Probiotics have been in the wellness spotlight for some time—all thanks to their gut health benefits. But now, companies are selling the popular supplement with other health benefits beyond keeping you regular. During peak cold and flu season (aka right now), you may see more claims about probiotics for immune system support. But can probiotics truly help boost your immune system and help your body fight off illnesses like the common cold?
Experts in This Article
a microbiologist and the VP of Health and Scientific Affairs at Danone North America
According to the International Scientific Association for Probiotics and Prebiotics, probiotics are live microorganisms that, when taken in specific amounts, provide certain health benefits. They are considered “good” bacteria that can help stop the overgrowth of “bad” bacteria in the gut and produce beneficial compounds like short-chain fatty acids1 (i.e., acids in the gut that can help regulate metabolism, inflammation, and disease). Some studies have even found that probiotics may be linked to helping absorb vitamins2, reinforce the gut barrier3, and neutralize toxins4. Essentially, it’s well-documented that probiotics are good for your gut.
But can these good bacteria help with immune system function, too? Here, we spoke with Miguel Freitas, PhD, a nutrition scientist, vice president of health and scientific affairs at Danone North America, and one of the world’s leading experts on the complex interactions between probiotics, the gut, and the microbiota, to find out.
So, can probiotics strengthen your immune system?
Dr. Freitas says when considering probiotics for immune system support, it’s important to understand that the benefits of probiotics will largely depend on the strain you take. Meaning not all probiotics have the same health benefits. While one may work against bloating, another may be more effective at relieving constipation, for instance.
Some research5 suggests certain probiotic strains could help your immune system, but the exact way these strains work to support immunity is an area of ongoing study, Dr. Freitas says. So far, “it has been proposed the probiotics can interact directly with intestinal immune cells or produce certain substances that serve as mediators of this cross-talk (i.e., the communication between probiotics and immune cells in the gut.),” he adds. However, this is just a theory, and experts still have much to learn about the possible connection.
Beyond working directly with immune cells in your gut, studies have found probiotics may potentially enhance your immunity6 in other ways, including:
- Producing substances that kill harmful microorganisms.
- Competing with harmful microorganisms and toxins for adherence to the gut wall, which prevents them from taking hold in the gut.
- Promoting survival of intestinal cells.
- Enhancing gut barrier function7 (i.e., how strong and healthy the gut lining is).
- Stimulating protective responses from intestinal cells toward foreign substances.
- Enhancing innate immunity (the body’s first response to harmful, foreign substances).
- Influencing harmful microorganism-induced inflammation via immune cell signaling pathways.
The gut and immune system are highly connected
“Many are surprised to learn that 70 percent of our immune system is located in our gut,” shares Dr. Freitas. But it’s true: Along with the trillions of microbes that live in our digestive tract, so do immune cells that help us fight off foreign bacteria and viruses that can make us sick. It stands to reason, then, that prioritizing your gut health (and balancing the good and bad bacteria that live within it) could also help support your immune system and the other microbiomes in your body—including your skin, oral, and vaginal microbiome.
Bottom line? Taking probiotics will not completely safeguard you from catching colds or the flu, but it may help support your immune system as it’s hard at work fighting off illness. “The more we can learn about the gut microbiome, the more we can leverage it to benefit health,” Dr. Freitas adds.
What is the best type of probiotic strain to take for immune health?
“Because probiotic benefits are strain-specific, you’ll want to look for a product that contains a strain of bacteria clinically shown to support the immune system,” says Dr. Freitas. One example of a probiotic commonly studied and shown to be associated with immune function is Lactobacillus casei DN-114 001—a strain found in products such as DanActive Probiotic Dailies yogurt drinks ($5). You can also find probiotic supplements with this specific strain, but ask your healthcare provider about whether they’re right for you before trying them. They can recommend specific brands that contain quality ingredients and are third-party tested.
As far as dosage, Dr. Freitas says the amount of colony-forming units (CFUs)—the unit of measurement for probiotics—needed for any particular benefit will depend on the probiotic strain, including what amounts have previously been studied in clinical trials. While the recommended dosage can range from 100 million to over a trillion CFUs per day, most probiotic strains have been studied for use between one and 10 billion CFUs daily.
Other ways to support your immune system
While certain probiotics may help support your immune system, there are other ways to keep your immune health in tip-top shape. Here are some strategies to try:
1. Eat colorful fruits and veggies
“There isn’t one single food or nutrient that will magically “boost” your immune system, but eating an array of colorful fruits and vegetables can help give your body what it needs to keep your immune system working at its best—like vitamins C, D, and A, and minerals like zinc,” says Dr. Freitas.
2. Get daily physical activity
According to Dr. Freitas, emerging evidence suggests that physical activity could benefit your immune system. For adults, it’s recommended to get at least 150 minutes of moderate-intensity exercise, as well as two days of muscle-strengthening exercise per week. And remember: You don’t have to get all 150 minutes in one go. Most people prefer to split up their workout time throughout the week, like doing 30 minutes of activity five days per week.
3. Reduce alcohol intake
While the occasional cocktail or glass of wine isn’t likely to negatively affect your immune system, excessive alcohol use may lead to a weakened immune system and increase your chances of getting sick. If you’re looking to cut back, consider trying out a mocktail a few nights per week or practicing mindful drinking habits to reduce your intake in general.
4. Prioritize getting a good night’s sleep
Just as getting enough exercise is important for a healthy immune system, so is getting plenty of high-quality sleep, says Dr. Freitas. In fact, “research suggests that those with poor sleep habits are more likely to get sick when exposed to viruses like the ones that cause the common cold,” he adds. To reap all the physical and mental health benefits of proper zzzs, aim to get anywhere from 7 to 9 hours of sleep per night, and try to go to sleep and wake up around the same times every day.
5. Visit your healthcare provider
If you feel like you’re always getting sick, or you already know that you are immunocompromised (i.e., you have a weak immune system due to chronic illness, certain medications, etc.), it’s worth checking in with your healthcare provider to see if there’s something more going on. They can request bloodwork and other diagnostic tests to determine the root cause of your frequent illness and offer treatment geared toward protecting your immune system.
The final takeaway
While emerging evidence indicates that certain probiotics may support your immune system (by interacting with immune cells in the gut and preventing “bad” bacteria from taking over), researchers still have a lot to learn about the exact role that probiotics play in immune health. Also, no guarantee taking probiotic supplements will prevent you from catching illnesses like a cold or the flu.
That said if you’re looking to try probiotics for both gut health and immunity, make sure the supplement contains the Lactobacillus casei DN-114 001 strain, which has been shown to help support immune health, per Dr. Freitas. Make sure you’re also purchasing supplements that are third-party tested for quality by organizations like the USP or NSF or ones that are recommended by your healthcare provider.
Ultimately, keeping up with other lifestyle habits that support immunity—like reducing alcohol intake, prioritizing sleep, and getting exercise—will increase your chances of fighting off germs this cold and flu season.
Tan, Jian et al. “The role of short-chain fatty acids in health and disease.” Advances in immunology vol. 121 (2014): 91-119. doi:10.1016/B978-0-12-800100-4.00003-9
↩︎Nysten, Jana, and Patrick Van Dijck. “Can we microbe-manage our vitamin acquisition for better health?.” PLoS pathogens vol. 19,5 e1011361. 18 May. 2023, doi:10.1371/journal.ppat.1011361
↩︎DiMattia, Zachary, et al. “Effect of probiotic supplementation on intestinal permeability in overweight and obesity: A systematic review of randomized controlled trials and Animal Studies.” Advances in Nutrition, vol. 15, no. 1, Jan. 2024, p. 100162, https://doi.org/10.1016/j.advnut.2023.100162.
↩︎Baralić, Katarina, et al. “Probiotic cultures as a potential protective strategy against the toxicity of environmentally relevant chemicals: State-of-the-art knowledge.” Food and Chemical Toxicology, vol. 172, Feb. 2023, p. 113582, https://doi.org/10.1016/j.fct.2022.113582.
↩︎Hill, C., Guarner, F., Reid, G. et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol 11, 506–514 (2014). https://doi.org/10.1038/nrgastro.2014.66
↩︎Yan, Fang, and D B Polk. “Probiotics and immune health.” Current opinion in gastroenterology vol. 27,6 (2011): 496-501. doi:10.1097/MOG.0b013e32834baa4d
↩︎Assimakopoulos, Stelios F et al. “The Role of the Gut Barrier Function in Health and Disease.” Gastroenterology research vol. 11,4 (2018): 261-263. doi:10.14740/gr1053w
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