Kefir grains on a spoon. (© Ildi - stock.adobe.com)
URBANA, Ill. – Probiotics are big business these days, with more and more people focusing on maintaining a healthy gut. The benefits of “good bacteria” in fermented foods like kefir, kombucha, and kimchi don't just help the gut however, they also improve the immune system, heart health, and even your mental health. Unfortunately, a new study finds some of these products are not delivering all the benefits their labels claim.
Researchers from the University of Illinois and The Ohio State University say the bacterial content of several popular brands of kefir, a fermented dairy beverage, don't even come close to the levels their producers advertise. Moreover, study authors discovered bacterial species not included in the food labels at all.
“Our study shows better quality control of kefir products is required to demonstrate and understand their potential health benefits. It is important for consumers to know the accurate contents of the fermented foods they consume,” says U of I's Kelly Swanson, the Kraft Heinz Company Endowed Professor in Human Nutrition, in a university release.
Kefir labels making promises the products don't keep
For consumers buying a lot of gut-healthy groceries, they may be familiar with fermented products listing the “colony-forming units per gram” (cfu/g). Researchers explain that the more healthy bacteria per gram in a food, the more likely it will provide healthy boosts.
Most probiotic companies guarantee a minimum of one billion bacteria per gram in their products. However, some go as far as to claim their kefir has between 10 and 100 billion bacteria.
So you may be asking, why doesn't the federal government crack down on this? Study authors say since food-fermenting microorganisms have a long history of use, don't cause disease, and don't contain harmful ingredients, the U.S. Food and Drug Administration considers them “Generally Recognized As Safe” (GRAS). This means companies don't have to get extra approval for use and are generally free to make whatever claims they want about bacteria counts without government oversight.
Swanson's team purchased two bottles of five major kefir brands for testing. Researchers cultured and counted bacterial cells and also sequenced their DNA to reveal the different bacteria species in each brand.
Results reveal only one brand of kefir actually delivered on its promise of having 10 billion bacteria per gram. The other four fell dramatically short of their label's claims. One brand of kefir had only 10 million bacteria per gram, despite promising consumers 100 billion. Another only had one billion while its label advertised 10 billion.
“Just like probiotics, the health benefits of kefirs and other fermented foods will largely be dependent on the type and density of microorganisms present,” Swanson explains. “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.”
What bacteria are labels NOT telling you about
Along with inaccurate bacteria counts, the study reveals “distinct discrepancies” in what bacteria is actually in these bottles. Some of the species identified by the DNA tests did not appear on the labels altogether.
Study authors report all five brands contained, but did not list, Streptococcus salivarius. Four also contained Lactobacillus paracasei. Both of these are common starter strains of bacteria used in the production of yogurts or other fermented products. They're also generally safe for use and Swanson says it's not clear why companies would not list them.
While the study only examines five popular kefir brand, researchers conclude it's likely this problem is currently affecting the entire fermented foods market.
“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. Our results underscore just how important it is to study these products,” Swanson says. “And given the absence of regulatory scrutiny, consumers should be wary and demand better-quality commercial fermented foods.”
The study appears in the journal JDS Communications.
