A person reading recent popular press articles could easily be left with the impression that probiotics have no value to you if you’re healthy (see here, here, here, here, here and here). This last article, by the well-respected Scientific American, states “Although certain bacteria help treat some gut disorders, they have no known benefits for healthy people.”
It’s a bit frustrating to read these articles, because it seems that the experts that are interviewed just don’t know the evidence. But they have all the credentials to be convincing, so their incorrect assessments of the evidence go unchallenged.
This prompted the International Scientific Association for Probiotics and Prebiotics (ISAPP) to develop a consumer-friendly infographic on this topic, Probiotics for Healthy People. Check it out. By their nature, infographics are simple, so here is a bit of additional perspective as an accompaniment.
Let’s consider the evidence. One meta-analysis, conducted by the Cochrane group, considered the impact of probiotics on the prevention of upper respiratory tract infections (URTIs). They extracted data from 12 randomized, controlled trials involving 3720 subjects of all ages. Although the overall quality of the evidence was generally low, they found that probiotics reduced episodes, duration of an episode and antibiotic prescriptions for URTIs. “Probiotics were found to be better than placebo in reducing the number of participants experiencing episodes of acute URTI by about 47% and the duration of an episode of acute URTI by about 1.89 days.”
Some critics might acknowledge there may be some benefit, but contend that the magnitude of effect is so small as to be meaningless. Consider, however, that the popular drug Tamiflu was shown in a 2014 meta-analysis to reduce symptom duration by approximately 1 day, a magnitude of effect that was apparently significant enough to secure FDA drug approval. Probiotics shortened duration of URTIs by over 1.5 days.
Another contributor to the perpetuation of the idea that probiotics have no benefit for healthy people comes from a 2016 study by Kristensen et al., who concluded there was no impact of probiotics on gut microbiota composition. Unfortunately, this was interpreted by some to mean that there is no impact of probiotics on healthy people. They conflated an impact on microbiota with an impact on health.
So what other benefits might probiotics bestow on reasonably healthy people? ISAPP is careful to state that these benefits should be considered strain-specific, unless accumulated evidence suggests otherwise. But here’s a list (adapted from here and here). You can decide for yourself if the benefits are worth the investment.
- Reduce incidence or duration of common respiratory tract infections
- Improve blood lipid profiles in people with mildly elevated lipid levels
- Improve digestion of lactose in lactose malabsorbers
- Help improve immune function, both with decreasing incidence of atopic dermatitis in infants and inhibiting pathogens
- Support an effective gut barrier
- Decrease vaginal and urinary tract infections
- Reduce crying time in colicky babies
- Manage mild digestive symptoms or intestinal regularity
- Reduce postpartum depression scores (see here)
- Reduce sad mood and anxiety (see here)
- Reduce antibiotic-associated side effects. Lest you object that antibiotics are not used in healthy people, remember that many of us carry on with normal lives while on antibiotics. For example, prophylactic use during dental procedures for those with joint replacements, or to treat ear or sinus infections.