We cannot write-off pasteurized ferments as the dead, less healthy cousin to its unpasteurized, live relative. All fermented foods provide health benefits, pasteurized or not. We also need to avoid getting caught up in superfluous health claims around fermentation’s benefits. Instead, we should focus on including fermentation as part of a regular diet.
David Zilber explored how the microbial transformation of food intersects with our gut microbes during Stanford University’s Center for Human Microbiome Studies Fermentation & Health Speaker Series. With growing scientific interest in fermentation – and increasing interest from consumers – the health benefits become cloudy in marketing claims.
“If you eat regularly foods full of life, life that lives regularly in the foods you consume but also inside of you, then you can be said to be a ranger taking care of a healthy forest,” Zilber said. “The health benefits of fermented foods should equally be viewed as being meaningful when they turn into a regimen, like exercise.”
Health Claims
A 2021 study by Stanford researchers published in the journal Cell found regularly eating fermented foods boost microbiome diversity, improves immune response and decreases inflammation. But marketing of fermented products is often shrouded in hearsay.
“As far as health claims go…(there are) sometimes outlandish claims made by Westerners about cure-all superfoods that disproportionately, and I quote from one study I found, ‘Seemed to benefit the individuals that sell them the most,’” Zilber said.
Take kombucha, for example. He rattled off a list of health problems kombucha founders have claimed the fermented tea has cured, from AIDS to cancer to constipation.
“The problem is that all these claims seem to come, in one form or another, from anecdotes of people who drink kombucha and have lived a life,” he added. They’re not researched in reputable cohort studies. “This is why it’s sometimes hard to separate the wheat from the chaff when it comes to fermentation. The people who want to believe the benefits only decry its Praises when a positive correlation is made but they also tend to speak the loudest.”
Zilber pointed out that consuming fermented foods, whether or not it’s a product with proven health benefits, is certainly still beneficial. Eating fermented foods regularly means “you’re also omitting a whole slew of other foods” prevalent in a Western diet, like highly-processed and chemically-preserved foods.
“If you put kimchi on your plate at dinner, you leave off mashed potatoes. If you use water kefir as your drink with it, you aren’t drinking Coke,” he said. “And that’s an important link we also can’t forget, when it comes to thinking about the health benefits of fermented foods, they are in many means inherently healthy.”
Many cultures have fermented for thousands of years to preserve food. In Tibet, yak herders rely on cultural wisdom passed down from generations to ferment yak’s milk for milk and butter.
“We’ve evolved alongside our microbes both evolutionarily and culturally,” Zilber added. “To Tibetans their folk knowledge of what leads them to Long lives and health is intrinsically tied to the practices of preservation that have allowed them to thrive in some of the most rarified air on Earth.”
Pasteurized vs. Unpasteurized
What about purchasing pasteurized vs. unpasteurized ferments? Unpasteurized ferments include live microbes, but that doesn’t mean pasteurized ferments aren’t healthy.
“Sometimes in cooking, if you’re looking to achieve a great flavor, sometimes you have to kill microbes because you have to pasteurize them for whatever number of reasons,” Zilber added. But it doesn’t mean that the food is somehow not worth eating, it just means that it’s not live, but it still contains lots of benefits. … There is a benefit to consuming something that microbes have lived through, even if it’s not pasteurized.”
Elisa Caffrey, the speaker series host and a Stanford PhD candidate, agrees. The benefits of unpasteurized ferments have not been studied. During fermentation, Caffrey notes, the microbes are producing metabolites still present during pasteurization. A complete study would characterize the metabolites over the course of the fermentation process, identify chemical compounds and then analyze the compounds for their benefits.
“That landscape we don’t understand at all and it’s a very, very interesting world to start exploring,” she said. “Until we start understanding all the different components of these foods and the way that they interact with not only the microbes in fermented foods with each other but also with the body, it’s really hard to then make these very generalized health claims.”
Caffrey, Zilber and Justin Sonnenburg, PhD, professor of microbiology and immunology at Stanford, host the Fermentation & Health Speaker Series. The series will explore the topic over the next few months with different speakers ranging from a scientist, food researcher and pickle producer. Registration is free.