Probiotics are being used with increasing frequency as a treatment for several medical conditions, such as allergic diseases (atopic dermatitis, possibly allergic rhinitis), bacterial vaginosis, urinary tract infections, and prevention of dental caries or respiratory infections. Probiotics are used as a treatment for a variety of gastrointestinal (GI) disorders. In this review, the historical perspectives, proposed mechanisms of action, formulations and delivery systems, safety, and specific GI disorders for which probiotics have been used are discussed.
In the past, probiotics have been proposed as part of a weight loss diet. However, a 2015 meta-analysis looked at available randomized, controlled trials investigating this effect and determined that the studies did not seem to support this hypothesis, as body weight and BMI were not consistently reduced. The researchers did point out the need for better designed trials, because they were not convinced the results were based on well-designed science.
Probiotics act by stimulating the growth of microorganism colonies in our bodies that are “good” or helpful. These beneficial bacteria play an important role in maintaining the natural balance in our systems, stabilizing our digestive organs’ barriers against undesirable microorganisms, producing substances that inhibit “bad” microorganisms’ growth, outcompeting undesirable microorganisms, and stimulating immune responses.1
"Want to feel happier, get off SSRIs? You have to mind your gut," I told Dawn before explaining the often-overlooked gut-brain connection. It isn’t just depression that gut health affects but headaches, migraines, allergies, autoimmunity, weight gain, acne, skin rashes, yeast infections, hormonal imbalances, fatigue, immune challenges, and even the way you sense pain can be linked to your gut health. So as a medical doctor who specializes in gut health, when I say things start in your gut—I really mean it!
The U.S. Clinical Guide to Probiotic Products1, Canadian Guide to Probiotic Supplements2 and the WGO Global Guidelines for Probiotics and Prebiotics3 provide suggested effective amounts of specific strains for treating certain health conditions, such as constipation or IBS. All 37 products listed the species of bacteria they contained, but only 14 listed amounts of individual strains. We found that 9 of those 14 products provided beneficial bacteria at effective levels. The Center for Responsible Nutrition recommends4 the industry move toward specifying strains as a best-practice because whether a product works and for what purpose depends on its strains. 

A probiotic dietary supplement can aid your health in a variety of ways. Lactobacillus species, Bifidobacteria, Saccharomyces boulardii and Bacillus coagulans are the most common beneficial bacteria used in probiotic dietary supplement products. But each type — and each strain of each type — can work in different ways. Bottom line: Not all probiotics are the same, nor do they all have the same effect in the body.
The gut microbiota has been implicated in diseases ranging from obesity to Parkinson's disease and depression. Little wonder then that commercial probiotics have gained widespread popularity and are now estimated to command a US$37 billion market worldwide. But with research into the microbiome still in its infancy, increasing evidence suggests that both commercial and clinical use of probiotics is outpacing the science.
Contrasting antibiotics, probiotics were defined as microbially derived factors that stimulate the growth of other microorganisms. In 1989 Roy Fuller suggested a definition of probiotics that has been widely used: "A live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance."[61] Fuller's definition emphasizes the requirement of viability for probiotics and introduces the aspect of a beneficial effect on the host.

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."
Infectious diarrhea in both adults and children may be shortened by the use of probiotics [Allen et al. 2004]. The duration of symptoms is decreased by about 30 hours as suggested by a systematic review of trials in active infectious diarrhea. In this Cochrane review, 23 studies including almost 2000 participants (352 of which were adults), it was concluded that probiotics reduced the risk of persistent diarrhea compared with placebo or no probiotics at 3 days with a RR of 0.66 (95% CI 0.55–0.77) [Allen et al. 2004]. The majority (18 out of 23 studies) of the probiotics tested were LABs with two studies using S. boulardii.
Like kefir, kombucha is a fermented drink that may improve the function of the immune system and boost energy levels and detoxification. Beneficial bacteria in kombucha may improve antioxidant activity in the body as well. Kombucha tea comes in black and green varieties. Kombucha tea is made using a SCOBY, or a symbiotic colony of bacteria and yeast, that is necessary for the fermentation process. Saccharomyces boulardii is a probiotic yeast strain that is found in kombucha.
Reviews looking at the treatment or prevention of vulvovaginal candidiasis in women, pneumonia in patients hooked up to respirators, and colds in otherwise healthy people show some positive results. But the authors note that the studies are almost all of low quality, small in size, and often funded by companies with significant conflicts of interest.

More than 80 years later, probiotics have become wildly popular and incredibly profitable. A 2012 survey by the National Institutes of Health showed that 3.9 million Americans stated they had used some form of probiotics or prebiotics (a type of dietary fiber thought to feed the friendly bacteria in your gut) in the last 30 days—3 million more people than in the previous study in 2007. Probiotics are now available for consumption in almost every imaginable form—pills, tablets, yogurts, juices, cereals, and energy bars. They have been touted as having benefits not only for digestive health, but also mood disorders, cancer, cold and flu prevention, and reproductive health issues.
Make sure to keep probiotics away from moisture and heat, which can kill off some of the microbes. I recommend taking them on an empty stomach, ideally right when you wake up. You should always store supplements in a cool, dark place. Most strains of probiotics are fragile and should be protected from heat, so refrigeration is ideal. I recommend the probiotic Gut Instinct from HUM Nutrition for transparency and high quality.
Many avenues of research have examined probiotics benefits for skin, especially in children. Meta-analyses have found that probiotic supplements are effective in the prevention of pediatric atopic dermatitis and infant eczema. The integrity of gut bacteria is also connected to the development of acne, although the way this happens is still unclear.

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.
The other way that probiotics help is the impact that they have on our immune system. Some believe that this role is the most important. Our immune system is our protection against germs. When it doesn't function properly, we can suffer from allergic reactions, autoimmune disorders (for example, ulcerative colitis, Crohn's disease, and rheumatoid arthritis), and infections (for example, infectious diarrhea, H. pylori, skin infections, and vaginal infections). By maintaining the correct balance from birth, the hope would be to prevent these ailments. Our immune system can benefit anytime that balanced is restored, so it's never too late.
In a separate study involving 21 healthy volunteers, also published today in Cell, the same group of researchers found that taking probiotics after treatment with broad spectrum antibiotics may actually delay the return of people's normal gut microbiome. This goes against the idea that probiotics can help "repopulate" people's gut bacteria after antibiotics wipe them out.
Although many manufacturers will make claims regarding the benefit of probiotics for all sorts of disorders, there is not always research to back up those claims. It can be difficult to conduct quality research on probiotics due to the wide variety of strains available. And many studies show mixed results. However, given that, there is some research support for the use of probiotics for the following health conditions:
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Made from fermented cabbage and other vegetables, sauerkraut is not diverse in probiotics but is high in organic acids (what gives food its sour taste) that support the growth of good bacteria. Sauerkraut is extremely popular in Germany today. It is high in vitamin C and digestive enzymes. It’s also a good source of natural lactic acid bacteria, such as lactobacillus.

Officials in the E.U., where supplements are more heavily regulated than in the U.S., haven't authorized the use of the word probiotic to back any health claim. The only approved use related to microorganisms is "live yogurt cultures and improved lactose digestion." It can all feel like, well, a punch to the gut. So we asked scientists at the forefront of probiotic research to help us separate fact from hype, and pros...from cons. Here's what you need to know.
Probiotics are being used with increasing frequency as a treatment for several medical conditions, such as allergic diseases (atopic dermatitis, possibly allergic rhinitis), bacterial vaginosis, urinary tract infections, and prevention of dental caries or respiratory infections. Probiotics are used as a treatment for a variety of gastrointestinal (GI) disorders. In this review, the historical perspectives, proposed mechanisms of action, formulations and delivery systems, safety, and specific GI disorders for which probiotics have been used are discussed.
Because chronic inflammation is at the root of many diseases and health conditions, the fact that probiotics exert this effect in the gut, where 80 percent of the immune system lies, is crucial. The immune-boosting benefits of probiotics seem to be particularly helpful for the quality of life of seniors. Currently, research is underway to test whether probiotics can “reduce inflammation and improve gut immune health in HIV-positive individuals” who haven’t yet undergone treatment.
While the logic behind probiotics might seem sound, it is clear that we have a long way to go before understanding the complexity of the microbiota and the effects—both good and bad—that probiotics might have. All individuals have a unique gut microbiome, and the effects of different bacteria on different people are likely to be highly variable; as such, probiotic use might even need to be personalised for optimal benefits. Commercially available products might not contain the correct strains or quantities of bacteria to provide benefits, and most probiotic supplements contain only single strains, vastly oversimplifying the complexity of the microbiota. While taking a supplement for improved health is certainly an attractive prospect, those looking to aid their gut microbiota might be better served by consuming a healthy, varied diet. In the meantime, rigorous clinical trials are needed to substantiate potential health benefits and to confirm whether probiotics are elixirs or just empty promises.