Dietary strategies for chemotherapy-induced nausea and vomiting: A systematic review

Background & aims: Chemotherapy-induced nausea and vomiting (CINV) is one of the most distressing cancer treatment side effects, affecting 20–70% of patients despite routine antiemetic prescription. Although dietary modifications are routinely recommended in clinical practice, there is lack of data synthesis to determine which dietary strategies for managing CINV are supported by quality evidence. This systematic review was conducted to examine the effect of dietary strategies on incidence and severity of CINV in adults compared with no intervention, usual care, or alternative strategies. Methods: Five electronic databases were searched from inception to 15th July 2021 for original research studies of interventional or observational design assessing dietary strategies for CINV. The quality of evidence was appraised, data were synthesized narratively, and Grading of Recommendations, Assessment, Development and Evaluations (GRADE) assessment of the certainty of the evidence was applied. Results: Twenty-one studies were included, 10 (48%) interventional studies and 11 (52%) observational studies. Most interventional and observational studies had a high or neutral risk of bias (70% and 72%, respectively). Of the interventions studied, strongest evidence with highest certainty was found for the very large positive effect of CINV-specific education and support with a personalized meal plan from a dietician, implemented in person or in writing, for reducing the severity of nausea and overall CINV (effect size: very large; GRADE: high). A statistically significant very large positive effect of ginger tea consumption was also found on overall CINV severity; however, certainty in this effect was very low. Although confidence in the findings from observational studies was very low to low, a statistically significant positive association was also found between a moderate intake of alcohol and incidence of nausea, vomiting, or overall CINV as well as nausea severity; the Mediterranean diet and nausea incidence and severity; and adequate intake of energy, protein, fat, or carbohydrate and nausea or vomiting incidence. Conclusion: Improved CINV was associated with CINV-specific nutrition education and support from health professionals. Non-restrictive dietary patterns that include adequate energy and macronutrient intakes, particularly protein, and include ginger, and Mediterranean diet concepts may benefit CINV; however, the confidence in the body of evidence to inform these conclusions is mostly very low to moderate. Future rigorous trials with adequate sample sizes, clearly defined dietary strategies, and valid outcome measures are warranted prior to dietary strategies being routinely prescribed alongside antiemetic regimens.