How probiotics can help your immune system

By now, most of us have heard of probiotics: the live cultures in yogurt, kefir and some cheeses, and in fermented foods like miso, kimchi, tempeh and sauerkraut. They’re tasty additions to a diet, and they can support digestive health. But can they help your immune system too?

Probiotics are live microorganisms that are meant to have a health benefit when you eat them, and many are similar to the microbes that already live in your gut.³ Much of your immune system lives in and around the gut, which is one reason researchers have studied probiotics for infections.

Colds and respiratory infections

A Cochrane review of 23 trials with 6,950 children, adults and older adults found that people taking probiotics were less likely to get an upper respiratory infection like a cold, had slightly shorter episodes (by about a day), and were less likely to need antibiotics for them. The quality of the evidence was low to moderate, so the results are encouraging but not the final word.¹

When you take antibiotics

Antibiotics can be lifesaving, but they aren’t selective: they kill helpful bacteria along with harmful ones, and diarrhea is a common result. A 2025 Cochrane review of 47 trials with 15,260 people found that taking probiotics alongside antibiotics lowered the chance of antibiotic-associated diarrhea, and of diarrhea from C. difficile, a harder-to-treat gut infection.² If you’re prescribed antibiotics, ask your doctor whether a probiotic makes sense for you.

Not all probiotics are the same

Probiotics are strain-specific: a benefit shown for one strain doesn’t mean another strain will work the same way. Many probiotics are sold as dietary supplements, which don’t need FDA approval before they’re sold, so quality varies.³ Research is still sorting out which strains help with which conditions, including irritable bowel syndrome and inflammatory bowel disease.

Food first

You don’t need a pill to get probiotics. Many people who are lactose intolerant think they have to miss out because probiotics are so common in dairy. The good news is that fermented foods such as miso, kimchi, tempeh (fermented soy) and sauerkraut all add live cultures to your diet. Look for “live and active cultures” on yogurt and kefir, and choose refrigerated, unpasteurized sauerkraut and kimchi, since heat kills the cultures.

Who should be careful

Probiotics are generally safe for healthy people, but they aren’t for everyone. People with serious illnesses or weakened immune systems have a higher risk of harm, and severe infections have been reported in premature infants given probiotics.³ If you’re immunocompromised, critically ill or caring for a premature baby, talk with your doctor before using them.

Recovering from an illness or finishing a course of antibiotics? Adding fermented foods to your plate is an easy, enjoyable place to start.

This article is general education, not medical advice, and does not create a doctor–patient relationship. Talk with your own doctor before changing your diet, supplements or medications.

Sources

1. Zhao et al. (Cochrane Database of Systematic Reviews, 2022): Probiotics for preventing acute upper respiratory tract infections (23 trials, 6,950 participants)
2. Esmaeilinezhad et al. (Cochrane Database of Systematic Reviews, 2025): Probiotics for the prevention of Clostridioides difficile-associated diarrhea in adults and children (47 trials, 15,260 participants)
3. NIH National Center for Complementary and Integrative Health: Probiotics: Usefulness and Safety

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