For decades, patients undergoing blood cancer treatment have been told to avoid certain foods to reduce infection risk, guidance that some physicians hoped could safely be relaxed. Now, a University of Florida study offers clear evidence that a diet designed to limit exposure to foodborne microbes results in fewer serious infections, confirming it is still the safest choice.
The findings come at a time when some clinicians have questioned whether the diet, which prohibits raw fruits and vegetables, unpasteurized dairy and undercooked animal proteins during intensive cancer therapies, was overly restrictive and could contribute to poor nutrition, said co-lead author Dr. John Wingard, a professor emeritus of medicine at the UF College of Medicine.
“Recently, some doctors have questioned whether a more liberal diet could safely be encouraged, especially since it might make eating easier, more enjoyable and, hopefully, improve nutrition among patients,” Wingard said.
Published in the Journal of Clinical Oncology, findings from the large phase 3 randomized trial — considered the gold standard for clinical trials — demonstrated that patients hospitalized for blood cancer treatment who followed a diet restricting fresh fruits and vegetables had a lower risk of developing serious infection. The researchers stopped the trial early to safeguard patient safety.
“Given the evidence from this study, we cannot change the current standard of care,” said co-lead author Dr. Ji-Hyun Lee, a professor of biostatistics in the UF College of Public Health and Health Professions and associate director for Cancer Quantitative Sciences at the UF Health Cancer Institute. “This study provides truly critical information for patients who are vulnerable to infection.”
The “neutropenic” diet, gets its name from neutropenia, a condition in which patients have low levels of protective white blood cells called neutrophils. During chemotherapy, these cells are suppressed, increasing infection risk. The most serious infections arise from the intestinal tract and are linked to microbes in uncooked foods. Fresh fruits and vegetables are important components of a healthy diet once patients’ immune systems have recovered, but during treatment, clinicians prescribe the diet to protect against infection.
When the neutropenic diet was introduced more than a half-century ago, it was not tested in a randomized trial. While a few smaller studies have evaluated the diet, UF’s study is the largest and most rigorous.
For the study, more than 200 patients with blood cancer who were hospitalized during chemotherapy or while receiving a stem cell transplant were randomly assigned the neutropenic diet or a more liberal diet that encouraged patients to eat at least one serving of fresh fruits and/or vegetables a day. Patients on the liberal diet were also permitted to eat pasteurized yogurt.
Nurses and dietitians measured patients’ consumption of hospital food and beverages, oral supplements, other foods not provided by the hospital, and all fresh fruits and vegetables. Dr. Wendy Dahl, a professor of nutritional sciences in the UF College of Agricultural and Life Sciences, oversaw the trial’s nutritional assessments.
To ensure quality of study data that is typically difficult to collect — everything a patient eats and drinks for weeks — the research team built a web-based platform that allowed them to monitor data collection on a weekly basis, an approach pioneered at the UF Health Cancer Institute under Lee’s direction. Real-time checks helped the data scientists on the team, including Derek Li, a UF Ph.D. student in biostatistics and study co-author, spot patterns early and quickly identify missing information.
Before the trial, the team established an acceptable threshold for the difference in infection rates between the two diets. Researchers halted the study once the findings showed that those on the liberal diet were more likely to experience a major infection than those on the neutropenic diet.
The study finally answers a decades-old question about the effectiveness of the neutropenic diet at preventing infection, but more work needs to be done to address ongoing nutrition issues, the UF researchers said. The study found that hospitalized patients in both diet groups did not consume enough calories for good nutrition, a common issue that may be attributed to treatment side effects, including nausea and appetite loss.
“We still need to come up with better approaches to improve the nutrition of these patients without compromising their safety,” Wingard said. “We recognize how important good nutrition is for the gut microbiome and patient outcomes.”
Funding for the study was provided by the UF Health Cancer Institute, the Gatorade Trust through a grant by the UF College of Medicine, and the Price Eminent Scholar endowment.