Choosing the Right Probiotic: A Science-Based Guide

Top probiotic supplements for gut health

When choosing a probiotic health supplement, price or brand name should not be your deciding factor. It’s whether or not the strains in the supplement have been studied in humans and have been shown to impact gut health.

• Lactobacillus rhamnosus GG is a probiotic supported by hundreds of human studies and has been shown to support digestive comfort and immune health.¹
• Lactobacillus acidophilus NCFM: NCFM is one of the most well-studied strains of L. acidophilus and is shown to support digestive comfort by helping the body break down food.²
• Bifidobacterium lactis HN019 is shown to help the growth of healthy bacteria in the gut and support bowel regularity, comfort, and less bloating.³
• Lactobacillus plantarum LP-115: This research-backed strain is shown to support immune health in the gut.⁴
• Lactobacillus casei LC-11 is shown to help balance the gut microbiome.⁵

AG1 Next Gen includes all five of these strains, alongside prebiotics and plant-based digestive enzymes, as part of a formula designed for daily foundational support.* In three clinical studies, AG1 Next Gen was shown to enrich key probiotic species in the gut.^{6 7 8}

How to choose the right probiotic supplement

There’s no one-size-fits-all answer to which probiotic supplement is best for you. Everyone’s gut microbiome is unique. However, there are several trustworthy factors you can look for to weed out poorly formulated products.

Strain specificity over quantity

CFU counts (colony-forming unit counts) show up on most probiotic labels. But a larger CFU count doesn’t necessarily equal a better product.

Instead, look to see if the strains included have been clinically studied in humans—and if they’re provided at levels supported by research. You’ll most likely get less for your money with doses of poorly studied strains than from probiotics with researched strains at doses shown to be effective.

How a brand counts its probiotics matters too. AG1 Next Gen uses digital PCR (dPCR) testing—a more accurate method than the traditional CFU plate count—to measure the total viable probiotic cells at the strain level. Unlike other methods, dPCR delivers results with elevated precision and accuracy, counting live cells that might be missed, especially if laboratory conditions are unoptimized. It’s a higher standard of quality verification that sets AG1 Next Gen apart from the others.

Survivability

Probiotics must survive gastric acid and bile to reach the colon, where they can exert the greatest effect. Look for products that show that their probiotics have an impact on the gut microbiome through clinical research. Measurable changes in the microbiome indicate that strains are surviving digestion and reaching the colon, where they can do their job. In three clinical trials, AG1 Next Gen was shown to enrich key probiotic species in the gut.*^6,7,8

The prebiotic environment

A probiotic without a prebiotic is like throwing seeds on rocky soil. Prebiotics are fermentable fibers and other compounds that feed friendly bacteria, and they can help probiotics get rooted in the gut and stay active there. Some, like inulin, have been found to promote the growth of beneficial bacterial species as well as the production of short-chain fatty acids that support gut barrier function.*¹¹ Look for prebiotics in the ingredient list when shopping for probiotics for gut health.

Format and consistency

Capsules, powders, and drinks can all work, but what’s important is whether you’ll take the probiotic daily. Third-party clinical research suggests significant changes in the gut microbiome occur slowly, over weeks and months of regular use, and are also reliant on diet, lifestyle, and starting gut health.¹² If you take a probiotic regularly, it will always beat one you take occasionally.

FAQs about probiotics

There are some misconceptions around probiotics, so let’s get into the facts.

What are the signs you would benefit from a probiotic?

Digestive challenges like occasional discomfort, bloating, or irregularity are some of the top reasons people seek out a probiotic. However, probiotics should be thought of as regular dietary supplements that help cultivate a healthy gut microbiome—not a reactive measure to a health concern. As with any supplement, consult your healthcare provider with any questions about your individual health needs.

Is it good to take a probiotic every day?

Yes, consistency is key when it comes to probiotics. The microbiome is constantly changing in response to what you put into your body each day. That’s why daily use promotes the gradual changes over time that research shows can lead to meaningful gut health outcomes.

Which probiotics are best for digestive health?

Supplement with strains that have the strongest clinical research behind them for digestive comfort and microbiome support, such as Lactobacillus rhamnosus GG, Lactobacillus acidophilus NCFM, and Bifidobacterium lactis HN019.

Do probiotics help with digestive issues?

Some research indicates that certain strains may support digestive comfort and regularity during times of dietary shifts or stress.⁹ AG1 Next Gen is designed to support normal digestive function as part of a daily nutrition routine, not to address diagnosed GI conditions. If you experience persistent issues, contact your healthcare provider.

Can you take probiotics with GLP-1?

If you are taking a GLP-1 receptor agonist, always consult your healthcare provider before introducing a new supplement into your regimen, probiotics included.

Making the right choice for your gut

The key to finding the best probiotic supplement for your gut isn’t reading the claims on a label or looking for the highest dose. The key is finding a formula centered around strains with clinical research behind them that can complement a fiber-filled diet of whole foods—not replace it.

AG1 Next Gen is clinically shown to fill common nutrient gaps and support gut health, combining five clinically studied probiotic strains with prebiotics and plant-based digestive enzymes in a single daily scoop.* AG1 is NSF Certified for Sport® and third-party tested—one daily habit designed to support the foundation your gut health is built on.*

References:

1. Kankainen M, Paulin L, Tynkkynen S, et al. Comparative genomic analysis of Lactobacillus rhamnosus GG reveals pili containing a human-mucus binding protein. Proc Natl Acad Sci USA. 2009;106(40):17193-17198.
2. Leyer GJ, Li S, Mubasher ME, Reifer C, Ouwehand AC. Probiotic effects on… incidence and duration in children. Pediatrics. 2009;124(2):e172-e179.
3. Agrawal A, Houghton LA, Morris J, et al. Clinical trial: the effects of a fermented milk product containing Bifidobacterium lactis DN-173 010 on abdominal distension and gastrointestinal transit in…. Aliment Pharmacol Ther. 2009;29(1):104-114.
4. Martínez I, Lattimer JM, Hubach KL, et al. Gut microbiome composition is linked to whole grain-induced immunological improvements. ISME J. 2013;7(2):269-280.
5. Shida K, Nanno M. Probiotics and immunology: separating the wheat from the chaff. Trends Immunol. 2008;29(11):565-573.
6. In a triple-blind, randomized, placebo-controlled parallel-designed clinical trial evaluating nutrient biomarkers and microbiome shifts in 105 healthy adults ages 20–59 over the course of 12 weeks.
7. In a double-blind, randomized, placebo-controlled 2-week cross-over clinical trial assessing nutrient gaps and microbiome shifts in 20 active adults ages 19–37.
8. In a double-blind, randomized, placebo-controlled 2-week cross-over clinical trial assessing nutrient gaps and microbiome assessments of 24 healthy adults with occasional GI distress ages 26–59.
9. Hungin APS, Mitchell CR, Whorwell P, et al. Systematic review: probiotics in the management of lower gastrointestinal signs—an updated evidence-based international consensus. Aliment Pharmacol Ther. 2018;47(8):1054-1070.
10. Rowland I, Gibson G, Heinken A, et al. Gut microbiota functions: metabolism of nutrients and other food components. Eur J Nutr. 2018;57(1):1-24.
11. Edo GI, Mafe AN, Ali ABM, et al. Mechanistic insights into β-glucans and gut microbiota interactions for enhancing human health. Discov Food. 2025;5:282.
12. Maftei NM, Raileanu CR, Balta AA, et al. The potential impact of probiotics on human health: an update on their health-promoting properties. Microorganisms. 2024;12(2):234.