There’s hard science saying probiotics can help with certain kinds of diarrhea, but for other conditions, it’s a bit of a crapshoot (har har). Lebwohl says that one of the first things that needs to change for probiotics to go widespread legit in the medical community is their regulation. Since they’re currently marketed as dietary supplements, they’re not subjected to the same FDA standards that medications are. That means that not only have they not been proven to work, it also means there’s also no assurance that what’s on the labels of these products actually matches what’s inside the bottle.

There are four significant takeaways from this study: (1) murine gut mucosal probiotic colonization is only mildly enhanced by antibiotics, (2) Human gut mucosal probiotic colonization is significantly enhanced by antibiotics, (3) After taking antibiotics, probiotics delay gut microbiome and transcriptome reconstitution in mice and humans, (4) Autologous fecal microbiome transplant (aFMT) restores mucosal microbiome and gut transcriptome reconstitution. 
According to the NIH, probiotic supplements contain many microorganisms that are the same as or similar to the ones that naturally live in your body, but there's still a lot of research to be done on probiotics and how they work. It's important to keep in mind that not all probiotics have the same effects and that taking probiotics isn't a guarantee of better health. And while they're generally safe for healthy people to take, with side effects being limited to mild digestive discomfort, they could interact with certain medications or pose health risks to people with underlying medical problems — that's why it's smart to talk to your doctor before getting started with a supplement.

Billions Of CFU – One of the first things you will notice on a bottle of probiotics is the phrase “X Billion CFU.” Probiotics vary in the number of billions of cultures they pack in each capsule, but the lingo always stays the same. CFU stands for Colony Forming Units, so if the bottle reads 5 Billion CFU, it means that there are 5 Billion Colony Forming Units per capsule. The higher the number, the more flora contained in each pill.
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Coming in at a close second, our runner-up as the best probiotic for women is the Culturelle Women’s Healthy Balance Probiotic. As the #1 recommended brand by pharmacists, it is easy to see why so many women are turning to Culturelle for their digestive health. Featuring the LGG culture and a laundry list of other healthy bacteria, this probiotic offers a wonderful balance between digestive and feminine health. The Culturelle Women’s Healthy Balance Probiotic is also taken in an easy, chewable tablet and can even be taken during pregnancy, making it one of the most versatile formulas we reviewed!
"I usually recommend Garden of Life, BioK or Megafoods brand," says Shapiro. "I also recommend starting with about 30 billion CFU and making sure your supplement has at least 12 different strains. And if you don't eat a diet high in fruits, vegetables, nuts, seeds, and whole grains that provide fiber for the probiotics to live off of, make sure you're the one you are taking contains prebiotics as well.
I didn’t know there was much of a difference between probiotics until I did some research. After realizing the ones I had been getting were probably not doing anything for me, I wanted to invest in a better option. This brand checked all the boxes and was still really affordable! I’ve been taking them for about a week now and I can tell a difference! The first few days I didn’t feel too great but realized it was because this probiotic was actually doing something for me and rebalancing my gut. Now I feel less bloated and all around healthier. I will definitely be getting more!

Best Probiotic says that Suprema Dophilus, manufactured and distributed by Vitabase, enjoys the highest customer rating in the market. Specially coated to help the bacteria spread through your entire digestive tract, its website claims over four billion viable cells per capsule, including five lactobacillus strains and three bifidobacteria cultures. Best Probiotic says that Suprema Dophilus also contains fructo-oligosaccarides to increase the life span of the bacteria.


Although most studies have shown few, if any, negative side effects, it is important to keep in mind that research on probiotics is still in a preliminary phase. There may be some risk for people who have certain health conditions. As with any supplement, it is essential that before you begin to take a probiotic supplement, that you speak with your physician first to help to ensure that you will not be putting your health at risk.


Fizzy, tangy, and even slightly vinegar-esque, kombucha has a cult following for a reason. The tea gets its natural carbonation from the "scoby" (that float-y thing you see in some bottled varieties), which is actually the bacteria and yeast that ferment the drink and creates the probiotics. "There's not much scientific evidence specifically on the benefits of kombucha, but it is another strategy to introduce more live, active bacteria into your lifestyle," says Palmer. Many are made with fruit juice for added flavor, so read the label to see what you're getting, she advises. Stick to store-bought kombucha; it's tough to keep the tea sanitary when you make it yourself, and homebrewed kombucha been linked to nausea and even toxicity. Also note that due to the fermentation process, kombucha contains trace amounts of alcohol, so it's best to stick to one 12-ounce bottle a day.

Pure Therapeutics Power Probiotic 100B offers 100 billion CFUs of 4 powerful probiotic strains, including science darling, the HN019 strain of Bifidobacterium lactis. Since environmental factors, including moisture, oxygen and heat, can degrade the stability of your probiotics, Pure Therapeutics 100B is delivered in nitrogen-purged aluminum blister pacts, which ensure viability until the probiotic hits your system. No refrigeration is required.
For most of my life, I thought of probiotics as something I’d only drink if I lost a bet. Then stress-induced irritable bowel syndrome (IBS) turned my intestinal tract into a nonstop river of shit—we’re talking weeks of everything I ate shooting straight out my butt in liquid form. The internet said probiotics were my best non-pharmaceutical bet to help my digestive system calm down, so I swallowed my pride (and my first kombucha ever) and kinda sorta saw the light. My IBS wasn’t cured, but probiotics did help me spend less time on the toilet wide-eyed with terror, and more time doing what’s really important in life—watching TV with my family.
Some studies suggest that certain probiotic strains may also help in mild to moderate ulcerative colitis and possibly for bloating and gas in irritable bowel syndrome (IBS). Probiotic supplements, on the whole, “improve global symptoms, bloating, and flatulence in IBS,” by modifying the gut microbiome, according to a 2014 monograph from the American College of Gastroenterology. As IBS researchers said in a paper in Gastroenterology & Hepatology in 2015, “The concept of manipulating the microbiome is one of the most promising new ways in which to treat patients with IBS, but there is still much to learn.”
The second Elinav study, “Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT” involved a mouse model and human patients. One cohort of mice and a parallel human group was given the same probiotic strain used in the first study to see if they had more success repopulating their gut microbiota after a round of antibiotics. Another “watch-and-wait” cohort didn’t take probiotics to assist gut microbiome recovery after antibiotic-related depletion. A third cohort was given an “autologous fecal microbiome transplant” (aFMT) which consisted of a patient’s own gut microbiota that had been collected before he or she started a cycle of antibiotics.
Probiotic bacteria actually compete against unfriendly flora for bacterial binding sites on the inside lining of your intestines, further protecting you from these harmful pathogens. One way to repopulate your gut with probiotics to restore harmony and get all their many benefits is with the right foods, which can support the growth and proliferation of good bacteria that crowd out the bad ones.
Then, study participants were divided into one group that consumed a standard probiotic strain available in commercial supplements and a control group that was given a placebo. After two months of treatment, the researchers found that some people were so-called “resisters” who expelled the gut microbiomes in probiotics; others were identified as “persisters” who successfully colonized the generic probiotic strains in their GI tracts.
As of now, the most comprehensive meta-study (a study of different studies) has not been able to decisively identify any particular strain of bacteria that is specifically useful to treat seasonal allergies. Some studies contradict each other on which bacteria can treat grass pollen, and other studies will find that those strains the first two studies examined weren’t nearly as effective in their own trials.
Unfortunately, many commercial brands don’t measure up. They are unstable in stomach acid. Quality control measures aren’t intact, including ensuring supplements have been handled correctly and maintain their freshness. Moisture slipping into probiotic supplements can reduce their efficacy. Companies that use bioshield capsules produce higher quality probiotic supplements that are able to endure the stomach acid, releasing their contents within the small intestine, where a more alkaline environment ensures the survival of the bacteria.
Scientists are investigating probiotics, and their combined effects, by trying to classify the probiotic benefits of ingesting specific probiotic strains and understanding their role in the digestive tract. At present, the methodological and ethical limitations of human studies still make it difficult to fully understand the mechanisms of action of probiotics, but some explanations are available. Nevertheless, benefits linked to the consumption of probiotic strains have already been suggested (e.g. helping to support the immune system, help support digestive health), and others are still being investigated.

In addition to the impact on our immune systems, our digestive systems are the second largest part of the neurological system. It’s called the enteric nervous system and is located in the gut. This is why it’s called the second brain — the gut is responsible for creating 95 percent of the serotonin and may have significant impact on brain function and mood.
Probiotics have also been researched for how they support the immune system. Studies suggest that probiotics can improve how the immune system functions such as by decreasing upper respiratory tract infections in adults and reducing the need for antibiotics. Studies in children show that a regular diet including probiotics reduces colds and flu-like symptoms and improves attendance in preschool and day care settings.
Even if some of the bacteria in a probiotic managed to survive and propagate in the intestine, there would likely be far too few of them to dramatically alter the overall composition of one's internal ecosystem. Whereas the human gut contains tens of trillions of bacteria, there are only between 100 million and a few hundred billion bacteria in a typical serving of yogurt or a microbe-filled pill. Last year a team of scientists at the University of Copenhagen published a review of seven randomized, placebo-controlled trials (the most scientifically rigorous types of studies researchers know how to conduct) investigating whether probiotic supplements—including biscuits, milk-based drinks and capsules—change the diversity of bacteria in fecal samples. Only one study—of 34 healthy volunteers—found a statistically significant change, and there was no indication that it provided a clinical benefit. “A probiotic is still just a drop in a bucket,” says Shira Doron, an infectious disease expert at Tufts Medical Center. “The gut always has orders of magnitude more microbes.”
After the antibiotics had cleared the way, the standard probiotics could easily colonize the gut of everyone in the second group, but to the team's surprise, this probiotic colonization prevented the host's normal microbiome and gut gene expression profile from returning to their normal state for months afterward. In contrast, the aFMT resulted in the third group's native gut microbiome and gene program returning to normal within days.
“If someone has disrupted his gut microbial balance, this is where a probiotic can be of benefit,” says Gail Cresci, PhD, RD, an intestinal microbe specialist with Cleveland Clinic’s Department of Gastroenterology, Hepatology and Nutrition. “But whether it’s really going to help and whether you’re taking the right one are the big questions out there.”
Though capsules are ideal for quick, convenient consumption, powdered products are a great choice for anyone who wants to mix their probiotics with shakes or smoothies. The Hyperbiotics Organic Prebiotic Powder is a totally taste-free prebiotic powder that has inulin, FOS, resistant starch, and dietary fiber to help keep your gut health in line. Unlike probiotics, prebiotics works to nourish and grow the bacteria that is already in your body. This supplement also has acacia fiber, which is said to help suppress appetite and reduce gas and bloating. You can take between one and three scoops of powder a day, depending on how much microbial support you’re looking for. Each container comes with 375 grams or roughly 54 servings, and it doesn’t need to be refrigerated.

Remember that dietary supplements are not tested by the U.S. Food and Drug Administration like medications. And the probiotic strains in the supplements may not be specific for the condition you're looking to treat. You may want to consult with a practitioner, like a registered dietitian, who is familiar with probiotics. Always tell your physician what you are doing that may affect your health.
Given that you can get probiotics from the food you eat, you don't necessarily need to take a supplement, and Keatley says she prefers food sources of probiotics to supplements. However, she adds that "There are times when you really need a boost." One example might be during or after a course of antibiotics, as long as you have your doctor's OK, since antibiotics kill both good and bad bacteria: "Seeding your gut with good bacteria can lay the groundwork for a faster recovery and less constipation and diarrhea," Keatley points out. Angelone echoes Keatley's emphasis on food sources of probiotics, but also says that supplements can also play a useful role in "maintaining a healthy gut bacteria colony."
To factor strain-specific benefits into our efficacy score, we referenced the information in these guides. Products were rewarded for containing strains on these lists. Additionally, measured levels of each strain were compared to what is thought to be effective based on these guides, and scores were scaled accordingly. In cases where products did not list strain-specific amounts, or their listed strains were not included in these guides, total measured CFUs were compared to a general effectiveness threshold of 1 billion CFUs cited by research published in the American Journal of Clinical Nutrition11.
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