Nutrition professionals need to share the details when recommending fermented products to clients. What are the health benefits of the specific food or beverage ? Does the product contain probiotics? Live microbes?
“There are a vast array of fermented foods. This is important because it means there can be tasty, culturally appropriate options for everyone,” says Hannah Holscher, PhD and registered dietitian (RD). But, she adds, remember that these are complex products.
Holscher spoke at a webinar produced by the International Scientific Association for Probiotics and Prebiotics (ISAPP) and Today’s Dietitian. Joined by Jennifer Burton, RD and licensed dietitian/nutritionist (LDN), the two addressed the topic Fermented Foods and Health — Does Today’s Science Support Yesterday’s Tradition? Hosted by Mary Ellen Sanders, executive director of ISAPP, the presentation touched on the foundational elements of fermented foods, their differences from probiotics, the role of microbes in fermentation, current scientific evidence supporting health claims and how to help clients incorporate fermented foods in their diets.
Sanders called fermented foods “one of today’s hottest food categories.” Today’s Dietitian surveys show they are a top interest to dietitians, as the general public often turns to them with questions about fermented foods and digestive health.
Here are three factors highlighted in the webinar that dietitians should consider before recommending fermented foods and beverages.
Does It Contain Live Microbes?
Fermentation is a metabolic process – microorganisms convert food components into other substances.
In the past decade, scientists have applied genomic sequencing to the microbial communities in fermented foods. They’ve found there’s not just one microbe involved in fermentation, Holscher explained, there may be many. The most common microbes in fermented foods are streptococcus, lactobacillaceae, lactococcus and saccharomyces.
But deciphering which fermented food or beverages contains live microbes can be difficult.
Live microorganisms are present in foods like yogurt, miso, fermented vegetables and many kombuchas. But they are absent in foods that were fermented then heat-treated through baking and pasteurization (like bread, soy sauce, most vinegars and some kombucha). They’re also absent in fermented products that are filtered (most wine and beers) or roasted (coffee and cacao). And there are foods that are mistakenly considered fermented but are not, like chemically-leavened bread, vegetables pickled in vinegar and non-fermented cured meats and fish.
“The main take-home message is that it’s not always easy to tell if a food is a fermented food or not. So you may need to do more digging, either by reading the label more carefully or potentially contacting the food manufacturer,” Holscher said. “When we just think of if live microbes are present or not, a good rule of thumb is if that food is on the shelf at your grocery store, it’s very likely that it does not contain live microbes.”
Does It Contain Probiotics?
The dietitians stressed: probiotics are not the same as fermented foods.
“Probiotics are researched as to the strains and the dosages to be able to connect consumption of a probiotic to a health outcome,” Holscher said. “These strains are taxonomically defined, they’ve been sequenced, we know what these microorganisms can do. They also have to be provided in doses of adequate amounts of the live microbes so foods and supplements are sources of probiotics.”
Though fermented foods can be a source of probiotics, Holscher notes: “In most fermented foods, we don’t know the strain level designation.”
“For most of the microbes in fermented foods, we’ve just really been doing the genomic sequencing of those over the last 10 years and so we may only know them to the genus level right,” she said. For example, we know lactic acid bacteria are present in kimchi and sauerkraut.
Holscher suggests, if a client has a specific health need, a probiotic strain should be recommended based on its evidence-based benefits. For example, the probiotic strain saccharomyces boulardii is known to help prevent travel-related diarrhea, and so would be good for a patient to take before a trip.
“If you’re looking to support health and just in general, fermented foods are a great way to go,” Holscher says.
The speakers recommended looking for probiotic foods in the Functional Food Section of the U.S. Probiotic Guide.
Does Research Support Health Claims?
Fermentation contributes to the functional and nutritional characteristics of foods and beverages. Fermented foods can: inhibit pathogens and food spoilage microbes, improve digestibility, increase vitamins and bioactives in food, remove or reduce toxic substances or anti-nutrients in food and have health benefits.
But research into fermented foods has been minimal, mostly limited to fermented dairy. Dietitians should be careful making strong recommendations based on health claims unless those claims are supported by research. And food labels should always be scrutinized.
“There’s a lot of voices out there that are trying to answer this question [Are fermented foods good for us?],” says Burton. “Many food manufacturers have published health claims on their labels talking about these benefits and, while those claims are regulated, they’re not always enforced. Just because it has a food health claim on it, that claim may not be evidence-based. There’s a lot of anecdotal accounts of benefits coming from eating fermented foods and the research is suggesting some exciting potential mechanisms. But overall we know as dietitians we have an ethical responsibility to practice on the basis of sound evidence and to not make strong recommendations if those are not yet supported by research.”
Reputable health claims are documented in randomized control trials. But only “possible benefits” can be linked to nonrandomized controlled trials. And non-controlled trials are the least conclusive studies of all.
For example, Burton puts miso in the “possible benefits” category because, with its high sodium content, there’s not enough research indicating it’s safe for patients with heart disease. Similarly, she does not recommend kombucha because of its extremely limited clinical research and evidence.
“We have to use caution in making these recommendations,” Burton says.
This is why Burton advises dietitians to be as specific as possible. Don’t just tell patients “eat fermented foods” — list the type of fermented food and its brand name. She also says to give patients the “why” — what is the benefit of this fermented food? Does it increase fiber or boost bioavailability of nutrients?
“Are fermented foods good for us? It’s safe to say yes,” Burton says. “There’s a lot that we don’t know, but the body of evidence suggests that fermentation can improve the beneficial properties of a food.”
A new study found fermented dairy products reduce memory loss. The study, published in Nutritional Neurosciences, confirms there is a connection between the gut microbiome and the nervous system, known as the gut-brain axis
The adults in the test regularly consumed a dairy-based fermented drink, containing 25-30 billion colony forming units (CFUs). Drinking fermented dairy — like yogurt, kefir or fermented whey — “increased the presence of certain microorganisms in the gut and improved relational memory in healthy adults.”
Read more (Nutritional Neurosciences)
Can indigenous fermented beverages play a prominent role in a healthy diet? Biochemists studied four commercial products – kefir and ryazhenka from Russia, amasi and mahewu from South Africa. Their research was published in the journal Foods.
Researchers from the Institute of the Research Center of Biotechnology of the Russian Academy of Science (RAS) and South Africa’s Durban University of Technology discovered key elements of the fermented drinks. The three that are milk-based had more antioxidants than the corn-based one, while the corn drink (mahewu) was “better at suppressing the angiotensin-converting enzyme.” Kefir and ryazhenka, meanwhile, have a more diverse composition of fatty acids.
“Usually, food is considered only as a source for sustenance. However, more and more people (are starting) to believe that it also should preserve and improve health,” Konstantin Moiseenko, co-author of the study and a research fellow at RAS in Moscow. He notes modern science allows “mankind to look differently at the usefulness of traditional, centuries-old foods. Our research focuses on fermented products, which regular consumption can potentially prevent atherosclerosis, hypertension and thrombosis.”
We’re on the cusp of a new generation of health-promoting foods, foods that will harness the power of microbes present in fermented foods and beverages.
Paul Cotter, head of Food Bioscience Department at Teagasc Food Research Centre in Ireland, envisions a future system where fermented foods are made with strains having scientifically-proven health-promoting benefits. His lab is integrating microbiome and metabolic data and using DNA sequencing to drill down to specific health benefits.
“We’ve really only scratched the surface as to the real potential of all those different microbes and what they could be doing,” says Cotter, who is also the principal investigator with the APC Microbiome Ireland. “Whether a particular food is health promoting or not will be dictated by what microbe is in there and can only be proved by carrying out the appropriate studies.”
Cotter was a speaker at TFA’s conference FERMENTATION 2021. He made a case for establishing minimum standards for fermented foods and beverages. In his scenario, kombucha or kefir couldn’t be labeled as such without using a scientifically-backed combination of microbial strains.
“That ensures that the kind of pseudo fermented foods — the foods that are fermented but not really with the right microbes — don’t get on the market or can’t be distinguished,” Cotter says.
Not all Fermented Foods are Equal
There is scientific evidence of the health benefits of frequently and regularly consuming fermented foods and beverages. They can prevent illness, provide a source of live and active microbes, improve the digestibility of foods, increase certain vitamins and bioactive compounds and remove or reduce toxic compounds like lactose.
“Ultimately, I’m a scientist and so I want to see proof that underpins the claims associated with a particular food,” Cotter says. “While there’s a lot of good information out there, I think also some of the claims are doing a disservice to the fermented food industry and to those who make fermented foods in their homes because they’re overstating the potential health benefits.”
Problematic, too, are fermented foods made with shortcuts and additives. Cotter’s lab is currently studying kefir, and they found that not all are equal. Traditional kefir has been documented as helping to reduce weight and improve cholesterol and liver triglyceride levels. But some brands of commercial kefir they studied didn’t produce those same health benefits. And they found that some of the kefir on the market was nothing more than watered-down yogurt.
“Consumer beware: the benefits weren’t the same for each kefir and differ depending on what the microbes present in the kefir were,” says Cotter, a self-described fermented foods nerd. ”I think that’s a problem for lots of other fermented foods too, and I really feel for consumers who don’t have a microbiological background and are reading a label and assuming that they are consuming a fermented beverage or fermented food that has lots of beneficial microbes in there and is made in the artisanal way that that food has been made over hundreds of different years.”
What are the health benefits?
Cotter’s lab has used in-depth analyses to detail the microbial composition of a food, including naming the microorganisms present and their capabilities. They’ve identified “completely novel species that had never been found previously,” Cotter says. An example is African fermented food, which contains a huge diversity of microbes, including ones not typically found in fermented foods in the West.
The highest level of what’s called “Health Associated Gene Clusters” are in fermented foods, specifically those brine- (like sauerkraut and kimchi) or sugar-based (kefir and kombucha). Cotter notes the genes in fermented foods are health promoting because the microbes are closely related to probiotics.
“What we can do is to try to harness the microbes that are present and use them in a way that facilitates large-scale production,” Cotter says.
Renowned professor, epidemiologist and author of The Diet Myth and Spoon Fed Tim Spector is encouraging people to eat the 4k’s: kefir, kombucha, kimchi and kraut. His studies found diet plays a role in preventing severe symptoms of Covid.
Spector is a leading expert on long Covid, the symptoms that can continue for extended periods after an initial infection. He leads the ZOE Covid Study, created by scientists and doctors at King’s College London (where he is based), Stanford, Harvard, Massachusetts General Hospital and health science company ZOE. Last year Spector helped research the attributes and predictors of long Covid, the results of which were published in the journal Nature Medicine.
A microbiome researcher, Spector advocates for people to eat a diverse diet to improve the trillions of microbes in the gut.
“We know from Covid now that your gut health is crucial for your immune system,” he told ITV. “If we can focus on our gut health…gut microbiome is really crucial.”
Diet must be high-quality to improve immunity, he stresses. In the ZOE Covid study, researchers have found eating “the right things and avoiding feeding (the gut) the bad things, that’s what made the difference to getting long Covid,” he said. Fermented foods have proven health benefits, but Spector says many people opt for cheaply-made yogurts and cheeses prevalent in the grocery store to get their daily dose of fermented foods. This dairy is full of sugar and artificial ingredients, which thwart the positive effects of fermentation.
“The other fermented foods that many people don’t know about are what I call the 4 k’s,” Spector says: kefir, kombucha, kimchi and kraut (sauerkraut). He encourages “small shots a day” of a fermented food or beverage. “That really is a powerful enhancer of your microbes. And all these things are going to be cheaper actually than taking multivitamins every day of your life.”
Spector is not a fan of supplements, like pill forms of vitamins and nutrients. Many are proven not to work, he explained. In his studies on the effects of supplements on long Covid, there were minimal benefits for women and none for men.
“People are much better off getting all their vitamins and nutrients by having a diverse diet,” Spector said.
Microbes on our bodies outnumber our human cells. Can we improve our health using microbes?
“(Humans) are minuscule compared to the genetic content of our microbiomes,” says Maria Marco, PhD, professor of food science at the University of California, Davis (and a TFA Advisory Board Member). “We now have a much better handle that microbes are good for us.”
Marco was a featured speaker at an Institute for the Advancement of Food and Nutrition Sciences (IAFNS) webinar, “What’s What?! Probiotics, Postbiotics, Prebiotics, Synbiotics and Fermented Foods.” Also speaking was Karen Scott, PhD, professor at University of Aberdeen, Scotland, and co-director of the university’s Centre for Bacteria in Health and Disease.
While probiotic-containing foods and supplements have been around for decades – or, in the case of fermented foods, tens of thousands of years – they have become more common recently . But “as the terms relevant to this space proliferate, so does confusion,” states IAFNS.
Using definitions created by the International Scientific Association for Postbiotics and Prebiotics (ISAPP), Marco and Scott presented the attributes of fermented foods, probiotics, prebiotics, synbiotics and postbiotics.
The majority of microbes in the human body are in the digestive tract, Marco notes: “We have frankly very few ways we can direct them towards what we need for sustaining our health and well being.” Humans can’t control age or genetics and have little impact over environmental factors.
What we can control, though, are the kinds of foods, beverages and supplements we consume.
It’s estimated that one third of the human diet globally is made up of fermented foods. But this is a diverse category that shares one common element: “Fermented foods are made by microbes,” Marco adds. “You can’t have a fermented food without a microbe.”
This distinction separates true fermented foods from those that look fermented but don’t have microbes involved. Quick pickles or cucumbers soaked in a vinegar brine, for example, are not fermented. And there are fermented foods that originally contained live microbes, but where those microbes are killed during production — in sourdough bread, shelf-stable pickles and veggies, sausage, soy sauce, vinegar, wine, most beers, coffee and chocolate. Fermented foods that contain live, viable microbes include yogurt, kefir, most cheeses, natto, tempeh, kimchi, dry fermented sausages, most kombuchas and some beers.
“There’s confusion among scientists and the public about what is a fermented food,” Marco says.
Fermented foods provide health benefits by transforming food ingredients, synthesizing nutrients and providing live microbes.There is some evidence they aid digestive health (kefir, sourdough), improve mood and behavior (wine, beer, coffee), reduce inflammatory bowel syndrome (sauerkraut, sourdough), aid weight loss and fight obesity (yogurt, kimchi), and enhance immunity (kimchi, yogurt), bone health (yogurt, kefir, natto) and the cardiovascular system (yogurt, cheese, coffee, wine, beer, vinegar). But there are only a few studies on humans that have examined these topics. More studies of fermented foods are needed to document and prove these benefits.
Probiotics, on the other hand, have clinical evidence documenting their health benefits. “We know probiotics improve human health,” Marco says.
The concept of probiotics dates back to the early 20th century, but the word “probiotic” has now become a household term. Most scientific studies involving probiotics look at their benefit to the digestive tract, but new research is examining their impact on the respiratory system and in aiding vaginal health.
Probiotics are different from fermented foods because they are defined at the strain level and their genomic sequence is known, Marco adds. Probiotics should be alive at the time of consumption in order to provide a health benefit.
Postbiotics are dead microorganisms. It is a relatively new term — also referred to as parabiotics, non-viable probiotics, heat-killed probiotics and tyndallized probiotics — and there’s emerging research around the health benefits of consuming these inanimate cells.
“I think we’ll be seeing a lot more attention to this concept as we begin to understand how probiotics work and gut microbiomes work and the specific compounds needed to modulate our health,” according to Marco.
Prebiotics are, according to ISAPP, “A substrate selectively utilized by host microorganisms conferring a health benefit on the host.”
“It basically means a food source for microorganisms that live in or on a source,” Scott says. “But any candidate for a prebiotic must confer a health benefit.”
Prebiotics are not processed in the small intestine. They reach the large intestine undigested, where they serve as nutrients for beneficial microorganisms in our gut microbiome.
Synbiotics are mixtures of probiotics and prebiotics and stimulate a host’s resident bacteria. They are composed of live microorganisms and substrates that demonstrate a health benefit when combined.
Scott notes that, in human trials with probiotics, none of the currently recognized probiotic species (like lactobacilli and bifidobacteria) appear in fecal samples existing probiotics.
“There must be something missing in what we’re doing in this field,” she says. “We need new probiotics. I’m not saying existing probiotics don’t work or we shouldn’t use them. But I think that now that we have the potential to develop new probiotics, they might be even better than what we have now.”
She sees great potential in this new class of -biotics.
Both Scott and Marco encouraged nutritionists to work with clients on first improving their diets before adding supplements. The -biotics stimulate what’s in the gut, so a diverse diet is the best starting point.
Scott Whitley, of failed LAB Water Kefir, shares lessons learned from launching – and then shuttering — the business. Whitley is open about his blunders, providing great insights for fermentation brands.
His first problem: Knowing nothing about the food and beverage industry, and even less about selling a fermented drink. The company used a recipe that contained fermentation blunders, so products exploded on store shelves!
Second problem: Spending too much time on low-leverage activities. The two co-founders were filling tens of thousands of bottles of water kefir themselves — something Whitley says in hindsight “was a big mistake.” They thought they were saving money but, in reality, they weren’t making enough money to stay afloat. Bottles sold for $5.50 at retail, and stores bought them for $3.30. After covering production costs, LAB Water Kefir made only $1.10 per bottle. They were bringing in a few thousand dollars per month, but expenses were over $6,500.
Third problem: Lack of consumer understanding. The brand sold well at farmers markets, where half the people who approached their stand and sampled the drink would buy a bottle. But they learned that many people didn’t know what water kefir was. Whitley shares the story of watching a man grab a bottle off the shelf, shake it, then open it to drink – and the water kefir shot out of the bottle and all over his face. Also, people don’t go to a grocery store to experiment with a new, pricey drink, so their water kefir didn’t sell well at retail.
Read more about the story behind the brand at Trends.
Read more (Trends)
After a study found 91% of plant-based, fermented drinks in Ireland make unauthorized health claims, the Food Safety Authority of Ireland (FSAI) has published a guide on how to produce such beverages safely and label them accurately.
The FSAI examined 32 unpasteurized drinks currently sold on the Irish market – including kombucha, kefir and ginger soda – and found that most did not comply with EU and Irish food labelling and health regulations. The study found 13% had alcohol levels above labelling thresholds, and 75% lacked required label information, like the address of the producer and “best-before” date.
“The methods used in producing unpasteurized fermented plant-based products can be difficult to manage,” notes Dr. Pamela Byrne, FSAI chief executive. “The guidance will help producers to achieve consistent production methods, safe storage, safe handling and safe transportation of fermented beverages.”
Read more (Agriland)
A diet high in fermented foods increases microbiome diversity, lowers inflammation, and improves immune response, according to researchers at Stanford University’s School of Medicine.The groundbreaking results were published in the journal Cell.
In the clinical trial, healthy individuals were fed for 10 weeks, a diet either high in fermented foods and beverages or high in fiber. The fermented diet — which included yogurt, kefir, cottage cheese, kimchi, kombucha, fermented veggies and fermented veggie broth — led to an increase in overall microbial diversity, with stronger effects from larger servings.
“This is a stunning finding,” says Justin Sonnenburg, PhD, an associate professor of microbiology and immunology at Stanford. “It provides one of the first examples of how a simple change in diet can reproducibly remodel the microbiota across a cohort of healthy adults.”
Researchers were particularly pleased to see participants in the fermented foods diet showed less activation in four types of immune cells. There was a decrease in the levels of 19 inflammatory proteins, including interleukin 6, which is linked to rheumatoid arthritis, Type 2 diabetes and chronic stress.
“Microbiota-targeted diets can change immune status, providing a promising avenue for decreasing inflammation in healthy adults,” says Christopher Gardner, PhD, the Rehnborg Farquhar Professor and director of nutrition studies at the Stanford Prevention Research Center. “This finding was consistent across all participants in the study who were assigned to the higher fermented food group.”
Microbiota Stability vs. Diversity
Continues a press release from Stanford Medicine News Center: By contrast, none of the 19 inflammatory proteins decreased in participants assigned to a high-fiber diet rich in legumes, seeds, whole grains, nuts, vegetables and fruits. On average, the diversity of their gut microbes also remained stable.
“We expected high fiber to have a more universally beneficial effect and increase microbiota diversity,” said Erica Sonnenburg, PhD, a senior research scientist at Stanford in basic life sciences, microbiology and immunology. “The data suggest that increased fiber intake alone over a short time period is insufficient to increase microbiota diversity.”
Justin and Erica Sonnenburg and Christopher Gardner are co-authors of the study. The lead authors are Hannah Wastyk, a PhD student in bioengineering, and former postdoctoral scholar Gabriela Fragiadakis, PhD, now an assistant professor of medicine at UC-San Francisco.
A wide body of evidence has demonstrated that diet shapes the gut microbiome which, in turn, can affect the immune system and overall health. According to Gardner, low microbiome diversity has been linked to obesity and diabetes.
“We wanted to conduct a proof-of-concept study that could test whether microbiota-targeted food could be an avenue for combatting the overwhelming rise in chronic inflammatory diseases,” Gardner said.
The researchers focused on fiber and fermented foods due to previous reports of their potential health benefits. High-fiber diets have been associated with lower rates of mortality. Fermented foods are thought to help with weight maintenance and may decrease the risk of diabetes, cancer and cardiovascular disease.
The researchers analyzed blood and stool samples collected during a three-week pre-trial period, the 10 weeks of the diet, and a four-week period after the diet when the participants ate as they chose.
The findings paint a nuanced picture of the influence of diet on gut microbes and immune status. Those who increased their consumption of fermented foods showed effects consistent with prior research showing that short-term changes in diet can rapidly alter the gut microbiome. The limited changes in the microbiome for the high-fiber group dovetailed with previous reports of the resilience of the human microbiome over short time periods.
Designing a suite of dietary and microbial strategies
The results also showed that greater fiber intake led to more carbohydrates in stool samples, pointing to incomplete fiber degradation by gut microbes. These findings are consistent with research suggesting that the microbiome of a person living in the industrialized world is depleted of fiber-degrading microbes.
“It is possible that a longer intervention would have allowed for the microbiota to adequately adapt to the increase in fiber consumption,” Erica Sonnenburg said. “Alternatively, the deliberate introduction of fiber-consuming microbes may be required to increase the microbiota’s capacity to break down the carbohydrates.”
In addition to exploring these possibilities, the researchers plan to conduct studies in mice to investigate the molecular mechanisms by which diets alter the microbiome and reduce inflammatory proteins. They also aim to test whether high-fiber and fermented foods synergize to influence the microbiome and immune system of humans. Another goal is to examine whether the consumption of fermented foods decreases inflammation or improves other health markers in patients with immunological and metabolic diseases, in pregnant women, or in older individuals.
“There are many more ways to target the microbiome with food and supplements, and we hope to continue to investigate how different diets, probiotics and prebiotics impact the microbiome and health in different groups,” Justin Sonnenburg said.
Other Stanford co-authors are Dalia Perelman, health educator; former graduate students Dylan Dahan, PhD, and Carlos Gonzalez, PhD; graduate student Bryan Merrill; former research assistant Madeline Topf; postdoctoral scholars William Van Treuren, PhD, and Shuo Han, PhD; Jennifer Robinson, PhD, administrative director of the Community Health and Prevention Research Master’s Program and program manager of the Nutrition Studies Group; and Joshua Elias, PhD.
The kefir brands recently tested for their probiotic claims are challenging the results.
In May, a study found 66% of commercial kefir products overstated probiotic counts and “contained species not included on the label.” The Journal of Dairy Science Communications published the peer-reviewed work by researchers at the University of Illinois and Ohio State University.
“Based on the results…there should be more regulatory oversight on label accuracy for commercial kefir products to reduce the number of claims that can be misleading to consumers,” reads the study. “Classification as a ‘cultured milk product’ by the FDA requires disclosure of added microorganisms, yet regulation of ingredient quality and viability need to be better scrutinized. All 5 kefir products guaranteed specific bacterial species used in fermentation, yet no product matched its labeling completely.”
Researchers tested two bottles of each of five major kefir brands: Maple Hill Plain Kefir, Siggi’s Plain Filmjölk, Redwood Hill Farm Plain Goat Milk Kefir, CoYo Kefir and Lifeway Original Kefir. Bottles were measured for microbial count and taxonomy to validate label claims.
The Fermentation Association reached out to the five brands involved and asked for their responses to the results. Redwood Hill and Lifeway both submitted detailed statements. Maple Hill, Siggi’s and CoYo did not return multiple requests for comment.
Probiotics in fermented products are listed in colony-forming units (CFUs), and the study found kefir from both Lifeway and Redwood Hill contained fewer CFUs than what was claimed on the label. But these brands — who send their products to third-party labs for testing — said the results are not accurate.
Lifeway refutes the assertion that their Original Kefir did not meet the claimed probiotic count. Lifeway references U.S. Food and Drug Administration food labeling laws, which dictate that a product “must provide all nutrient and food component quantities in relation to a serving size.” Lifeway’s label on their 32-ounce bottle says that the serving size of kefir is 1 cup, making the claim of 25-30 billion CFUs per serving size accurate.
The study results, Lifeway notes in their statement, were “premised upon an erroneous assumption that Lifeway claims it has 25-30 billion CFUs per gram” rather than per serving size.
“The authors’ flawed assumption is perhaps a result of their lack of familiarity with FDA labeling requirements or a result of merely overlooking the details in order to support their intended conclusions going into the testing,” reads a statement from Lifeway.
In fact, Lifeway points out, the study’s “erroneous conclusion premised upon the flawed assumption…actually proves the accuracy of Lifeway’s claim of 25-30 billion CFUs per (8 ounce) serving.”
Redwood Hill Farm, too, refutes the study’s conclusion. Their Goat Milk Kefir currently includes the phrase “millions of probiotics per sip” on its label. The label referenced in the study was an old version that claimed “hundreds of billions” of probiotics, which was discontinued last year. According to Redwood Hill Farm, that old label was based on third-party testing that confirmed hundreds of billions of CFUs per 8-ounce serving. But careful review of the kefir’s probiotic counts in 2019-2020 found some CFUs in the hundreds of billions and others in the tens of billions. Redwood Hill changed their label to millions rather than billions “to be absolutely sure that we could meet our target claim on a consistent basis.”
Variation in CFU counts is common in traditional plating testing techniques. Redwood Hill referenced a study published in Nutritional Outlook that found that plating results can vary 30-50%.
“Given the challenges around probiotic CFU enumeration, we were not too surprised to see a discrepancy between the number of CFUs in our Goat Milk Kefir found in the study and our past analyses,” reads the statement from Redwood Hill Farm. “Like all living organisms, probiotics are challenging to control and measure. A particular microorganism’s ability to reproduce is impacted by a variety of factors, including temperature, oxygen level, variations in the nutrient composition of the milk, and pH level. Our kefir has a sixty-day shelf life and during that time the different types of bacteria in the product will peak and die-off in relation to the conditions those particular bacteria like. For example, fermented dairy products naturally become more acidic (lower pH) as they age and while some bacteria thrive in acidic environments, others’ reproduction is stunted. This makes the exact CFU count rather volatile not only from bottle to bottle, but also throughout the timespan between when that bottle leaves our facility and when it expires.”
Redwood Hill Farm’s most recent testing measured 400 million CFUs per gram or 96 billion per serving (1 cup). These figures compare with what the study found — 193 million CFUs per gram or 46 billion per serving.
“Although the University of Illinois study found only half the probiotic cells that our study did, this is actually not that wide of a variation in bacteria reproduction based on all of the conditional factors outlined above,” their statement reads.
The study’s test results found all kefir brands contained species not on the label. Lifeway notes their culture claims are based on the time of manufacture, not on expiration date. “Moreover, the authors validate that all of the claimed culture species except for the bifidos, Leuconostoc and L. reuteri, (which could be at a low concentration due to time of shelf-life), were identified in their testing,” reads Lifeway’s statement.
Redwood Hill Farm says that, based on the study results (that “2 Lactobacillus delbrueckii subspecies or 3 Lc. lactis subspecies could not be identified” in their kefir), they are pursuing further analysis. They’ve contacted their culture supplier for further insight, and are sending new samples to a third-party lab.
“These cultures are at the heart of the product and are what transforms the goat milk into a yogurt drink with its characteristic thick and creamy texture and tart flavor,” reads the Redwood Hill Farm statement. “It’s difficult to understand how these core active agents in the kefir could not be present in the product at any stage in its lifecycle.”
DNA vs. Plating Methodology
The study utilized both DNA sequencing and traditional plating methodologies, even though plating testing alone is considered the industry standard for kefir. Plating testing for kefir is done in a microbiology laboratory where it’s incubated to determine bacteria colony growth.
The study itself notes: “Limitation of DNA-based sequencing methods could explain why taxa stated on labels were not detected and why unclaimed viable species were identified.”
Lifeway points out: “This concession as to testing limitations is critical to note as it is but one explanation of many as to why various species may have not been detected. First and foremost, the authors fail to validate the DNA extraction method to establish that it delivers all the available DNA in the type of dairy product analyzed; for example, they do not appear to have broken down the calcium bonds. Further, they appear to not have undertaken the required extra enzymatic treatments. Moreover, for their microanalysis, they are using MRS [a method for cultivation of lactobacilli] but only incubating for 48 hours. As most kefir products would contain a significant amount of Lactococci, there is a high chance of not detecting this species unless you go to 72 hours of incubation. Another unknown important factor in the testing is the time period within the cycle of the shelf-life of the product that was tested. This is critical as the longer the product sits on a shelf, the fewer number of live and active bacteria will be present.”
Meanwhile, Redwood Hill Farm says “our team will continue to educate ourselves on the application of DNA sequencing technology to fermented food product probiotic count analysis and what opportunities and limitations this methodology may offer versus traditional plating techniques.”