• Taking probiotics while on antibiotics does not significantly boost beneficial gut bacteria, according to new research.
• The findings debunks the previous notion that it's important to take probiotics along with antibiotics, when prescribed, to maintain the gut's microbiome.
• Experts maintain that it's better to get probiotics from fermented whole foods—like yogurt, kimchi, and sourdough bread—rather than from supplements.

Supplementing antibiotics with probiotics doesn’t restore beneficial bacteria in the gut, a new study has found. 

Antibiotics fight harmful bacteria that cause illness, but that’s not the only thing the prescription drugs go after. They also kill the “good” bacteria necessary for essential bodily functions, such as digestion and keeping harmful bacteria in check.

Because probiotics add beneficial bacteria to the gut, taking probiotic supplements while on antibiotics has become a popular strategy for offsetting bacteria loss and keeping the gut microbiome balanced. 

The new research, however, debunks that previous notion, showing that the tactic may be ineffective.

To reach this conclusion, researchers analyzed 15 randomized controlled trials examining the differences in gut microbiome diversity between participants taking antibiotics with probiotics and without them. Nearly 1,200 people were included in the studies.

In five studies selected for meta-analysis, the researchers found that people who took probiotics along with antibiotics boosted gut microbiome diversity by a minuscule amount—just 0.23%. The researchers concluded that taking probiotic supplements with antibiotics “was not found to be influential on microbiome diversity.” 

“This is the first meta-analysis and the most comprehensive review of the topic to date using high-quality methods,” the researchers wrote in the study, published in July in the journal BMC Medicine.

Why Probiotic Supplements Don't Always Have a Big Impact

There are several reasons why probiotic supplements don’t significantly change gut microbiome composition, Arik Alper, MD, a pediatric gastroenterologist at Yale New Haven Hospital and assistant professor of pediatrics (GI) at Yale School of Medicine, told Health.

For one, there aren’t enough microbes reaching the gut to make a big dent, he said. Supplement dosages aren’t typically high enough to begin with, and gastric acid can kill many bacterial strains.

The antibiotics themselves may also kill the probiotics you're supplementing with, Alper added, which is why you may actually want to stop using a probiotic supplement you had previously been using before starting an antibiotic.

Probiotic supplements also typically contain gut microbes that settle in the small intestine, but the vast majority of gut microbiota colonizes in the colon, Alper explained.

How Probiotic Supplements Can Help

But that’s not to say that it’s never helpful to take probiotics in conjunction with antibiotics, Alper acknowledged.

“The most common and useful clinical indication for probiotics is prevention of antibiotic-associated diarrhea,” he said. “In general, probiotics are better for diarrheal illnesses and not constipation.”

Even then, though, probiotic supplements would only help in certain circumstances, Alper said. 

“There are only two probiotics that would be beneficial for this specific indication: a yeast named Sacharomyces boulardii and to a lesser extent, the bacteria Lactobacillus rhamnosus,” he explained. “Even those two gut microbes would be effective only for specific antibiotics.”

Choosing Food Over Supplements

It’s generally better to get probiotics from whole foods than supplements, Madhav Desai, MD, a gastroenterologist with UTHealth Houston, told Health. “Reliance should be on a wholesome, unadulterated natural prebiotic diet containing a combination of fruits and vegetables,” he said. 

Fermented foods such as yogurt, pickles, kimchi, and sourdough bread are also high in probiotics.

If you do opt for prebiotic supplements, Desai recommended reviewing the label and paying attention to the microbiome colonies the supplement contains. That way, you can research how they might interact with a specific antibiotic. 

Alper advised speaking to a healthcare provider about which probiotics to use regardless of the reason you plan on taking them.

“You should follow specific guidelines from your doctor regarding which probiotics to use, and for how long, and what dosage,” he said. “Probiotics have side effects, and therefore you should be careful when using probiotics, especially if not indicated by your doctor.”