Fermented foods overhyped? Kefir study shows some labels exaggerate probiotic content

From pop culture to the wellness industry, gut health has been the topic of conversation and the latest product craze. Fermented foods like kefir, kombucha, and kimchi have flown off the shelves at much faster rates than previous years thanks to people looking to reap the numerous benefits of their “good bacteria.” 

Fermented foods and supplements have a positive impact on the gut, as well as moderating immune responses, heart health, weight, and even mood. Their popularity is warranted, but skeptics and scientists wonder—do the products live up to the bold claims made on their labels? 

Putting Foods to the Test

Researchers from the University of Illinois and Ohio State University put five brands of kefir, a fermented dairy beverage reminiscent of drinkable yogurt, to the test. Using two bottles of kefir from each of the five major brands, the team of researchers used DNA sequencing to identify bacterial species.

Their results indicated that most brands exaggerated the bacterial density of their fermented products and contained species not listed on the label. Only one of the five had the bacterial content it claimed at 10 billion bacteria per gram, while all others failed to meet the mark with 10 million in a product claiming 100 billion and one billion in a product claiming 10 billion. 

The bacterial strains the team identified were then compared to the strains listed on product labels, verifying multiple inconsistencies. While some strains listed on labels were entirely absent from product contents, others identified were unlisted yet present. 

Each of the five products analyzed contained bacterial species Streptococcus salivarius but did not list it, and all but one contained Lactobacillus paracasei. Both are fairly safe and very commonly used as starter strains in the production of yogurts and fermented foods. It is likely that the strains also add to the health benefits of the product, making it unclear why they are not included on the labels. 

“Our study shows better quality control of kefir products is required to demonstrate and understand their potential health benefits,” says Kelly Swanson, in a recent statement. Swanson is the Kraft Heinz Company Endowed Professor in Human Nutrition in the Department of Animal Sciences and the Division of Nutritional Sciences at Illinois. “It is important for consumers to know the accurate contents of the fermented foods they consume.” 

The labels of fermented products include a measure of the amount of colony-forming units per gram (cfu/g). A larger amount of bacteria per gram is considered more beneficial to the consumer’s gut health. Most companies promise their products to contain a minimum of a billion bacteria per gram, but others claim as much as 100 billion. However, these claims are lightly regulated at best, since the U.S. Food and Drug Association considers them “Generally Recognized as Safe.” Unfortunately, this leaves customers with little clarity on the true contents and benefits of the products they consume,” adds Swanson.

“Just like probiotics, the health benefits of kefir and other fermented foods will largely be dependent on the type and density of microorganisms present. With trillions of bacteria already inhabiting the gut, billions are usually necessary for health promotion. These product shortcomings in regard to bacterial counts will most certainly reduce their likelihood of providing benefits,” Swanson explains.

Significance of Accurate Labels

This study tested only five products, though Swanson stated he believes the results are representative of a problematic pattern in the fermented foods market. Labels are inaccurately representing the contents of their products, offering little transparency for customers looking to enjoy the promised benefits. 

“Even though fermented foods and beverages have been important components of the human food supply for thousands of years, few well-designed studies on their composition and health benefits have been conducted outside of yogurt,” Swanson adds. “Our results underscore just how important it is to study these products, and given the absence of regulatory scrutiny, consumers should be wary and demand better-quality commercial fermented foods.”

This study is published in JDS Communications

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