According to the study, which assessed probiotic supplementation among nurses for stress reduction and alleviation of viral illness, the environmental effects of a well-managed COVID-19 response by the country might have led to difficulty detecting differences between the intervention and placebo groups.
Initially, the objective of the study was to investigate whether supplementation with the probiotic Lactobacillus rhamnosus HN001 could reduce symptoms of stress and anxiety and improve psychological well-being in nurses working during the pandemic. On a deeper level, they also wanted to determine whether supplementation with the same probiotic could reduce the number of days participants experienced symptoms of a viral illness.
However, based on the results, the researchers encountered the challenge of controlling environmental factors – in this case, the COVID-19 pandemic – when conducting human trials during the disaster. It resulted in insignificant differences between the subject groups.
“Our results showed no significant difference in perceived stress or the average number of illness days between the probiotic-supplemented nurses and placebo group. Stress and viral illness symptoms reduced during the study for all participants, a trajectory likely influenced by societal-level factors. The powerful effect of well-managed public health response to the COVID-19 pandemic and the elimination of COVID-19 from the community in 2020 may have altered the trajectory of stress levels and reduced circulating viral infections, making it difficult to detect any effect of probiotic supplementation. Our study highlights the challenge in controlling environmental factors in human trials,” said the researchers.
The study, titled “A randomized trial of probiotic supplementation in nurses to reduce stress and viral illness” and published in the journal Scientific Reports, recruited 484 registered nurses working in a clinical environment anywhere in New Zealand. They were aged between 18 and 70, and enrolled between 2 July 2020 and 26 August 2020. Probiotic capsules containing Lactobacillus rhamnosus HN001 and identical placebo capsules were supplied by NZ dairy giant Fonterra. The nurses underwent randomisation and were instructed to take one capsule daily over 12 weeks.
Past research has shown that probiotics could manipulate the composition of the microbiota for improved health and prevent and treat mental health concerns like stress, anxiety and depression (Dinan, T. G. et al., 2013; Pirbaglou, M. et al., 2016; Lew L. C. et al., 2019). Specifically for the Lactobacillus rhamnosus HN001 strain, it could reduce postnatal depression and anxiety symptoms (Slykerman, R. F. et al., 2017).
The stress, anxiety, and psychological well-being between the probiotic and placebo groups were not significantly different in the current study. In addition, the scientists stated that it was not typical for nurses working during the pandemic in other countries. In fact, the stress and psychological well-being of the subjects improved from baseline to the end of the intervention period in their study.
There were no significant differences between the supplemented group and the placebo in terms of demographic factors and measures of psychological health at baseline. Change in stress, anxiety, and psychological well-being between baseline and the end of intervention also did not significantly differ between the groups.
Another salient finding was that the average number of days weekly that the nurses reported symptoms of cold or flu-like illness did not significantly differ between the groups. Moreover, the average number of illness days per week by intervention week for the probiotic and placebo groups showed a decrease in average illness days per week over the intervention period and graphically demonstrated that this decrease occurred in the placebo and probiotic groups.
“New Zealand was one of only a few countries to successfully eliminate COVID-19 in 2020 using lockdown measures and border controls. Following a strict government-led lockdown from 25 March to 13 May 2020, New Zealanders had relatively few restrictions on daily life, and there were no community cases of COVID-19. Confidence in government and public health measures to manage COVID19 and, therefore, fewer pressures in the health system than seen in other countries may be the reason for the observed improvement in the psychological health of nurses in this study.
“The powerful environmental effects of a well-managed COVID-19 response may have led to a pattern of decrease in stress that swamped any benefit of probiotics. Well-managed public health response to the COVID-19 pandemic is likely to have altered the trajectory of stress in this study population. Furthermore, fewer circulating viral illnesses during 2020 impacted the potential to detect a beneficial effect of probiotics on viral symptoms. These wider contextual events highlight one of the challenges of conducting intervention trials in human populations,” concluded the researchers.
Source: Scientific Reports
“A randomized trial of probiotic supplementation in nurses to reduce stress and viral illness”
Authors: Rebecca F. Slykerman and Eileen Li
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