Consuming a high-fiber diet after undergoing stem cell transplantation could help to reduce the risk of graft-versus-host disease (GVHD) by cultivating a healthy gut microbiome, according to studies conducted in patients and mice.
The findings add to a growing body of evidence highlighting the benefits of a high-fiber diet for maintaining microbiome health and suggest that dietary restrictions commonly recommended after a stem cell transplant – which typically result in low fiber intake – may be counterproductive for some patients.
“Our study reaffirms data [on the benefits of dietary fiber]that have been captured outside the GVHD world, and we’re now demonstrating that those ‘rules’ also apply to GVHD,” said Jenny Paredes, PhD, a staff scientist at the City of Hope National Medical Center in Duarte, California, and the study’s lead author.
“Significant decrease of fiber intake during transplantation is detrimental – it’s a lost opportunity to promote a healthy gut microbiome, recover from treatment-related microbiota injury, and protect against GVHD.”
GVHD is the most common complication of allogeneic stem cell transplantation, a procedure in which a person’s cancerous or abnormal blood stem cells are removed and replaced with healthy cells from a donor.
GVHD occurs when the donated cells attack the patient’s tissues and can cause various symptoms ranging from mild to life-threatening.
Because patients with GVHD often exhibit symptoms similar to irritable bowel disease (IBD) and the process of stem cell transplantation depletes the immune system, patients are encouraged to avoid eating raw vegetables and fruits without a removable peel for about 10 days before their procedure and 30 days after, when most patients stay in an isolation room in the hospital.
The goal of these dietary restrictions is to minimise their exposure to pathogenic bacteria and reduce IBD-like symptoms.
However, the cooked and processed foods most patients consume during this period tend to have lower fiber content, Dr. Paredes explained.
This can alter the makeup of the gut microbiome and deplete gut microbes that thrive through the fermentation of dietary fiber, a process that produces beneficial short-chain fatty acids linked with gut health and immunity.
To examine the potential benefits of maintaining high fiber intake during stem cell transplantation to avoid GVHD, the researchers worked in collaboration with investigators at Memorial Sloan Kettering Cancer Center to analyse the diets of 173 patients undergoing the procedure.
To measure fiber intake, they tracked all foods and beverages participants consumed and used food databases from the FDA to calculate the amount of fiber and other nutrients in their diets from 10 days before their transplant until 30 days afterward.
Dr. Paredes and her colleagues found that a low-fiber diet was linked with reduced gut microbiome diversity, which can also increase susceptibility to infection by intestinal pathogens.
They conversely found that a high-fiber diet was associated with better overall survival, reduced risk of acute GVHD affecting the lower gastrointestinal tract, and higher microbial diversity in the gut.
“The microbiome is protective if it’s in the right balance; if not, it could be a source of infection and increase the risk of mortality,” she said.
Patients with higher fiber intake also had higher levels of butyrate – a product of dietary fiber fermentation – and more gut microbes that produce butyrate. Previous studies have demonstrated that people with more butyrate producers in their gut are less likely to die from GVHD than those with lower levels of these microbes.
The researchers also studied the mechanisms involved in these effects through a companion study of GVHD and the dietary fiber source cellulose, a type of fiber that mammals cannot digest without the help of gut microbiota, in mouse models.
Mice fed a diet high in cellulose during stem cell transplantation 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.
According to Dr. Paredes, these findings bolster the evidence for the health benefits of butyrate and other products of fiber fermentation, including improved colon health, digestive support, and reduced inflammation.
Dr. Paredes cautioned that a high-fiber diet may not be best for all patients.
Since the process of fiber fermentation can lead to gas and bloating, reducing fiber intake can help alleviate discomfort if patients develop IBD-like symptoms.
Further study could help clarify the optimal way to increase fiber without triggering these symptoms.
Taken together, the findings suggest that plant-based, high-fiber foods could help to maintain a healthy gut microbiome and reduce the risk of GVHD, Dr. Paredes said.
She is now working to implement new nutrition protocols at the City of Hope and noted that hospitals can support patients undergoing stem cell transplantation by offering them diverse food choices.
“The more diverse our diet is, the more diverse our microbiome will be, and that applies to the clinic as well,” said Dr. Paredes.
Source: American Society of Hematology
