Evaluation of potential beneficial effects on airline flight crew member wellbeing after probiotic and antioxidant dietary supplementation

The life of airline crewmembers has been subjected to many changes in the past decades do to several reasons, such as: increase of flight frequency, flight time limitations and ultra-long range flight, the reduction of layovers and minimum rest time. In fact, this cohort undergos a wide and unique range of adverse job-related exposures such as cosmic ionizing radiation, circadian rhythm disruption due to night shift work and frequently crossing time zones, poor cabin air quality, elevated ozone levels, hypoxia, pesticides from cabin disinfection, high levels of occupational noise, heavy physical job demands, verbal and sexual harassment (McNeely et al. 2018a). Potential biological mechanisms may include induced release of stress hormones and indirect effects on sympathetic activity, which is associated with adverse metabolic outcomes (Correia et al. 2013). At the same time, the constant disruption of circadian rhythm, the highly irregular life style due to the 24hr rostering, the poor quality of food served on board of airlines and the high impact of temporary hypoxia on microflora’s well-being have increased the concern about the daily recommended dose needed of certain nutrients among flight crew. A dietary supplementation with probiotics and antioxidants could have a helpful and preventive action increasing the physiological defenses and enhancing the bowel habits among airline crewmembers. The aim of this in vivo study was to determine if daily consumption of a novel dietary supplement composed by SYNBIO® probiotics (1:1 mix of Lactobacillus rhamnosus IMC501® and Lactobacillus paracasei IMC502®) and elderberry extract, known for its antioxidant activity (Coman et al. 2017), may contribute to the well-being of on airline flight crew members. Forty consenting adults in good health currently employed by a major Italian Airline were enrolled in this single-centre, double blind, randomized, placebo-controlled study. Subjects were treated with one capsule/day of SYNBIO® probiotics-elderberry (PEG group) or placebo (PG) for 30 days. Bowel well-being (last 30 days record of intestinal regularity, stool volume, and secondary outcome measures following Silvi et al., 2014) health-related quality of life (Psychological General Well-Being Index - PGWBI) and gastrointestinal tolerance (Gastrointestinal Symptom Rating Scale - GSRS) were assessed asking the subjects to answer specific and validated questionnaires by self-evaluation. Saliva and faecal samples were collected before and after the period of dietary supplementation. Saliva was taken with a swab and processed using Human sIgA ELISA Kit in order to determinate sIgA levels; these represent the first line of defence from environmental factors and a reliable biomarkers to evaluate physiological stress. DNA extracted from stool samples was analysed using a Real-Time PCR with specific primers to quantify intestinal microbiota selected bacterial groups (Bacteroides-Prevotella-Porphyromonas spp., Staphylococcus spp., Clostridium coccoides-Eubacterium rectale group, Lactobacillus spp., Bifidobacterium spp. and Enterobacteriaceae). PEG subjects presented a statistically significant higher value (P<0.05) in the positive scale scores regarding constipation, showing a physiological improvement on those subjects initially affected by it. It has also been showed a statistically significant higher PGWBI global score in the PEG group compared to the PG one. Regarding the GSRS, the absence of intolerance to the supplementation treatment was proved by using 15 items revealing a median value of 1 (no discomfort), for each symptom in both PG and PEG group. In the PG group the maximum score assessed was 7 (very severe discomfort) instead in the PEG group the maximum score assessed was only 3 (mild discomfort), showing a potential preventive action of the probiotic/antioxidant supplementation. At the end of the study, the PEG subjects showed a remarkable increased presence of Lactobacillus spp. and Bifidobacterium spp. and an appreciable reduction of Enterobacteriaceae, even only after 30 days of supplementation, confirming the probiotics persistence capacity in the gastrointestinal tract and the direct antagonism and competitive exclusion effect provided by this supplementation. Concerning sIgA levels, the results showed a statistically significant difference (P<0.05) in the PEG group compared to the PG one at the end of the study. There was also a statistically significant difference (P<0.05) in the PEG group sIgA levels monitored during the 30 days supplementation. This study showed a significant difference on specific bacteria groups presence in subjects with probiotics-elderberry extract supplementation and the beneficial effect was established by the evidence of improved persistence of Lactobacillus spp. and Bifidobacterium spp., the absence of disconfort and any side effects during the study period. It was also detected an appreciable increase of the sIgA, confirming a strong physiological response by the immunity system of the supplemented subjects. The enhancement of body’s defence capacity and antioxidant activity due to the beneficial action of high-content polyphenols of the elderberry extract and the potential combination effect, indicating the ability of probiotics to increase the antioxidant activity of elderberry extract. In conclusion, the probiotics-elderberry extract supplementation tested in this study might be beneficial to airline crew members in increasing their overall physiological state, improving their immune defences and the strength and efficiency of their gastrointestinal tract against the stressful conditions due to their highly demanding working life. The combination of probiotics and elderberry extract proved to be safe and efficient providing a potential “starting point” for further scientific evaluation, involving a larger number of subjects for a longer period of time.