Efficacy of Functional Foods, Beverages, and Supplements Claiming to Alleviate Air Travel Symptoms: Protocol for a Systematic Review

Background: Airline passengers often experience symptoms when travelling on long and ultra-long flights. These range from minor discomforts such as gastrointestinal symptoms to more serious life-threatening clinical conditions such as deep vein thrombosis. The food and supplement industry have responded with a plethora of products that claim to prevent one or more of the physiological or psychological symptoms associated with air travel. Objective: The aim of this literature review is to evaluate the efficacy of functional foods, beverages, and supplements that claim to address the unwanted effects of air travel in healthy adult populations. Methods: This research is a two-stage process. The first step is a scoping review of the functional foods, beverages, and supplements making claims that they lessen or prevent the physical or psychological symptoms associated with commercial air travel. Databases (ie, Medline, Embase, PsycINFO, and Web of Science), gray literature (ie, the flight catering magazines PAX International, APEX, and Onboard Hospitality), and search engines (ie, Google and Bing) will be used to identify products and generate a database. The second stage is a systematic literature review of the evidence supporting any health claims made for such products. The search will be conducted in Medline, Embase, PsycINFO, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Central Register of Controlled Trials. Additionally, gray literature that includes the reference list of studies included in the systematic literature review and scientific articles referenced by the products within our database will be hand searched. Randomized and nonrandomized controlled trials reporting on changes in flight-related physical or cognitive symptoms in healthy adults that were conducted in commercial flight or flight simulation settings will be included. Two authors will independently screen, extract data, and assess the strength of evidence and risk of bias of the studies. The strength of evidence will be judged using the Grading of Recommendations, Assessments, Developments, and Evaluations approach, and the risk of bias will be assessed using the appropriate Cochrane Collaboration tool (Risk of Bias for Randomized Control Trials II or Robins I for Nonrandomized Interventions). Results: The scoping review of available functional foods, beverages, and supplements was conducted from March 6, 2019, to August 31, 2019. The systematic literature review commenced on October 1, 2019. The review is expected to be completed in 2020. Conclusions: The review findings will help consumers and employees of commercial airlines make informed decisions on their use of functional foods and beverages for alleviating air travel-related symptoms.