The Hype behind Expensive Probiotic Supplements
NEWS | 11 January 2026
This article was made possible by the support of Yakult and produced independently by Scientific American’s board of editors. There are microbes living in medicine cabinets across the U.S., next to the aspirin and the Band-Aids. And people want them there. Indeed, consumers probably paid good money for them. Probiotics are capsules or pills with live microorganisms—almost always bacteria or yeast—that are supposed to confer health benefits once people swallow them. Some of my friends, including a woman who was recently treated for cancer and a man with persistent digestive issues, bought the pills at the recommendation of doctors. Others, aware of a lot of new evidence about the ways microbes in our guts influence physical functioning, bought them on their own. Many hope the bacteria will improve their overall gut health, a desire reflected in bottle labels that say things like “improved digestion” and “clinically studied.” On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. But despite this popularity, evidence that probiotics help people is surprisingly limited. Medical organizations such as the American Gastroenterological Association (AGA) recommend only a few specific bacterial strains for a few well-defined conditions. “The average person likely doesn’t need probiotics and is unlikely to benefit from them for day-to-day use,” says gastroenterologist Omeed Alipour of the Santa Clara Health System in California, a spokesperson for the AGA. That cautious perspective is widely shared across the medical and scientific community, says Yosra Helmy, a veterinarian and microbiologist at the University of Kentucky, who studies the intersection of human and animal health. “It’s not because probiotics lack promise but because the science remains uneven, highly strain-specific and difficult to generalize,” she says. “Clearly, the marketing is ahead of the reality,” says gastroenterologist Neil Stollman, an associate clinical professor at the University of California, San Francisco. “The average person likely doesn’t need probiotics and is unlikely to benefit from them for day-to-day use.” —Omeed Alipour, gastroenterologist Another concern is that in the U.S., probiotics are dietary supplements, not medicines, and aren’t rigorously evaluated in the same way as pharmaceuticals. Probiotics are attractive because our gastrointestinal systems naturally contain trillions of microbes, collectively called the gut microbiome. Much of this microbiota—mainly bacteria but also yeast, fungi and viruses—is beneficial. It keeps the gut’s microbial community in balance and supports protective intestine and stomach linings. It also produces metabolites such as short-chain fatty acids that nourish cells, regulate immune system and metabolic balance, and help to produce vitamins. We regularly replenish our helpful gut bacteria when we eat yogurt and yogurt-based drinks, kefir, or other fermented foods such as kimchi, kombucha and miso. These are all natural sources of a wide variety of microorganisms. Fiber-rich diets provide fuel for the beneficial bugs once they are in our systems. In a few situations, diet alone is not enough, and that is when probiotic supplements come into play. Some of the strongest evidence in favor of added probiotics is for two rare conditions. One is necrotizing enterocolitis, which kills intestinal tissue in premature infants and can kill the babies, too. The other is pouchitis, inflammation of the small pouch created as part of surgery for ulcerative colitis or Crohn’s disease. Probiotics reduce the incidence of the first condition and ease the symptoms of the second one. For the wider population, a prevalent evidence-based reason to take probiotics is to prevent or minimize diarrhea brought on by antibiotics. That’s because antibiotics don’t target just the bad bacteria that give people the runs; they tend to wipe out entire colonies of helpful bacteria as well. (Chemotherapy has similar indiscriminate effects.) Studies show that some Lactobacillus and Bifidobacterium species, as well as a yeast called Saccharomyces boulardii, can help with antibiotic-induced problems. “All three of those have reasonable evidence that they lower your risk with antibiotics,” Stollman says. “You’ll probably feel better, and it probably won’t hurt you.” Studies have also found that probiotics reduce infections from the bacterium Clostridioides difficile, which can damage the colon. But the effect is small. Gastroenterologists recommend probiotics only for those at high risk of infection: people who are elderly, have had previous infections or are taking multiple antibiotics for long periods. Sufferers of irritable bowel syndrome (IBS) would love to find a probiotic that reduces symptoms such as bloating, constipation and diarrhea. Recent studies have found that some strains bring improvement for some people, but gastroenterologists can’t predict who will benefit and who will not. “It’s such a subjective marker to report symptom improvement on IBS, which itself is so broad,” Alipour says. As a result, there are no firm recommendations yet. Newer studies of so-called next-generation probiotics are underway. “The goal is to move from a one-size-fits-all supplement model toward precision microbiome interventions, where specific strains are matched to specific health problems,” Helmy says. These supplements might use a wider range of bacteria and improved encapsulation that is better able to withstand breakdown by the digestive system. Until those products are available, experts recommend that anyone looking to improve gut health begin with nutrition. A diet rich in fiber and fermented foods is a better solution than going to a store and buying a bottle of pills, Stollman says. For those who still want to try probiotics, the good news is that the risks are low overall. But their use should always be targeted and limited, Helmy says: try one for four to eight weeks and then reassess your symptoms. “They are not a universal solution,” she says.
Author: Josh Fischman. Lydia Denworth.
Source