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Here's What You Need to Know About Probiotics: Uses, Safety and More

A registered dietitian, CEO of a supplement testing lab and a NASM-certified nutrition coach discuss using probiotics to boost your gut health.
A man in a blue shirt holding a bottle of probiotic supplements as he stands in front of a shelf full of similar products

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In the last 20 years, researchers have continued to discover more ways to use probiotics for better health. In response, probiotic supplements have grown in popularity, resulting in more brands offering them. These supplements come in many forms, like capsules, gummies and liquid probiotic drinks, or as part of the formula for multivitamins or greens powders.

As a longtime user of probiotics, I’m pretty familiar with what to expect from a probiotic supplement. Anecdotally, I’ve narrowed down which strains of bacteria in a probiotic seem to help me the most and which cause side effects. But for this article, I wanted to take a deeper dive into the science behind probiotics so that I could answer questions like what they are, if you should take them every day and which specific strands are the best.

To help answer my questions, I interviewed Sean Callan, Ph.D. and CEO of Ellipse Analytics (a third-party supplement testing lab) and Danielle Smith, Registered Dietitian at Top Nutrition Coaching.

The products featured in this article have been independently reviewed. When you buy something through the retail links on this page, we may earn commission at no cost to you, the reader. The Sports Illustrated editorial team is not involved in the creation of this content. Learn more here.

What Are Probiotics?

Probiotics are “live microorganisms that help maintain a healthy balance of gut bacteria,” explains Smith. Probiotics are good bacteria you want to grow and thrive inside your body. You're not alone if the idea of “good” bacteria is new to you. Callan adds that most people don’t realize that the human body has “many living organisms—microscopic living things that play a huge role in how we function in our daily lives.”

What Do Probiotics Do?

Probiotics are bacteria, but what exactly do they do? When you take a probiotic, the goal is to add specific, beneficial bacteria strains to your gut to encourage or restore balance to your gut microbiome—the collection of living organisms in your gut.

Callan says that your gut microbiome can include multiple types of bacteria or microscopic fungi, and ideally, these organisms “live in harmony inside our intestines.” However, the harmony can be disrupted by disease, antibiotic treatment, poor diet or other causes. Restoring that balance is important because growing research indicates that gut health should be considered one of the key indicators of a healthy body.

Bottom line: Probiotics are concentrated bacteria that can colonize your digestive tract, which may help lead to a healthier gut microbiome. Probiotics deliver the “good” bacteria to your digestive tract.

Benefits of Probiotics

Smith notes that a thriving population of good bacteria in your gut can “aid in breaking down food and absorbing nutrients…support the immune system, as a significant portion of the immune system is housed in the gut…[and] strengthen the gut barrier, reducing the risk of harmful substances passing into the bloodstream."

My own research confirms this, but the study of probiotics on human health is still relatively new. From that perspective, it seems like the benefits of probiotics can be separated into two categories: established benefits and potential benefits. According to the NIH, the established benefits of probiotics include:

  • Helping your body digest food
  • Killing disease-causing cells that try to colonize your digestive tract
  • Producing vitamins and minerals

According to a review of the available research, the potential benefits of probiotics include:

Related Post: Top Benefits of Probiotics for Women

When to Take Probiotics

As a probiotics user myself, one of my biggest questions has been when I should take probiotics. Sometimes, I take them in the morning before I eat, and sometimes I take them with meals. However, none of the products I’ve used have given me specific guidelines on the most beneficial timing.

According to a study of how meal timing affects the efficiency of probiotic supplements, the best time to take probiotics is with or just before a meal high in fats. The study noted that some probiotic supplements are coated with (or contained in capsules made from) technologies designed to deliver the bacteria to the gut, but those products seem to be just as efficient when taken with or without food.

Related Post: Best Probiotics for Constipation

Most Common Types Of Probiotics

Six nondescript capsules against a neutral background representing the size and shape of common probiotic supplements

There are seven major probiotic genera (families that have multiple strains) that are commonly used in probiotic supplements, but four have the most researched benefits: lactobacillus, bifidobacterium, saccharomyces and streptococcus.


Lactobacillus is a lactic acid bacteria that colonizes your GI tract. The most research-supported benefits of lactobacillus include fighting inflammation and providing a barrier of defense between harmful bacteria and viruses in your digestive tract and the wall of your intestines (where your body absorbs nutrients).


Bifidobacterium is one of the first bacteria to colonize your GI tract as a baby. This bacteria is thought to be responsible for developing a properly functioning immune system, and research shows that bifidobacterium may help keep harmful bacteria from finding a place in your GI tract and may prevent a variety of infections.


Saccharomyces is classified as a fungi, and although it hasn't been studied as much as some other probiotics, small clinical trials have produced positive results that indicate it may be useful in alleviating symptoms of some GI diseases like irritable bowel syndrome (IBS) and infections from intestinal parasites. Other studies have used saccharomyces to help people with Crohn’s Disease and Ulcerative Colitis stay in remission, but the results have been mixed.

One study even found that using probiotic yeasts from saccharomyces strains may be useful as an alternative treatment for diseases rapidly growing resistant to traditional antibiotic treatments. More definitive studies are needed to confirm this, but the evidence is encouraging.


Streptococcus is another probiotic genera, and the streptococcus thermophilus strain is the most common bacteria strain used in the dairy industry. You likely consume it regularly if you eat yogurt, cheese, cow’s milk or other dairy products. According to a clinical trial, streptococcus thermophilus supplements produced beneficial changes in the immune system compared to a placebo. More studies need to be done to confirm the long-term benefits of this bacteria, but the results are promising.

Are Probiotics Safe

For general use

Both Smith and Callan reiterate that probiotics are generally considered safe for use. If you are a “healthy” adult—meaning you don’t have any known health conditions that require active treatment—probiotics should be safe for you to use.

Callan says, “The U.S. Food and Drug Administration (FDA) has given select probiotics its Generally Recognized as Safe (“GRAS”) designation 3, meaning the FDA has reviewed the available evidence and has approved probiotics for use in food and supplement products.”

When to see your doctor

It's best to consult your doctor or a licensed medical professional before using any supplements, including probiotics. However, if you’ve already started using probiotics and are experiencing negative side effects like abdominal pain, abnormal fatigue, dizziness or any other symptom, stop using the supplement immediately and consult your doctor.

There are also certain diseases like Crohn’s Disease, Ulcerative Colitis and other chronic illnesses that may cause an adverse reaction to probiotics. If you have one of these diseases or wonder if you are at risk for adverse effects, talk with your doctor.

Sources of Probiotics

Probiotic foods

You can also get probiotics from fermented foods like miso, kimchi, sauerkraut, kefir, yogurt, kombucha, sourdough bread and others. Traditional medicine practitioners have used fermented foods like these to treat bloating, persistent nausea after meals and other digestive system problems for centuries.

Speaking from experience, probiotic foods can be less intimidating than supplements if you’re concerned about your gut health. I highly recommend you talk to your health care provider, primary care doctor or registered dietitian about your concerns. They’ll be able to work with you to find what source of probiotics may be most beneficial for you.

Probiotic supplements

Probiotic supplements are growing in popularity. You can find probiotics in standalone supplements or included in multivitamins, greens powders and as part of prebiotic blends. Probiotics are generally considered safe, but many studies have found that probiotic supplements are not all created equal. Probiotics have to survive the stomach to get any benefits from taking them.

Many standard probiotic supplements use a simple vegetable capsule, which starts dissolving in your mouth before you swallow it. These supplements are not likely to offer any benefit, and anecdotally, I can confirm that I’ve stopped using several supplements because I did not think they were working.

To sum it up: Probiotic supplements are considered generally safe for both men and women, but make sure you know what you’re getting from your supplement. Some of the best probiotics use innovative technology in the capsule to help the bacteria survive the enzymes and stomach acid before releasing it into the lower digestive tract.

Related Post: The Best Probiotics Supplements for Men, According to RDs

Our Favorite Probiotics Products

Ritual Synbiotic+

A light blue bottle of Ritual Synbiotic+ probiotic supplement with blurred weight plates in the background

Ritual Synbiotic+ is one of my favorite probiotic supplements because it has both probiotics and prebiotics in one supplement (which is what makes it a synbiotic). Prebiotics are fibers that act as a sort of food for probiotic bacteria to feed on, and may help the probiotic bacteria colonize your gut faster and establish a stronger presence.

Ritual also uses a delayed-release capsule, which the brand says is designed to help the probiotics survive your digestive process until they’re released in the lower digestive tract.

Check out our Ritual Synbiotic+ review for more insight on this probiotic supplement.

Related Post: Prebiotics vs. Probiotics: Which One Is Right For You?

YourBiology gut+

A bottle of gut+ by yourbiology probiotic supplement standing on a light brown wooden table with a black backdrop

I like YourBiology gut+ because it has four different strains of probiotics: Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus paracasei and Lactobacillus plantarum. These four well-studied probiotic strains may help rebalance your gut bacteria after antibiotics.

Our tester, Lindsay Scheele, CPT, noted that gut+ has a loading phase that requires you to take one capsule per day for the first four days, two capsules for days five through nine and three capsules per day after day nine. Scheele said the capsules were "about the length of a nickel and very easy to swallow with no aftertaste."

Transparent Labs Gut Health Probiotic

Transparent Labs Gut Health Probiotic white bottle with blue and black writing with blurred weight plates in the background

Transparent Labs Gut Health probiotic supplement combines multiple Bifidobacterium and Lactobacillus strains with Streptococcus to deliver 100 billion CFUs of probiotics per serving. That’s about 10 times the effective dose of 10 billion CFUs, but that means this product contains high amounts of each strain, which may increase the chances of the good bacteria colonizing your gut.

Transparent Labs products are also third-party tested for purity and potency, so you know that you get exactly what is stated on the label.

Final Thoughts

If you’re looking for a supplement to support your gut health in response to GI problems like IBS, antibiotic-related diarrhea, poor digestion or something else, then probiotics may be a great place to start. Several forms of probiotic supplements are readily available, and they are generally considered safe. You can also incorporate more probiotic foods into your diet. Make sure to talk with your doctor to find out if you should be supplementing with a probiotic.

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