Fermented foods are trending, despite having been around for literally thousands of years. Then again, nutrition trends are often anything but new. (See: intermittent fasting, fibermaxxing, and magnesium supplements.) Regardless, gut-friendly foods like sauerkraut, kimchi, and yogurt seem to be more popular than ever before. Biohacking podcaster Andrew Huberman talks about them constantly. They’re a key part of longevity influencer Bryan Johnson’s Don’t Die protocol. And last month The Wall Street Journal reported that several key government officials, including Health Secretary Robert F. Kennedy Jr. and Vice President JD Vance, have recently gone all in on fermented foods. (Earlier this year the Trump administration also added fermented foods to the USDA’s dietary guidelines for the first time ever.) But why all the hype, and why now?
What are fermented foods?
Fermented foods are simply ordinary foods, such as fruits, vegetables, and dairy, that have undergone fermentation—a natural process by which microorganisms like yeast and bacteria convert carbohydrates into acids, gases, and other by-products. Cabbage becomes sauerkraut or kimchi. Milk becomes yogurt or kefir. And so on.
Historically, fermentation was used out of necessity, as a preservative measure for extending the shelf life of various foods. Fermentation can also transform how foods taste, giving them a tangy or funky flavor, similar to pickling. But the recent hype around fermented foods has nothing to do with either of these, and everything to do with their potential health benefits. “The compounds that are created during fermentation have also been shown to influence health by regulating inflammation,” says registered dietician Hennis Tung, MS, RD. “They create a more favorable gut environment, and greater gut microbial diversity is linked to better health in general.”
Why are fermented foods trending?
Obviously, when a high-ranking White House official starts stuffing sauerkraut into his wife’s Chanel bag on the way to dinner, people are going to talk about it. But that’s not why you should care about fermented foods right now. Rather, the reason these types of foods should be on your radar is that the research is starting to confirm what the experts (and, yes, the longevity bros) have been saying for years: These foods are incredibly good for you. “The science has finally caught up with how central the gut is,” says Johnson. “Once you start seeing the gut as an organ you can feed and shift, fermented foods stop looking like a wellness fad and start looking like an input you can measure.”
In a 2021 trial published in the journal Cell, Stanford researchers observed that when healthy adults ate a diet rich in fermented foods for 10 weeks, blood levels of inflammatory markers were significantly lower than that of a control group that ate nonfermented (but still good-for-you) fiber-rich foods. By the end of the study, the group that ate fermented foods had also developed considerably more diverse gut microbes. A 2023 study published in The Journal of Nutrition surveyed the dietary habits of thousands of Americans and revealed that microbe-containing foods improved a whole range of health outcomes, from blood pressure to waist size. Most recently, a 2025 review published in the journal Foods declared fermented foods to be “a strategic dietary intervention for microbiome modulation and health promotion.”
As the research continues to compound, more fermented products, such as sauerkraut and kimchi, are making their way into grocery stores to meet increasing demand. "We’re seeing demand growing pretty much across the board for fermented products—specifically sauerkraut, kimchi, and fermented pickles,” says Jorge Azevedo, CEO of Fermented Food Holdings, the parent company of brands that include Wildbrine and Bubbies. “This type of ramp-up in academic production doesn’t happen unless scientists are finding confirmation of prior research,” Azevedo says. “We now have a much stronger understanding of what it is that fermentation does to people’s health, and how it does it.”
What are the actual benefits of consuming fermented foods?
The microbes in fermented foods are typically credited with improving gut health. While that is true, what’s important to understand is that gut health is a precursor for full-body health. “Gut health is not just isolated to the gut itself,” says Tung. “It’s linked to pretty much everything in the body—your brain, your immunity, your skin, your organs. And when we talk about inflammation regulation, that’s tied to your blood sugar control, your weight, and even your mental health.” Kennedy claims to have lost 20 pounds in 30 days as a result of switching to a diet consisting primarily of fermented foods and grass-fed beef. “JD Vance is also on the diet, and you can see how different he looks,” Kennedy said at an event in Michigan last month. (Though, to be clear, we do not know the actual diet of these men, or what other potential weight-loss medications they may be on.)
According to Sean O’Mara, MD, the doctor credited with turning Kennedy and Vance, along with Commerce Secretary Howard Lutnick and Transportation Secretary Sean Duffy, onto fermented foods, weight loss is one of the most noticeable results his clients see when they add fermented foods to their diets—along with eating grass-fed steak and cutting out processed foods.
“When you eat fermented foods, it actually signals to the small intestine to produce endogenous GLP-1, which means it creates the natural form of Ozempic,” O’Mara says. “It’s a shortcut, or an improved way, of getting the benefits of Ozempic without having to get an expensive drug, and without the side effects.” That’s a big claim that needs to be studied further, but the research is promising. A 2025 review published in the Journal of Food Science found that fermented foods could potentially serve as a powerful tool for combatting obesity, by way of regulating appetite, insulin and the formation of new fat cells.
How much fermented food should you eat—and do probiotics count?
O’Mara encourages his clients to eat fermented foods with every meal. “Generally, it is dose dependent,” he says. “So, the more you do, the better,” although he acknowledges that at a certain level, the benefits likely top out. More important than obsessing over a specific quantity, he says, is to aim for variety. “You don’t want to just have one particular type of fermented food—the same brand, the same jar—every time,” he says. “You want to eat a huge variety of these fermented foods.”
Consistency seems to be important as well. “In the Stanford study, the gains in diversity and the drop in inflammation built up gradually over weeks of daily intake,” according to Johnson, who says he eats one-to-four tablespoons of fermented vegetables—mainly sauerkraut, kimchi, and fermented beets—daily, without exception. “Those trials tested steady daily consumption rather than the occasional forkful, so I treat fermented foods as a daily habit, not a now-and-then garnish.”
As for probiotics, these can be useful for filling gaps, just like vitamins, but shouldn’t be viewed as a stand-in for fermented foods, O’Mara says. "Probiotics are kind of a watered-down version of fermented foods,” he says. “They have benefits, and they still have a place, but fermented foods represent a richer and more varied source of bacteria.” There are also inherent benefits to choosing whole foods over anything that comes in capsule form. “When you eat fermented whole foods, you’re not only reaping the benefits of the fermentation but also all the nutrients that come with those foods,” says Tung. “When you eat kimchi, you’re also getting fiber and all the nutrients that come with eating vegetables. With yogurt, besides getting the benefits of the live cultures and probiotics, you’re also getting protein, calcium, and other minerals that are important for your health.”
Basically, eat fermented foods as often as you can, and add a probiotic to your supplement stack for good measure. And if you find yourself trying to cram a Ziploc full of kimchi into your spouse's bag, you’ve probably gone too far.