When most people think about probiotics, they focus on digestive problems. That’s only natural, since these beneficial bacteria are expected to act by influencing the gut microbiome (Nature Medicine, May 2019). However, a new analysis suggests that people who take probiotics are less likely to lose work time from flu-like illness (Frontiers in Pharmacology, Aug. 28, 2019).
What Is Flu-Like Illness?
People with a respiratory tract infection causing cough and fever that started 10 days ago or less have a flu-like illness. If they see a health care professional and undergo an antigen test for influenza, that diagnosis could change. The test provides a definitive diagnosis of flu. Most respiratory tract infections that keep people out of work or school are never diagnosed as flu, though. Probably the vast majority are caused by some other non-influenza virus.
How Do Probiotics Affect Respiratory Tract Infections?
Analysts noted the results of two different meta-analyses. One, conducted by the independent researchers of the Cochrane Collaboration, concluded that: “probiotics may be more beneficial than placebo for preventing acute URTIs” (Cochrane Database of Systematic Reviews, Feb. 3, 2015). The investigators lamented the inadequate quality of the research, however.
The second meta-analysis considered 20 randomized controlled trials of probiotics on respiratory infections (British Journal of Nutrition, July 14, 2014).
Much like the Cochrane scientists, these investigators concluded:
“This systematic review provides evidence from a number of good-quality RCT that probiotics reduce the duration of illness in otherwise healthy children and adults.”
The Economic Impact of Flu-Like Illness:
The analysts used the results of these meta-analysis to create computer models for how many fewer Americans would see health care providers, get antibiotic prescriptions and miss work due to flu-like illness. Never mind that antibiotics are not effective against such viral infections–many people get prescriptions anyway. With the use of probiotics linked to fewer upper respiratory tract infections, fewer doctor visits and a lower use of antibiotics, the authors estimated the savings to the U.S. economy at over $1 billion. They reported that side effects of probiotics were uncommon and minor, except for digestive complaints.
The only problem: we don’t know which probiotic species and strains are most cost-effective. One thing we do know: probiotics do not speed recovery from antibiotics. You can learn more about this by listening to our interview with investigator Eran Elinav in Show 1159.