Guest blog by Lillian Craggs-Dino, DHA, RDN, LDN, FASMBS-IH You've probably seen "probiotic" and "prebiotic" on yogurt cups, drink labels, and supplement bottles. If you've had metabolic and bariatric surgery, you're probably wondering: are they safe for me? Are they worth the money? Will they actually help my digestion? Here's what these terms mean, what the research shows so far, and how to think about adding prebiotics and probiotics to your diet after surgery. What Are Prebiotics and Probiotics Probiotics are live, helpful microorganisms that support the body when you get enough of them.1 Prebiotics, on the other hand, are parts of food your body can't digest. They feed the helpful microorganisms already living in your intestines, helping them grow and stay active.2 Foods or supplements that contain both are called synbiotics.3 How to Spot Probiotics on a Label Start with the ingredient list, or a panel labeled "live and active cultures." A helpful label names each organism in full: the genus, the species, and often a strain code, such as Lactobacillus rhamnosus GG. Vague wording like "contains probiotics" or "probiotic blend" doesn't tell you much, because the benefits found in research belong to specific strains rather than to probiotics in general. A yogurt cup, for instance, may list Lactobacillus acidophilus, Lactobacillus bulgaricus, and Streptococcus thermophilus. Next, look for the number of live organisms given in CFU (colony-forming units). The most useful labels tell you how many CFU remain through the end of the shelf life, not how many were added at the factory, so check the expiration date and any storage instructions too. Cultures are living things, and a product that needs refrigeration but has been sitting on a warm shelf may already have lost some of its count. Why Are Probiotics Good for You Probiotic microorganisms produce compounds such as lactic acid and hydrogen peroxide. Research suggests these compounds may help protect the lining of the intestines, and they have been studied for a possible role in managing digestive conditions, though results differ by strain and condition.4 Strains such as Lactobacillus casei, Bifidobacterium lactis, and Lactobacillus rhamnosus have been studied for a role in supporting the immune system.5 They "starve" the bad bacteria in the digestive tract, which may help keep things balanced. Other strains have been looked at for narrower uses. Lactobacillus rhamnosus and Lactobacillus salivarius have also been studied for a possible role in reducing gum disease (periodontal disease).6 Prebiotic and Probiotic Foods to Try Some natural foods act as prebiotics, which means they strengthen the good microorganisms you already have. If you have had metabolic and bariatric surgery, these foods are worth considering. They include onions, garlic, asparagus, bananas, apples, wheat bran, seaweed, green peas, and others.2 Butyric acid, a compound studied for gut health, is mainly produced when fiber is fermented by bacteria already living in your gut. A prebiotic fiber may be considered to better support gut health since it can be hard to consume enough daily fiber.7 A few foods are both prebiotic and probiotic, such as kombucha, natto, and fermented foods like kimchi and sauerkraut. If you have had bariatric surgery, you can also consider a probiotic supplement. A supplement with 5 to 10 billion CFU a day falls inside the range that studies have used depending on the strain and the reason for taking it.8 No one has settled on a single number that counts as "enough" CFUs, so your best guide is the dose that was actually tested for the strain in a product.1 And always talk with your health care provider before you start a new supplement. References Hill C et al. Nat Rev Gastroenterol Hepatol. 2014;11(8):506-514. Gibson GR et al. Nat Rev Gastroenterol Hepatol. 2017;14(8):491-502. Swanson KS et al. Nat Rev Gastroenterol Hepatol. 2020;17(11):687-701. Petrariu OA et al. Front Microbiol. 2024;14:1296447. Mazziotta C et al. Cells. 2023;12(1):184. Jayaram P et al. J Indian Soc Periodontol. 2016;20(5):488-495. Snodgrass JL et al. Int J Mol Sci. 2026;27(3):1289. Ouwehand AC. Benef Microbes. 2017;8(2):143-151.