Abstract: In the original version of this review, we identified three RCTs that assessed different intervention and control diets in 192 participants (97 randomised to intervention diet; 95 to control diet) with different types of malignancies. For the update, we identified no eligible new studies. Co-interventions (e.g. protective environment, antimicrobial prophylaxis, central venous catheter care, oral care, hygiene practices, colony-stimulating factors) and outcome definitions also differed between studies. In all included studies, it was standard policy to give empirical antibiotics (and sometimes also antimycotics) to (some of) the participants diagnosed with an infection. Two studies included adults and one study included children. In all studies, only a scant description of treatment regimens was provided. All studies had methodological limitations. Pooling of results of included studies was not possible. In two individual studies, no statistically significant differences in infection rate were identified between intervention and control diets; another study showed no significant differences between treatment groups in the number of chemotherapy cycles with an infection. None of the studies mentioned infection-related mortality, but in one study, no significant difference in overall survival was observed between treatment groups. Time from onset of neutropenia to fever, duration of empirical antibiotics and antimycotics, diet acceptability (i.e. following the diet easily and following the diet throughout all chemotherapy cycles) and quality of life were all evaluated by only one study; for all outcomes, no statistically significant differences between treatment arms were identified. At the moment, no evidence from individual RCTs in children and adults with different malignancies underscores use of an LBD for prevention of infection and related outcomes. All studies differed with regard to co-interventions, outcome definitions and intervention and control diets. As pooling of results was not possible, and as all studies had serious methodological limitations, we could reach no definitive conclusions. It should be noted that 'no evidence of effect', as identified in this review, is not the same as 'evidence of no effect'. On the basis of currently available evidence, we are not able to provide recommendations for clinical practice. Additional high-quality research is needed.

Plain-language summary: Review authors identified three randomised studies comparing different diets in 192 children and adults with different types of cancer. Other interventions, such as antimicrobial prophylaxis (i.e. prevention of infection via antimicrobial therapy such as antibiotics) and hygiene practices, and definitions of study outcomes also differed between studies, and very limited information on anticancer treatment was given. All studies had methodological problems. Unfortunately, combining the results of included studies was not possible, but at the moment, no evidence from individual studies suggests that a low bacterial diet prevents infection. Data on survival, time from onset of neutropenia to start of fever, duration of empirical (i.e. start of treatment before determination of a definitive diagnosis) antibiotics and antimycotics (i.e. agents that target fungal infection), diet acceptability and quality of life all were evaluated by only one study; for all outcomes, no statistically significant differences between treatment groups were observed. None of the studies evaluated infection-related mortality. It should be noted that 'no evidence of effect', as identified in this review, is not the same as 'evidence of no effect'. No differences between diets were identified, possibly because few patients were included in these studies. On the basis of currently available evidence, the review authors were not able to give recommendations for clinical practice. Additional high-quality research is needed.