How to Pick the Best Probiotic for You, and 8 Quality Brands to Buy

Probiotics — aka friendly bacteria and yeast — reside in your body, delivering all sorts of health benefits. Add probiotic-rich foods like yogurt and kimchi to your diet and you'll naturally take in these microorganisms.

But if those foods aren't appealing, you can also turn to supplements.

"Many of my patients have found benefit with probiotics," Bryan Curtin, MD, MHSc, director of the Center for Neurogastroenterology and GI Motility at Mercy Medical Center, tells LIVESTRONG.com.

"Probiotics cause benefit by multiple mechanisms," Dr. Curtin explains, adding that this includes suppressing the growth of bad bacteria, improving the gut's natural defenses and supporting the immune system.

But much more remains to be known when it comes to the positive effects of probiotics. "The major GI societies in the U.S. have made position statements that it is unclear what strains, dosing and regimens are beneficial for the general use of probiotics," Dr. Curtin says.

If you browse online or peruse the vitamins and supplements aisle in a drug store, you'll find many, many options. Here's what to keep in mind as you choose a probiotic supplement.

CFU stands for colony-forming units and it's "an estimate of the number of viable cells capable of forming new bacterial colonies in the gut," says Carielle Nikkel, RDN, vice president of nutrition at Persona Nutrition.

"Doses of 5 to 20 billion CFU per day are shown to be effective in supporting digestive and immune health," she says.

Some products will tout that they have "megadoses" of probiotics, Nikkel points out — but higher CFUs don't always equate to better or more health benefits, per the National Institutes of Health (NIH).

Choose a reputable brand before making a purchase. "Look for a brand that has doctors, dietitians and other nutrition experts working behind the scenes," Nikkel recommends.

You can also look for third-party certification on the container from organizations including:

• United States Pharmacopeia
• ConsumerLab
• NSF International

"When you read the label, look for additives or allergens in the probiotic capsules that may not work for your body — especially if you have food sensitivities or dietary restrictions," says gut health dietitian Laura Poe Mathes, RD.

If the information isn't available there, you can check on the company's website or reach out for more information, she says.

Along with an alphanumeric, bacteria are identified by their genus, species and strain, per the World Gastroenterology Organisation Global Guidelines.

Within each genus, there are many species and strains, per the California Dairy Research Foundation. These are presented in order from the broadest category to the most specific. So, for ​Lactobacillus rhamnosus​ GG, the genus is ​Lactobacillus​, the species is ​rhamnosus​ and the strain is ​GG​, per the California Dairy Research Foundation.

Here are some of the most common genera found in probiotic supplements, per the NIH:

• ​Lactobacillus​: This may help with diarrhea, as well as allergies, stomach pain and constipation, per the U.S. National Library of Medicine (NLM).
• ​Bifidobacterium​: This good bacteria may help with constipation and airway infections, per NLM.
• ​Saccharomyces​: This yeast may be effective against diarrhea and stomach pain, per a December 2020 report from ConsumerLab.
• ​Streptococcus​: This is effective with some forms of diarrhea, per ConsumerLab.
• ​Bacillus​: This helps with abdominal pain, bloating and constipation, per ConsumerLab.

"The most important thing to look for is the right species of bacteria (or yeast) tailored to your specific health needs," Poe Mathes says.

If you're looking to improve your overall digestive health, a supplement with many strains may be appealing.

"I typically recommend supplements with multiple species in it, helping to promote the most diversity in the microbiome possible; but for some, single-strain supplements may be more appropriate," Poe Mathes says.

The instructions call for you to take one of these large capsules daily. This supplement is vegetarian and does not need to be refrigerated. It contains many strains of probiotics, including ​Lactobacillus gasseri​, ​Bifidobacterium bifidum​, ​Lactobacillus plantarum​ and more.

Some research suggests probiotics may help ward off vaginal infections, per a December 2020 report from ConsumerLab, which provides independent test results for health and nutrition products.

This is one area where more studies are needed to sort out what's possible. ​Lactobacillus rhamnosus​ GR-1 appears to be the best probiotic for vaginal health, according to Harvard Health Publishing.

This is a ConsumerLab top pick for preventing vaginal infections. The combination of strains present in this supplement (which includes ​Lactobacillus rhamnosus​ GR-1) might reduce potentially bad bacteria in the vagina, per the ConsumerLab report.

"Probiotics are particularly helpful with diarrhea, especially after recent antibiotic usage," Dr. Curtin says. ​Lactobacillus rhamnosus​ GG and ​Saccharomyces boulardii​ both help cut down on antibiotics-associated diarrhea, which affects 30 percent of people who take antibiotics, per the NIH.

Not only does this soy-free prebiotic fiber supp ease diarrhea that comes with taking antibiotics, but it can also help with traveler's diarrhea, per ConsumerLab. Begin taking when you start your antibiotics course and continue for a full week after you've completed the script, according to the ConsumerLab report.

Struggling to go can be uncomfortable. "Probiotics can be safely tried for mild constipation, in addition to adequate hydration, fiber intake and magnesium supplementation," Dr. Curtin says.

Compared to a placebo, ​Lactobacillus reuteri​ helps improve the frequency of bowel movements, per a small December 2014 study in the ​Journal of Gastrointestinal and Liver Diseases​. (The same effect was seen in previous studies in children.)

As well as being effective for colic in infants, taking these drops — which contain ​Lactobacillus reuteri​, a good bacteria — twice a day might help with constipation in adults, per ConsumerLab.

Probiotics may ease IBS symptoms, according to the Canadian Society of Intestinal Research, which notes that more research will help understand the link a bit better.

Strains of ​Lactobacillus​ bacteria — including ​Lactobacillus plantarum​, ​Lactobacillus bulgaricus​ and ​Lactobacillus acidophilus​ — may help with IBS symptoms, per the Canadian Society of Intestinal Research.

Taking this large capsule with 112.5 billion CFUs may help with bloating for some forms of IBS, per ConsumerLab. It's their top pick for both reducing bloating in diarrhea-predominant IBS and for pouchitis (inflammation that can occur after surgery for ulcerative colitis, per the Mayo Clinic). Note that this product contains milk.

People with overweight or obesity have lower bacterial diversity in their gut, per a June 2018 analysis in ​The BMJ​.

And certain probiotics may be beneficial when it comes to weight loss — ​Lactobacillus gasseri​ SBT 2055 and ​Lactobacillus rhamnosus​ ATCC 53103 as well as a combination of ​L. rhamnosus​ ATCC 53102 and ​Bifidobacterium lactis​ Bb12 are linked to reduced body weight and weight gain, per a March 2014 review in ​Beneficial Microbes​.

However, clinical trials have shown inconsistent results, per the NIH. In addition to particular strains, your weight and sex may play a role in how effective probiotics are.

A single daily capsule, which is medium- to large-sized, contains ​Lactobacillus gasseri​ as well as several other strains.

The gut plays a major role in your mood — so much so that it's referred to as your "second brain." The gut and your brain communicate with each other — that means psychological interventions may help with gut-related problems, per Johns Hopkins Medicine.

And the reverse may be true as well: One small study found that taking probiotics is linked to easing negative thoughts due to a sad mood, per August 2015 research in ​Brain, Behavior, and Immunity​. And probiotics are linked to helping with symptoms of psychological conditions (such as depression and anxiety), per an October 2016 review in the ​Journal of Neurogastroenterology and Motility​ that looked at both animal and human studies.

Taking ​Lactobacillus acidophilus​, ​Lactobacillus casei​ and ​Bifidobacterium bifidum​ were observed to ease depression symptoms in people with major depressive disorder in a small March 2016 study in ​Nutrition​​.​ More research is needed to understand this gut-brain relationship.

This one daily capsule contains several probiotic strains (including the three called out in the ​Nutrition​ study).

A surprising amount — an estimated 70 percent — of immune cells are found in your gut, per a September 2008 article in ​Clinical and Experimental Immunology​. What happens in your gut affects many parts of your body, including the immune system.

While more research is needed in this area, there's evidence that probiotics with the ​Lactobacillus​ and ​Bifidobacterium​ strains are linked to reduced symptoms of colds and upper respiratory infections, per the ConsumerLab review.

For example, in one study, people prone to getting colds in the winter were divided up into two groups — one group drank a probiotic drink with ​Lactobacillus paracasei​, ​Lactobacillus casei​ and ​Lactobacillus fermentium​ while the other group had a placebo drink without any probiotics. The probiotic drink was observed to reduce the incidence of upper respiratory infections and flu-like symptoms, per the June 2018 study in ​Synthetic and Systems Biotechnology​.

Taking probiotics may also help with inflammation: Compared to a group taking a placebo, older adults taking a probiotic supplement had more anti-inflammatory markers, per an April 2015 study in the ​Journal of the American College of Nutrition​.

You'll take one large capsule a day with food. This supplement is vegetarian and both glucose- and lactose-free. It contains ​Lactobacillus acidophilus​ (CUL 60 and CUL 21), ​Bifidobacterium bifidum​ (CUL 20) and ​Bifidobacterium animalis​ (CUL 34).