They probably are. Lebwohl says probiotics may decrease the risk of getting diarrhea during the course of taking antibiotics, and may also play a role in specifically preventing the development of the dreaded antibiotic-related super diarrhea called C. difficile or C. diff. Antibiotics can wipe out the good bacteria that keep you from getting sick if you’re exposed to C. diff, or if you already have it in your system. C. diff symptoms can range from a moderate watery diarrhea several times a day to severe infections, which can be accompanied by fever, bloody stools, rapid heart rate, and can even lead to kidney failure. 500,000 Americans were infected with C. diff in 2015 and 15,000 died from it.
The current probiotic push lends itself to the question, "If humans got along fine without taking a probiotic supplement for thousands of years, why are they so important now?" Although there is no definitive answer to this question, there have been some significant cultural changes that have had an impact on the gut flora (the population of organisms that populate our intestines). These include the use of antibiotics, diets lacking in gut-healthy plant food, refrigeration and improved sterilization of foods. What we don't yet know is true is if probiotics actually turn around these changes and support the health of your gut flora.

Don't assume that the only way you can get your probiotic yogurt fix is through dairy. Cultured soymilk, or soy yogurt, is a non-dairy alternative that also boasts live active cultures. Most of these products are fortified with calcium and vitamin D to make them comparable to dairy yogurts. It makes a great option if you're vegan or lactose intolerant. (And if you're looking for more variety, almond milk and coconut milk yogurts are also rich in probiotics.)
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.”
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.

​​​​​​AZO Complete Feminine BalanceTM is a daily probiotic supplement designed for the unique needs of women. Researchers that formulated the blend started by selecting species that are dominant in the healthy vaginal microbiota. Then they further refined the formula by selecting strains of probiotics that flourish in the vagina. The blend is clinically proven to help protect vaginal/feminine health.*
Both probiotics and prebiotics are a continuing topic of research regarding immunity. When used in conjunction, scientists refer to them collectively as synbiotics. One 2015 review on the subject stated, “We suggest that LAB and Bifidobacteria and novel strains [of probiotics] might be an additional or supplementary therapy and may have potential for preventing wide scope of immunity-related diseases due anti-inflammatory effect.”
To boost the immune system, B. Lactis is a promising choice. One study had participants taking either a probiotic or a placebo for 6 weeks. At the end of the period, researchers measured antibody levels and found greater increases in antibodies of the B. Lactis group than in placebo participants, concluding that this probiotic may help improve immune function [1]. In addition, a 2009 study found that supplementation of the strain B. Lactis DN-173 led to self-reported improvements in digestive comfort [2].

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.
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.
Quality matters for any supplement, and that goes triple for probiotics. Many commercial brands lack the technology to identify specific strains and how much of that strain each dose contains. That could mean you get an ineffective or potentially harmful dose. It's a great sign if the company is using strains that have been used specifically in clinical trials at a dose similar to or the same as that used in the study. This is one of the only ways to guarantee a probiotic's clinical effectiveness.
If you've ever been to an Indian restaurant, then you've probably seen a lassi—a smoothie made of milk, yogurt, fruit, honey, and cardamom. The drink goes well with spicy Indian food because it helps extinguish the fiery feeling in your mouth. If you want to try it at home, you can pick up bottles from brands like Dahlicious, which contain 15 billion live probiotics per serving and are available in flavors like mango and turmeric. Or, try this mango lassi recipe.
Cleaning up your diet to remove things that bother you and to add nutrients you and your microbiota need, physical activity to reduce stress and increase feel-good neurotransmitters, mindfulness to discover how your thoughts affect your feelings, and daily consumption of probiotic pills and foods are easy ways to improve your mental health outlook.