High-fiber diet cuts risk of rejected bone marrow and stem cell transplants, cancer research discovers

Scientists and physicians with the US-based cancer research and treatment organization City of Hope are presenting new research on high-fiber dietary interventions for bone marrow and stem cell transplant patients at risk for graft-versus-host-disease (GVHD) and myeloma at this year’s ongoing American Society of Hematology conference (December 7–10) in San Diego, California, US.

One featured study led by Jenny Paredes, Ph.D., City of Hope staff scientist, suggests that consuming a high-fiber diet after transplantation could reduce the risk of developing GVHD by supporting a healthy gut microbiome.

During GVHD, donated cells attack the patient’s own tissues and can cause a variety of symptoms ranging from mild to life-threatening.

“While high-fiber diets may not be appropriate for everyone, this study shows the exciting potential for high fiber to play a role in reducing GVHD risk in transplant patients,” says Dr. Paredes.

“We look forward to designing a nutritional intervention for clinics that can help diversify the gut microbiome through food choice and improve outcomes for people receiving bone marrow or stem cell transplants.”

Cutting GVHD risk with high-fiber diet

When patients undergo a bone marrow or stem cell transplant from a donor for blood cancer treatment, they run the risk of developing GVHD, the most common complication from the procedure.

“We’ve known that dietary fiber plays a beneficial role in regulating the immune system via the gut in healthy populations,” says Dr. Paredes. “Our work now shows this may be true for transplant patients, too, and that dietary restrictions post-procedure that might result in low fiber intake could be counterproductive.”

Patients with GVHD, who have similar symptoms to people with irritable bowel syndrome and a depleted immune system, are often advised to refrain from eating raw vegetables and strawberries, blueberries and other fruits without a removable peel for about 40 days after transplantation.

The low-fiber diet, which includes more cooked foods, can reduce a patient’s exposure to harmful bacteria and reduce symptoms, suggests City of Hope.

By analyzing the diets of 173 patients undergoing transplantation — from 10 days before the procedure until 30 days after — Dr. Paredes and a team of researchers found that a high-fiber diet was associated with a reduced risk of acute GVHD in the lower gastrointestinal tract and better overall survival. A low-fiber diet was linked with less diversity in the gut microbiome, which can make people vulnerable to infection.

The researchers also found that patients with higher fiber intake had higher levels of gut microbes that produce butyrate, a product of dietary fiber fermentation which has been shown in previous studies to protect against GVHD.

Mouse model study

To investigate the mechanisms involved in these effects further, Dr. Paredes and her collaborators also conducted a preclinical companion study using mouse models of GVHD.

After receiving a stem cell transplant, mice fed with a high-fiber diet of cellulose, which cannot be digested without the help of gut microbiota, had a reduced rate of death from GVHD and other markers of reduced GVHD risk, as well as higher microbial diversity and butyrate concentrations in the gut.

“While high-fiber diets may not be appropriate for everyone, this study shows the exciting potential for high fiber to play a role in reducing GVHD risk in transplant patients,” says Dr. Paredes.

The study, done in collaboration with investigators at Memorial Sloan Kettering Cancer Center, was supported by funding from the National Cancer Institute and private foundations.

Plant-based diet may delay disease progression

Diet and obesity are known to play a role in many diseases. But for people with monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) — two precursors to the blood cancer myeloma — poor diet quality low in plant foods and elevated body mass index (BMI), along with insulin resistance and inflammation, have been implicated in the progression of precursor plasma cell disorders to cancer.

To test whether a nutritional intervention consisting of a high-fiber, plant-based diet could impact these modifiable risk factors and delay the onset of cancer, a team of researchers enrolled 20 participants with MGUS or SMM and an elevated BMI in a pilot study.

Participants received a controlled diet for 12 weeks and health coaching for 24 weeks.

Urvi Shah, M.D., M.S., of Memorial Sloan Kettering Cancer Center, the trial’s principal investigator, will present the study at the American Society of Hematology conference.

“We saw an improvement for many risk factors, including weight loss, reduced insulin resistance, better microbiome profiles and decreased inflammation,” says Dr. Van den Brink, the study’s senior author.

The intervention was “safe, feasible and improved quality of life” for participants, two of whom were observed to have an improvement that slowed the trajectory of long-term disease progression.

Additional studies by collaborators with the Laboratory of Microbiology at IRCCS Ospedale in San Raffaele, Milano, Italy, and done in SMM mouse models who were fed high-fiber diets or standard diets, found that the nutritional intervention delayed progression to myeloma.

Notably, 44% of mice in the interventional arm did not progress to myeloma during the study period, whereas all mice in the standard diet arm did progress.

“This is the first interventional clinical trial to show that plant-based, high-fiber diets can have a beneficial effect in delaying the progression of a blood cancer,” says Dr. Van den Brink. “Our findings support further research into the role nutrition can play in changing the body’s immune response for patients with plasma cell disorders.”