  

MM is a cancer affecting plasma cells, a type of white blood cell.

It typically develops gradually starting with one of two precursor conditions known as monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM).

Since these conditions can last for many years without progressing to MM, researchers have sought ways to intercede and prevent patients with MGUS or SMM from developing cancer, but there is currently no cure for MM.  

“As we’re detecting cancers earlier – during the precancerous state – there is a greater opportunity to understand how lifestyle can modify the course of the disease and help patients live better,” said Urvi A. Shah, MD, principal investigator of the NUTRIVENTION trial and assistant attending physician at Memorial Sloan Kettering Cancer Center in New York.

“It is very anxiety-provoking when someone is told they have a precancerous state and there is nothing they can do. Our motivation is to see if we can empower patients to take steps to lower their risk.” 

People who are overweight face an increased risk of MM, and previous studies have suggested that factors such as diet and the health of the gut microbiome may influence disease progression.

Dr. Shah and her team conducted a pilot clinical trial involving 20 participants (median age of 62 years, 11 female and nine from underrepresented racial and ethnic populations) with MGUS or SMM and a body mass index of 25 or more to determine whether adopting a high-fibre, plant-based diet could be feasible and potentially slow disease progression.  

The trial lasted for one year.

During the first three months, participants received ready-made meals consisting of six lunches and dinners per week coupled with virtual nutritional coaching to help them adopt a diet rich in beans and legumes, whole grains, fruits, and vegetables, and avoid animal products and processed foods.

For the second three-month period, participants continued their nutritional coaching sessions but were responsible for preparing all of their own meals.

No meals or coaching sessions were provided for the remainder of the year.   

The trial met its primary endpoints for feasibility, with participants showing high adherence and significant weight loss.

The median overall adherence to the high-fibre, plant-based diet was 91% during the first three months and 58% at the end of the year, substantially higher than the 20% adherence rate before the study.

Participants lost a median of 7% of their body weight over the first three months and this was sustained throughout the course of the year.

Participants also showed improvements in quality of life and a variety of biochemical markers, including those related to insulin resistance, fecal microbiome diversity, and inflammation.  

“We saw improvements in all spheres, including metabolism, microbiome, and immune system markers, and we also saw that two patients with progressive disease had the progression stabilise and slow down on the intervention,” said Dr. Shah.

“Even though it’s just two cases, to our knowledge, it has not been shown before in an intervention setting that you can improve diet and lifestyle and actually slow or change trajectory of the disease.” 

Researchers at the Bellone laboratory at IRCSS San Rafaele Hospital in Milan, Italy conducted a similar experiment on SMM in a mouse model.

In the mice, consuming a high-fibre diet delayed the progression to MM from a median of 12 weeks among those fed a normal diet to 30 weeks among those fed a high-fibre diet.

All mice in the control arm developed MM during the study, while 40% of those fed a high-fibre diet did not.  

“Mechanistically, we saw that the beneficial effects of a high-fibre diet were similar in overweight and lean mice even in more advanced phases of the disease,” said Dr. Shah.

“Efficacy of the diet also appears independent from calorie intake and was not just a matter of how much body weight was lost.”

Biochemical analyses pointed to increased microbial diversity and particular substances produced by gut microbes as potential mechanisms for slowing disease progression by slowing the growth of abnormal plasma cells, reducing inflammation, and improving immune functioning.  

Researchers cautioned that findings in mice do not necessarily translate to humans and that the clinical trial was limited by its small size, making it challenging to understand why some participants saw a change in their disease progression while others did not.

A follow-up study is now underway to investigate the potential impacts of dietary changes and/or dietary supplements on the progression to MM in a larger patient group.   

This research was supported by funding from the American Society of Hematology, the National Cancer Institute, the Allen Foundation Inc, the Paula and Rodger Riney Foundation, the Solomon Fund, the AIRC Foundation for Cancer Research, and the Leukemia and Lymphoma Society.  

Source: American Society of Hematology