“Probiotics prevent colds.”
Probiotics do not reliably prevent colds: in trials, somewhat fewer people taking them got colds, but the evidence is weak and the true benefit is likely smaller.
Probiotics are not a dependable shield against colds. Trials suggest a modest benefit at best, and no single product has strong proof, so a probiotic is optional, not something you need for cold season.
Skip buying a probiotic just to avoid colds; if you already take one for another reason, you do not need a second product for colds.
Safety note: Side effects are usually minor in healthy people, but harmful effects are more likely in people who are very ill or have weak immune systems. Severe or fatal infections have been reported in premature infants given probiotics, and the FDA has warned health care providers about this risk.
Talk to a healthcare professional if: you are seriously ill or have a weakened immune system, or you are thinking about giving a probiotic to a premature baby.
Pooled trials point to somewhat fewer colds with probiotics, but the reviewers rated that evidence low certainty because many trials had unclear methods, results looked skewed toward positive studies, and industry-funded trials were more likely to find a benefit. The trials also used many different strains, so no single product has strong proof.
Probiotics do not reliably prevent colds: in trials, somewhat fewer people taking them got colds, but the evidence is weak and the true benefit is likely smaller. In a 2022 Cochrane review, about 34 in 100 people taking probiotics had at least one cold or similar infection during the trials, compared with about 45 in 100 on placebo, a low-certainty result.
The review pooled 23 trials with 6,950 children, adults and older adults, mostly using one or two strains of bacteria for more than three months. Fewer people on probiotics had three or more infections, and fewer needed antibiotics for them (both moderate certainty). Colds were about 1.2 days shorter on average (low certainty). The reviewers noted that trials funded by industry, or run by authors with financial ties, were more likely to report a benefit, and the pattern of results suggested missing negative studies. Because each trial tested its own product, the pooled result does not show that any particular probiotic works. Side effects were minor, mostly stomach symptoms such as gas and diarrhea, and were no more common than with placebo.
- Zhao Y, Dong BR, Hao Q. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database of Systematic Reviews. 2022;8(8):CD006895. DOI: 10.1002/14651858.CD006895.pub4. PMID: 36001877. PMCID: PMC9400717
- National Center for Complementary and Integrative Health. Probiotics: Usefulness and Safety. Last updated August 2019