“Many fermented foods are made with the help of bacteria, so it’s tempting to think that they all contain probiotics,” says Ali Webster, PhD, RD, director of research and nutrition communications at the IFIC. “But that’s not the case: In order for a food to be considered a source of probiotics, there needs to be enough live bacteria that survive food processing, which doesn’t always happen with fermented foods. Further, any bacteria that survive food processing must be known to benefit human health.”
Just because not all fermented foods have probiotics, however, doesn’t mean you need to cross the entire category off of your list of gut-healthy foods. Quite the contrary. Instead, you just need to know which ones do and don’t contain probiotics or are otherwise good for your gut, something Dr. Webster helps break down below.
The difference between fermented foods and probiotics
“One of the most common misconceptions I encounter is the belief that fermented foods and probiotics are one and the same,” Dr. Webster says. Fermented foods are made through a process that uses yeast and live bacteria to break down one food, like cabbage, for example, and turn it into another, such as sauerkraut or kimchi. Meanwhile, probiotics are the yeast and bacteria used to ferment food. They also exist naturally in your body, but sometimes the balance between good and bad bacteria in your gut can get thrown off by what you eat or drink, as well as your lifestyle—lack of sleep being one such culprit.
So to help support their microbiome (the collection of bacteria and organisms that lives in your G.I. tract) people may turn to foods and supplements that contain probiotics to try and bring their gut flora back into balance. “Probiotics do have potential for positively impacting health, and different mechanisms for doing so are an active area of research,” Dr. Webster says. The connection, though, is still unclear and further adds to the confusion between probiotics and fermented foods.
"We know that probiotics are helpful for gut health, which is why many assume that fermented foods would be beneficial also; however, there isn't enough research to actually make this claim," Natasha Bhuyan, MD, a doctor at OneMedical, previously told Well+Good. What’s more, science isn’t entirely sure why fermented foods are good for gut health. It may be their probiotics, but it may not. “Some precursors to fermented foods like cabbage and other vegetables are rich in fiber and act as prebiotics,” Dr. Webster says. “Fiber serves as food for the beneficial bacteria in our gut and results in production of short-chain fatty acids that fuel the cells lining the intestines and maintain gut health.”
Above and beyond probiotic activity, though, fermented foods offer a wealth of benefits, according to Dr. Webster. “Yogurt and kefir are rich in protein and calcium,” she says, adding that fermented foods are also chock full of many vitamins, minerals, and other nutrients. “They contribute unique flavors to our meals and in many cases are a big part of the cultural aspects of food and food traditions,” Dr. Webster adds. All the more reason to keep them in your dietary rotation.
Fermented foods with probiotics
Some fermented foods have demonstrated probiotic capabilities and associations with reduced inflammation and improved gut health, according to Dr. Webster. “Dairy products like kefir and yogurt are among the best vehicles for delivering beneficial bacteria to our gastrointestinal tract,” she says. “Non-heated kimchi, sauerkraut, and miso also contain large numbers of viable bacteria that can provide a probiotic boost. However, many varieties of these products found on grocery store shelves have been heat-treated for food safety reasons, so it’s not as common to come across options with known probiotic activity.”
Fermented foods that don’t contain probiotics
As you now know, not all fermented foods contain live organisms. “Microbes that are essential for making beer and wine are filtered out in the finished product,” Dr. Webster says. “Sourdough breads and canned sauerkraut, other fermented vegetables, and many kombuchas are heat-treated, which inactivates the microorganisms. So even though these products might taste good and offer some nutritional benefits, they’re not strong sources of probiotics.”
Best practices for eating probiotic products (fermented or otherwise)
There is no recommended daily allowance for probiotics, Dr. Webster says. “What we do know is that in order to reap benefits from probiotic products, they need to be consumed with some degree of regularity. A cup of yogurt once in a while or a few spoonfuls of kimchi with your takeout probably aren’t going to make much of a sustained impact on gut health, even if they offer other health and nutrition benefits.”
The best way to reap benefits from probiotic products, then, is to eat them regularly. “Maintaining a continual presence of probiotic microbes requires repeatedly re-introducing them—by making yogurt part of your daily eating pattern, for example,” Dr. Webster recommends.
But even then, there’s no guarantee that it’ll do much for your gut. “At this point, it’s unclear if probiotics from food can truly take root in an already-crowded microbial landscape,” says Dr. Webster. “Think about it: If millions of gut bacteria have already staked a claim to all of the available real estate, it’s pretty tough for new ones to find their own patch of land.”
That said, diet is only one way to improve and support your gastrointestinal system. Staying hydrated, minimizing stress, and moving your body are other gut-healthy habits you’ll want to adopt.
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