Note: The U.S. Food and Drug Administration (FDA) does not approve supplements for safety or effectiveness. Talk to a healthcare professional about whether a supplement is the right fit for your individual health, and about any potential drug interactions or safety concerns.
“I generally think of probiotics as an adjunct to other treatments. While many people report benefits, the consensus on the scientific evidence is still limited, and expectations should be realistic,” says Daniel Kao, MD, PhD, an associate professor of medicine in the division of gastroenterology and hepatology at the University of Colorado Anschutz in Aurora.
If you are considering taking a probiotic in supplement form, it’s important to know that supplements are not regulated by the U.S. Food and Drug Administration, and there is no consensus on effective dosing for probiotics.
And not all strains of probiotics confer the same effects, says Hector Gonzalez, MD, a board-certified gastroenterologist with Gastro Health in Plantation, Florida.
1. Lactobacillus Acidophilus May Prevent Diarrhea From Antibiotics
A study published in 2024 found that eating yogurt was as effective as taking probiotic capsules for preventing diarrhea from antibiotics in children.
If you’re affected by antibiotic-associated diarrhea, talk to your doctor about whether a supplement or food is a better idea. Dr. Kao also recommends checking the Alliance for Education on Probiotics’ online guide to food and supplement sources of L. acidophilus and other strains. “It is easy to use and summarizes a huge amount of information about how specific probiotics have been studied, rates the level of confidence in using many probiotics for specific health concerns, and even provides references to relevant studies,” he says.
For general digestive benefits like more regular bowel movements, the scientific support for L. acidophilus isn’t as strong. Gonzalez says that evidence for using L. acidophilus for conditions like irritable bowel syndrome (IBS) and general gastrointestinal health is “limited and not well supported by clinical trial data or guideline recommendations.”
You should be wary of other health benefits associated with this strain, too. “Other claims include improved cholesterol, vaginal health, and general gut support, but data is limited, mixed, and highly strain or formulation dependent,” says Yi Min Teo, RD, a digestive health dietitian in Irvine, California.
2. Lacticaseibacillus Rhamnosus GR-1 May Reduce Bacterial Vaginosis and UTIs
Among the many probiotics sold under the banner of women’s health, Lacticaseibacillus rhamnosus GR-1 is one of the most thoroughly researched — and the results seem promising.
“L. rhamnosus GR-1 is well studied for reducing the recurrence of bacterial vaginosis and urinary tract infections [UTIs] in women,” says Gonzalez. One review showed that L. rhamnosus GR-1 can help prevent both of these conditions. Other research has suggested that the strain may do this by suppressing the secretion of pro-inflammatory cells in the female urogenital tract.
Foods like yogurt and cheese may be supplemented with this strain. It’s difficult to tell how much of it a food contains, compared with a supplement, however. If you’d like to use L. rhamnosus GR-1 to help prevent a specific condition like bacterial vaginosis or a UTI, your healthcare provider may recommend a supplement with a known quantity.
3. Streptococcus Thermophilus May Improve Lactose Intolerance Symptoms
Supplementing with this probiotic is not a cure for lactose intolerance. To keep up the digestion benefits, you need to keep supplementing with this probiotic strain indefinitely. “A common misconception is that probiotics repopulate the gut with good bacteria,” says Kao. “In reality, probiotics are transient: They pass through the digestive tract and are cleared within days (sometimes weeks) of stopping them.”
Another study showed digestive benefits from a dosage of 1 billion colony-forming units, especially when combined with another strain called Lactobacillus delbrückii — but ask your doctor about the dose that’s right for you and whether it’s better to get it from food or a supplement; your doctor may also suggest alternative treatments, such as Lactaid.
4. Limosilactobacillus Reuteri May Reduce Infant Colic
Parents of colicky babies know how difficult endless nights of fussing can be. The probiotic strain Limosilactobacillus reuteri may help bring infants some much needed calm.
“Multiple randomized, controlled trials and meta-analyses show that there’s reduced crying and fussing versus a placebo,” says Teo. “Benefits are clearest in exclusively breastfed infants. Data are less consistent in formula-fed infants.” Supplements are typically given in the form of liquid drops.
One meta-analysis found that breastfed infants given L. reuteri cried less often and had fewer gastrointestinal symptoms without any adverse effects. Ask your pediatrician if this strain is appropriate for your child.
5. Bifidobacterium Longum May Improve Mood and Alleviate IBS
According to Kao, there may be several good reasons to try Bifidobacterium longum as a supplement, including an elevated mood and improvements with IBS symptoms.
As far as IBS goes, multiple studies have linked this strain with outcomes like better quality of life and lower disease severity in people with the condition.
The Takeaway
- Probiotics, which are live microorganisms found in foods and supplements, have grown into a booming wellness trend, with some research showing that they may support digestion, vaginal and urinary tract health, and mood; however, supporting evidence is not robust enough that doctors strongly recommend them.
- Not all probiotic strains have the same effects; evidence-based benefits vary widely, from L. acidophilus for diarrhea relief to B. longum for mood and IBS symptom support.
- Experts emphasize choosing probiotic strains matched to specific health goals, since results can depend on the individual strain, formulation, and consistent use.
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