Even if some of the bacteria in a probiotic managed to survive and propagate in the intestine, there would likely be far too few of them to dramatically alter the overall composition of one's internal ecosystem. Whereas the human gut contains tens of trillions of bacteria, there are only between 100 million and a few hundred billion bacteria in a typical serving of yogurt or a microbe-filled pill. Last year a team of scientists at the University of Copenhagen published a review of seven randomized, placebo-controlled trials (the most scientifically rigorous types of studies researchers know how to conduct) investigating whether probiotic supplements—including biscuits, milk-based drinks and capsules—change the diversity of bacteria in fecal samples. Only one study—of 34 healthy volunteers—found a statistically significant change, and there was no indication that it provided a clinical benefit. “A probiotic is still just a drop in a bucket,” says Shira Doron, an infectious disease expert at Tufts Medical Center. “The gut always has orders of magnitude more microbes.”
The statements on this website have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease. The contents of this website are not medical advice and are intended for general knowledge and informational purposes only. Probiotics support many facets of overall health when taken regularly as part of a balanced diet and healthy lifestyle.
Previous studies have investigated the use of probiotics — those healthy gut bacteria — by testing their impact in guts already affected by disease, the researchers wrote in the study. For the new investigation, they wanted to see how a probiotic would impact SCFA production in a healthy gut. They chose to work with baby poop because infants' gut microbiomes are typically free from age-related diseases "such as diabetes and cancer," and because of the sheer abundance of infant feces at their disposal. ("Their poop is readily available," Yadav said.)
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But before you start reaching for the calcium supplements, there may be a more effective way to support your bone health. Like many other parts of the body, the health of your bones is closely tied to the health of your gut, especially your intestines. Temporary intestinal inflammation can trigger an immune response in which your body releases interleukins, proteins that have an immune function but also absorb bone tissue. If the temporary inflammation remains unaddressed, these molecules can take a toll on your bones, eventually weakening them.14
Officials in the E.U., where supplements are more heavily regulated than in the U.S., haven't authorized the use of the word probiotic to back any health claim. The only approved use related to microorganisms is "live yogurt cultures and improved lactose digestion." It can all feel like, well, a punch to the gut. So we asked scientists at the forefront of probiotic research to help us separate fact from hype, and pros...from cons. Here's what you need to know.
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Previous studies have been contradictory, with some yielding more positive results about the benefits of probiotics, but most of them looked at probiotics in stool samples, not directly in the gut itself. In the new research, the scientists used more invasive methods to take samples of gut bacteria directly from different areas of the digestive system.