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Millions of friendly bacteria live in our intestines. They’re essential to digestion. But diarrhea can throw off the balance of these microbes in your gut. Probiotics, doses of helpful bacteria or yeasts, may help get things back on track and treat some kinds of diarrhea, studies suggest.

One source of probiotics you might know about is yogurt, which is made by adding bacteria to milk. The same microbes may help keep your intestines healthy. There are dozens of other kinds that may have health benefits, too.

Not all probiotics help diarrhea. And only certain types of the condition seem to get better when you take them. So which ones may help and when?

Diarrhea in Children

Some of the best evidence on the benefits of probiotics comes from studies of diarrhea in children, especially cases caused by rotavirus.

Probiotics can cut bouts of infectious diarrhea by half a day to about 2 days.

The bacteria strains most likely to help are Lactobacilllus rhamnosus GG, Lactobacillus reuteri, and Saccharomyces boulardii. A mix of a few different probiotics may also help treat this type of diarrhea.

Antibiotic-Associated Diarrhea

Antibiotics kill the bad germs in your body that make you sick, but they also kill the good bacteria. This can disrupt the normal balance in your intestines, leading to diarrhea. It’s common for 10% to 30% of people taking these medicines.

Studies of both children and adults have shown that probiotics taken before and with antibiotics can lower the risk of diarrhea. Saccharomyces boulardii and Lactobacillus GG seem to be the most effective.

Travelers’ Diarrhea

Travelers often battle diarrhea caused by contaminated food or water. Up to 10% of people who get the condition while traveling end up with a case that lasts longer than 4 weeks.

Evidence is mixed on whether probiotics work for this condition. A 2007 report found that probiotics lowered the risk of getting travelers’ diarrhea. But other studies have shown that they don’t really help. The strongest evidence pointed to benefits from S. boulardii, Lactobacillus acidophilus, and Bifidobacteria bifidum.

Diarrhea Caused By C. Difficile

Infection with C. difficile bacteria causes severe and sometimes life-threatening diarrhea and inflammation in the colon, called colitis. Probiotics may keep you from getting this germ. And there’s some evidence that probiotics may keep C. difficile from coming back. That’s important, since repeat infections become hard to control.

Scientists have studied Saccharomyces boulardii and Lactobacillus GG the most against this type of bacteria. In one large study, patients with recurrent diarrhea took either a probiotic or a placebo. Only 9 out of 26 people in the probiotics group had more diarrhea. In the placebo group, 22 out of 34 had diarrhea that came back.

Inflammatory Bowel Disease

Probiotics may help treat ulcerative colitis, a form of inflammatory bowel disease (IBD). There are some studies that show probiotics may also help Crohn's disease, the other form of IBD, but the evidence is not strong.

Where to Find Probiotics

Most health food stores now stock dozens of brands of probiotic foods and supplements, like yogurts or dairy drinks, capsules, powders, and liquids.

Look for probiotics that have a specific type of bacteria that has been tested and found effective . One key is to look for products that say that they’re viable “through end of shelf life” rather than “at time of manufacture.”

Top Foods With Probiotics

Are all yogurts good? Are aged cheeses better? Find out here.
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