You’ve probably heard the term “probiotics” thrown around in your doctor’s office or grocery store, especially regarding some staple foods in your kitchen, including yogurt, kefir, and kimchi. You might’ve also caught wind that probiotics are living microorganisms (including common bacterial strains like Lactobacillus and Bifidobacterium as well as yeast), but not the scary kind that make you sick. It’s the opposite: Probiotics support proper body function by stimulating the immune system, promoting digestion, inhibiting growth of potentially harmful bacteria that lead to infections, and producing key nutrients, such as B vitamins and folate. That’s not all: Probiotics have also shown to alleviate diarrhea and constipation, decrease the duration of colds, aid weight loss, and lower cholesterol and blood pressure levels.

While researchers have proven over the last two decades through 6000+ studies (60 percent of which were published in the last five years) that these invisible-to-the-naked-eye organisms are good for your health, it’s still unclear which probiotics to consume to reap the most rewards. Though fermented foods are nothing new—they’ve been around for more than 7,000 years, starting with fermented fruits, milk (aka kefir), meats, pickled vegetables, bread, beer, and wine —which are the best is still a mystery. What’s more confusing is that shelves are being stocked with more probiotics-infused products—including frozen burritos, cold-brewed coffee, even protein powder—plus supplements than ever before.


Related: Should You Be Eating More Fermented Foods?


“With food sources versus supplements, there’s more potential to buy a product that doesn’t contain probiotics—or if it does, those probiotics may not be viable,” says Lynne V. McFarland, Ph.D., affiliate associate professor in the department of medicinal chemistry at the University of Washington and co-author of The Power of Probiotics: Improving Your Health with Beneficial Microbes. “There is no quality control for the efficacy of probiotic strains in most grocery store foods.”

This is exactly why experts say it’s important to choose a brand that’s transparent about any probiotic strains present. “It takes a great deal of product development to ensure the survival of probiotics in processed foods, but it has been done successfully,” says Wendy J. Dahl, Ph.D., associate professor of food science and human nutrition at University of Florida. “Some processed foods have quite ingenious ways of probiotic administration—for example, probiotics in the straw of a beverage and probiotics in yogurt-flavored balls in breakfast cereals.” When foods are pasteurized, as with yogurt or baked, the probiotic would have been killed due to heat, but may have been added back in after heating. This is possibly the case with foods such as the aforementioned burrito.

“Even established food manufacturers often do not have the quality control to ensure consumers that the probiotic strain listed on the label is really in their food product,” McFarland says. For example, some yogurts that use live cultures of bacteria in the fermentation process may not actually contain probiotics. “Typically yogurts only contain Streptococcus thermophilus or Lactobacilli bulgaricus strains used to start the fermentation of yogurt,” McFarland says. “These two strains do not have any probiotic properties and are not probiotics.”

As a general rule of thumb, if the yogurt label lists strains other than the starter bacteria, it may contain probiotics. Dairy brands that do feature probiotics, like the yogurt Activia and dairy drink Yakult, have proven to help with constipation. The drink DanActive also contains probiotics that may prevent pediatric diarrhea.

As for probiotic supplements, only go with brands that have passed stability tests. “Clinical trials have shown effective results for some specific strains regardless if they are given in yogurt, fermented beverages, or in capsules,” McFarland says. “If stability tests prove that the dose of required probiotic strains survive the shelf-life of the food or yogurt, then these products are as good as probiotic strains in pills or capsules.” (Check out this review of 42 probiotic products on ConsumerLab.com).

The tricky part with these pricey pills is that you’ve got to take many probiotics with food to protect them from being destroyed by stomach acid. Also, you have no way of knowing if the probiotics in the supplement are potent. “Supplements can be fine, but there is a risk they were not shipped or stored properly,” says Tod Cooperman, M.D., president of ConsumerLab.com. “This risk is much lower with yogurts and kefirs, since they are required to be kept refrigerated.”

Bottom line: You may be better off eating probiotic-containing foods and skipping the supplements. “[Foods containing probiotics] last through the entire digestive system and do not get killed off in the stomach,” says Rebecca Lee, R.N., founder of the natural-healing website RemediesforMe.com.

Learn more about the benefits of probiotics in the video below.

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