While one 2009 study did show some evidence for reducing cold and flu symptoms in children ages three to five and a 2015 analysis showed probiotics to be better than placebo in preventing acute upper respiratory infections, neither were enough to convince the National Institutes of Health of the efficacy of probiotics for colds and flu. The NIH confirms, “the evidence is weak and the results have limitations.”
Although some probiotics have shown promise in research studies, strong scientific evidence to support specific uses of probiotics for most health conditions is lacking. The U.S. Food and Drug Administration (FDA) has not approved any probiotics for preventing or treating any health problem. Some experts have cautioned that the rapid growth in marketing and use of probiotics may have outpaced scientific research for many of their proposed uses and benefits.

"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.


A popular dish in Japan consisting of fermented soybeans, natto contains the extremely powerful probiotic bacillus subtilis, which has been proven to bolster your immune system, support cardiovascular health and enhance digestion of vitamin K2. Natto can also contain vitamin B12, which is usually lacking in vegan diets. It’s also one of the highest plant-based proteins.

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.
“Microbiome” refers to the trillions of bacteria and microorganisms that live on and in our individual bodies. “There’s increased recognition of the various ways that the microbiome affects our health,” Lebwohl tells me. “And with that recognition comes the true observation that many bacteria are good for us. This goes against the old idea that bacteria equal germs, which equal harm. It turns out that many bacteria keep us healthy and probiotics could potentially support that notion.”

​​​​​​Lactobacilli dominate a healthy vaginal microbiota. Menstrual cycles, sexual activity, diet, certain medications, hygiene, and other factors can occasionally disrupt the vaginal microbiome. AZO Feminine Balance Daily Probiotic has been clinically demonstrated to contribute to the colonization of these important lactobacilli in the vagina.* The result: restoring the natural balance of good bacteria and yeast to maintain vaginal health.*
Minerals And Extracts – Many probiotics, especially those marketed for women, also contain blends of vitamins, minerals, and plant extracts for optimal results. In some cases, these blends can be so inclusive that they actually replace your traditional multi-vitamin, and can be an excellent source of nutrition for women that don’t receive enough vitamins or nutrients in their basic diets.
This Korean staple relies on lactic acid fermentation (also called lacto-fermentation) to turn cabbage or other vegetables into a spicy, pungent side dish that's packed with vitamin C. Order it at Korean restaurants or buy it in the refrigerated section of your grocery store (King's Kimchi is widely available at Walmart). For some guidance on making your own, turn to The Art of Fermentation ($23; amazon.com). Then, use it to spike veggie-laden rice bowls, top on soup, or serve alongside meat.
Probiotics and raw fermented foods and drinks, such as sauerkraut and kefir that contain probiotic-like microbes, are very helpful for digestion. They help to keep your gastrointestinal tract at the proper pH for optimal digestion and help to break down foods. They also regulate the motion of your intestines so that food moves through at the proper pace.
Further, there’s still a lot we don’t know. A recent study published in Cell compared how the microbiome of the gut reconstituted itself after antibiotic treatment with and without probiotic administration. The researchers found that probiotics (which might have improved diarrhea symptoms) led to a significant delay in microbiome reconstitution, if it occurred at all. And — again — this study was with purified strains of bacteria, which is not what you’re getting in probiotic-containing food.
You also want to look at the guarantee fine print: If the CFU number is guaranteed at time of manufacturing, but not at the time of expiration, you could be taking a less potent dose of probiotics than you think because potency fades over time. I made this mistake when I was traveling once and went to the grocery store to pick up probiotics. On the bottle label it said guaranteed at 20 billion CFU at the time of manufacturing. This doesn’t tell you the CFU for when I was actually taking the probiotics. For instance, our probiotics are manufactured at 60 billion and 200 billion CFU, and guaranteed at 30 billion and 100 billion CFU, respectively, at time of expiration.
Another study by Elinav and his colleagues suggests that not everyone’s gut reacts the same way to probiotic pills. They studied samples of microbiomes from antibiotic users before and after they took supplements for four weeks. The good bacteria were found in the digestive tracts of some people. But in others, the bacteria were present only in stool samples, not in their digestive tracts, where they’re thought to be needed to improve health.
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Many wondered whether probiotics could be therapeutic in other gastrointestinal disorders. Unfortunately, that doesn’t appear to be the case. Probiotics didn’t show a significant benefit for chronic diarrhea. Three reviews looked at how probiotics might improve Crohn’s disease, and none could find sufficient evidence to recommend their use. Four more reviews looked at ulcerative colitis, and similarly declared that we don’t have the data to show that they work. The same was true for the treatment of liver disease.
Consuming probiotics regularly will reduce the risk of this. "The concept is that if we have an unhealthy, unbalanced gut environment, toxins can be released into the bloodstream and cause inflammation throughout the body," Engelman adds. "This shift in gut flora and the subsequent inflammation can cause a flare-up in the skin of those who are predisposed to acne, eczema, or rosacea."
EDITOR’S CHOICE: As the only probiotic formula we reviewed backed by a New York Times Bestselling author and expert in the human biome, the Garden of Life Dr. Formulated Once Daily Women’s Probiotic is our top choice for overall digestive and women’s health. With 50 billion cultures and 16 probiotic strains, this probiotic helps to promote women’s digestive, immune and vaginal health.
CFU: This is the number of "colony forming units" present in each dose, which are measured in the billions. And while more isn't always better, "you want at least 20 to 50 billion CFU," says Dr. Nazareth. Just for reference, a very high dose is 400 CFU, which most experts agree is not necessary unless your health care practitioner specifically recommends this for you. It's also important to check for the guaranteed CFU upon expiration, which should be listed clearly. "Some products only guarantee the CFU number at the time of manufacturing, therefore will be less potent by the time the product reaches your home," she says.
Of course, your gut microbiome can only do this when it’s healthy and in balance, which is where probiotics come in. Since so many factors can deplete your beneficial bacteria—including everything from exposure to antibiotics in food or medication to spending too much time inside—supplementing with a premium probiotic is almost always necessary to maintain balance.
We also found strains linked to five other health benefits like weight loss and lowering cholesterol. We feature options for those cases below, but they aren’t top picks because those use cases aren’t as heavily researched as immune health or IBS relief. Still, chances are any probiotic supplement is going to make some improvement to your digestive health, so don’t be afraid to experiment.

What about prebiotics vs probiotics? Prebiotics are the food fibers that go through the gut unchanged and are then used by good colon bacteria as a food source for their own growth. Everyone already has most of these good bacteria present, but often in small quantities. Prebiotics are used to stimulate their growth. Simply stated, you already grow your own probiotics within your colon. You do not rely on them to make the passage through the stomach acid — acid that can destroy many probiotic bacteria. That’s why taking a probiotic supplement or adding probiotic foods to your diet does not always help your digestive system. You can eat as many probiotic bacteria as you want, but if they don’t survive the trip to the colon, your effort will be fruitless.
Made by fermenting the juice of young coconuts with kefir grains, this dairy-free option for kefir has some of the same probiotics as traditional dairy kefir but is typically not as high in probiotics. Still, it has several strains that are great for your health. Coconut kefir has a great flavor, and you can add a bit of stevia, water and lime juice to it to make a great-tasting drink.
My husband is battling lung cancer and Sarcoma and has a lot of gut issues such as nausea and vomiting which have caused him to lose a significant amount of weight. To help with the N/V a probiotic was recommend. I’d like to try him on the BlueBiotics Ultimate Care but am concerned that by doing so it will cause him to lose even more weight which he has no extra weight to spare. What are your thoughts on this?
Experts agree that this is the most important factor to consider in choosing a probiotic. "You should absolutely choose a probiotic based on what you are looking to address," says Chang. "Because strain specificity will impact outcomes, it is important to consider that one strain that works for one condition will not necessarily be effective for other conditions."
Jotham Suez, Niv Zmora, Gili Zilberman-Schapira, Uria Mor, Mally Dori-Bachash, Stavros Bashiardes, Maya Zur, Dana Regev-Lehavi, Rotem Ben-Zeev Brik, Sara Federici, Max Horn, Yotam Cohen, Andreas E. Moor, David Zeevi, Tal Korem, Eran Kotler, Alon Harmelin, Shalev Itzkovitz, Nitsan Maharshak, Oren Shibolet, Meirav Pevsner-Fischer, Hagit Shapiro, Itai Sharon, Zamir Halpern, Eran Segal, Eran Elinav. Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT. Cell, 2018; 174 (6): 1406 DOI: 10.1016/j.cell.2018.08.047
Self-dosing with bacteria isn't as outlandish as it might seem. An estimated 100 trillion microorganisms representing more than 500 different species inhabit every normal, healthy bowel. These microorganisms (or microflora) generally don't make us sick; most are helpful. Gut-dwelling bacteria keep pathogens (harmful microorganisms) in check, aid digestion and nutrient absorption, and contribute to immune function.
Next time you pack your travel beauty bag, slip a shelf-stable probiotic in there to preempt bathroom emergencies, Fasig says. Look for one that contains Lactobacillus acidophilus, Lactobacillus sporogenes, Bifidophilus bifidum, and Sacchromyces boulardii strains ($20, amazon.com), which Fasig says can improve your intestinal health to fix issues with constipation or diarrhea.
Despite the uncertainty, foods enriched with probiotics and probiotic supplements are increasingly popular in the U.S. Finding probiotic supplements in grocery and health food stores is easy. For example, you may already know that yogurt contains probiotic bacteria such as lactobacillus and bifidobacteria. Many clinical studies suggest these bacteria relieve symptoms related to lactose intolerance.
Jotham Suez, Niv Zmora, Gili Zilberman-Schapira, Uria Mor, Mally Dori-Bachash, Stavros Bashiardes, Maya Zur, Dana Regev-Lehavi, Rotem Ben-Zeev Brik, Sara Federici, Max Horn, Yotam Cohen, Andreas E. Moor, David Zeevi, Tal Korem, Eran Kotler, Alon Harmelin, Shalev Itzkovitz, Nitsan Maharshak, Oren Shibolet, Meirav Pevsner-Fischer, Hagit Shapiro, Itai Sharon, Zamir Halpern, Eran Segal, Eran Elinav. Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT. Cell, 2018; 174 (6): 1406 DOI: 10.1016/j.cell.2018.08.047
Although some probiotics have shown promise in research studies, strong scientific evidence to support specific uses of probiotics for most health conditions is lacking. The U.S. Food and Drug Administration (FDA) has not approved any probiotics for preventing or treating any health problem. Some experts have cautioned that the rapid growth in marketing and use of probiotics may have outpaced scientific research for many of their proposed uses and benefits.
Hi Joan, it’s possible, but not ideal because most pill form probiotic supplements are designed to be protected from stomach acid until the capsule reaches the intestines. It’s impossible to say how many probiotic microorganisms would survive by taking them this way, but certainly less than if you swallow the pills. I would recommend trying a probiotic gummy product or some other probiotic that comes in something other than pill form rather than opening up the capsules.
Women’s health expert Dr. Amy Myers is a goop-trusted authority on subjects from autoimmunity and Candida to thyroid dysfunction; and she’ll be speaking IRL at our first wellness summit on June 10. Here, Myers helps us evaluate the increasing buzz around probiotics, and outlines the ins and outs of selecting a particular supplement (whether hers or other brands). Plus, we’ve rounded up our probiotic essentials, from inner beauty powders to favorite fermentation recipes, in one guide:
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