Can a low-bacterial diet improve outcomes for neutropenic cancer patients?

By Dr. Priyom Bose, Ph.D.Jul 20 2023Reviewed by Sophia Coveney

Scientists have reviewed the existing literature to provide evidence of the effectiveness of the low-bacterial diet (LBD) in reducing mortality rates, infection incidence, and improving the quality of life (QoL) in neutropenic cancer patients. This review is available in Nutrients.

Background

Cancer is one of the main causes of mortality worldwide. Although the risk of food-borne infections in patients with neutropenic cancer is managed using an LBD, the exact benefit is not well understood. 

Around 6.5% of cancer patients develop hematologic malignancies, which have been characterized by abnormal cell growth and development of blood cells (e.g., myeloma, leukemia, and lymphoma). 

Patients with hematologic malignancies are often subjected to aggressive treatment, such as radiotherapy, chemotherapy, and hematopoietic stem cell transplantation (hSCT). Although these therapies eliminate cancer cells, they also negatively affect the immune system of the patients causing severe bone marrow suppression.

Neutrophils are a type of white blood cell that defends the body against fungal and bacterial infection. Neutropenia is a condition that is characterized by a significant decrease in the number of neutrophils. 
Neutropenic cancer patients develop long-term neutropenia, making them susceptible to infections. Several preventive measures are used to protect patients with neutropenic cancer from infection. These patients are advised to use personal protective equipment (PPE), wear facemasks and improve hand hygiene, to reduce pathogen transmission. 

Dietary restrictions, such as LBD, are considered to be important preventive measures to control disease manifestation. LBD reduces the risk of food-borne infections by suppressing the exposure of harmful bacteria in the gut. 

The main concept behind LBD is that certain food when not adequately processed or consumed raw might contain pathogenic bacteria, such as Listeria, Salmonella, and Escherichia coli. For patients with neutropenia, exposure to these bacteria, even in small quantities, may cause severe infection.

LBD restricts the consumption of uncooked vegetables, fruits, meat, and fish. Additionally, it also restricts the consumption of soft cheese due to its higher risk of contamination. 
Even though not much evidence regarding the benefits of LBD for neutropenic cancer patients has been documented, this diet is commonly recommended to these patients. The practicality and necessity of implementing LBD are being evaluated in the scientific community.

It is imperative to better understand the advantages and limitations of LBD to design diets to best support neutropenic cancer patients. The current review assessed whether LBD impacts infection risks, mortality rates, and QoL in neutropenic cancer patients.

Study findings

Although a total of 1985 articles were identified through database searches, 12 studies fulfilled the eligibility criteria. These studies indicated that LBD imposes considerable limitations on various fresh food products (e.g., fruits, vegetables, meat, and fish). Two groups of patients, one following LBD and the other adhering to a free diet, exhibited similar rates of infection and mortality. 

Another study indicated that patients following LBD were at an increased risk of diarrhea and infection. In contrast, those following a free diet were found to be protected against common conditions including nausea, weight loss, and diarrhea.

A well-balanced diet, prepared with proper cooking techniques, storage, and handling methods, was able to minimize the risk of food-borne infections. A well-balanced free diet overcame the shortcomings of LBD and provided patients with a broader range of food choices. LBD affected the overall QoL of immunocompromised patients. 

Since many of these patients experience physical and psychological stress with reduced appetite and altered taste preferences, restrictions imposed through LBD significantly enhance their QoL.

Many patients subjected to cytotoxicity treatments experience malnutrition due to food aversion and malabsorption. These patients must be provided with optimal nutrients such that treatment-related complications can be minimized. A well-balanced nutritional diet supports an immunocompromised patient under cytotoxicity treatment with strength and enhances the recovery process.

Cooking methods associated with LBD such as boiling, soaking, and baking result in nutrient loss, particularly heat-sensitive minerals and vitamins. Since micronutrients play a key role in supporting immune function, they are particularly essential for immunocompromised patients. 

LBD restricts the consumption of fibers, which supports the gut microbiome. It is important to identify an optimal food program to support patients considering their cultural preferences and dietary traditions.

Limitations

The current review has several limitations including the study design and consideration of studies with different methodologies. Another drawback of the current study is the use of non-validated questionnaires with reduced response rates. 

Even though this study emphasized the importance of nutrition in QoL, a very limited number of studies considered in this review have addressed this aspect. The lack of a standardized definition of the LBD posed greater difficulty for the appropriate interpretation of the findings. 

Despite the limitations, the present review provided insight into the effects of LBD in patients with hematological malignancies at risk of developing neutropenia. This study highlighted the positive effects of a free diet over LBD for patients with hematological malignancies.