Feeding kefir to mice has modulated their behavior via the gut-brain-axis (GBA), according to a new APC Microbiome Ireland study. Its findings show that two varieties of kefir, Fr1 and UK4, had different and positive effects on the immune system and various behaviors of the mice. As kefir demand continues to rise in the gut health space, this research supports the recent broadening of the definition of psychobiotics to include fermented foods and could optimize future generations of kefir products.
“On one level, it may seem very surprising that food that targets the gut microbes could modulate behavior. However, there is increasing evidence in basic and even human research showing the importance of gut microbes for brain health. Based on these results, we can begin to identify the key strains and mechanisms of action involved to harness them more specifically,” co-author Dr. John Cryan, Principal Investigator at APC Microbiome Ireland, tells.
“The results highlight yet further potential benefits of consuming kefir and are among the first to clearly show effects on behavior,” he explains. “Moreover, specific kefirs have already been shown to confer different health benefits and the microorganisms contained with kefir and lactic acid bacteria (LAB) in particular, are closely related to probiotic strains that have previously been shown to influence the GBA.”
Personalized nutrition and GBA spotlighted
Published in the Microbiome Journal, the study divided the mice into four groups of 12 – two groups gavaged with Fr1 and UK4, respectively, one cow’s milk control group and an untreated group. For three weeks, the treated mice were administered kefir or milk once daily. The results showed that Fr1 ameliorated the stress-induced decrease in serotonergic signaling in the colon and reward-seeking behavior in the saccharin preference test. Fr1 also ameliorated the milk gavage stress-induced elevation in neutrophil levels and CXCL1 levels.
UK4 kefir, on the other hand, increased fear-dependent contextual memory, yet decreased milk gavage-induced improvements in long-term spatial learning. It also reduced repetitive behavior and ameliorated stress-induced deficits in reward-seeking behavior.
The researchers found that both kefirs significantly changed the composition and functional capacity of the mice’s microbiota, where specific bacterial species were changed in a kefir-dependent manner. Both kefirs increased the capacity of the gut microbiota to produce Gamma aminobutyric acid (GABA). They also increased the prevalence of L. reuteri, E. plexicaudatum, and B. pseudolongum. Notably, L. reuteri is a bacterial strain known for its numerous beneficial effects on host immunity and metabolism.
This touches upon a central point that APC Microbiome Ireland has been advocating for years. “Health benefits depend on the microbial strain(s) consumed. We suspect that the results will make kefir an even more attractive product for the nutrition industry and consumers, but the key will be to produce and consume kefir that contains the correct strains for a particular individual’s needs – translating into personalized nutrition,” says Dr. Cryan.
Meanwhile, DuPont Nutrition & Biosciences embarked on a four-year project with the APC Microbiome Ireland SFI Research Centre to rebalance the gut bacteria of babies after antibiotics or Caesarean-section births. The focus is currently on probiotics and microbiome therapeutics, but it could also expand to food ingredients and symbiotics, the research institute highlights.
Kefir on the rise
Dr. Cryan underscores how kefir has become considerably more popular among Western consumers in recent years. “It is now produced by large multinationals and its accessibility has increased considerably. While yogurt is still consumed on a much larger scale, it is regarded by many as a dietary staple with many people consuming yogurt regardless of whether they feel the need to improve their gut health or not. Those that consume kefir generally do consume it specifically for its perceived health benefits.”
This is evidenced by UK supermarket Tesco recently stating its kefir sales have skyrocketed, as UK consumers gain a strong appetite for the ancient milk noted for its probiotic properties. Innova Market Insights data also shows a rising consumer interest in functional beverages and fermented products overall. This has marked its transition from the specialty sector to the mainstream with a heap of kefir NPD, such as organic kefir shots combined with functional ingredients.
Whether these study results could be replicated in human trials is “difficult to know for sure,” Dr. Cryan affirms, noting that more studies on the validation of kefir as a dietary intervention to improve humans’ mood are warranted.
“Furthermore, more people make kefir than yogurt at home and these consumers tend to be very passionate when discussing the merits of kefir,” Dr. Cryan concludes. Notably, the study highlights that the word kefir is derived from the Turkish word keyif, which translates as “good feeling.”