While fermented milk might not immediately appeal to every palate, the United Kingdom is witnessing an extraordinary surge in consumption of this traditional beverage, commonly known as kefir. Market data reveals skyrocketing sales figures, with major supermarkets reporting unprecedented growth. However, alongside this rapid rise in popularity, healthcare professionals are noting a corresponding increase in patients reporting adverse reactions to the probiotic drink.
The Ancient Drink's Modern Renaissance
Kefir boasts a rich history spanning thousands of years, with origins tracing back to the Caucasus Mountains region of Russia and Mongolia. This fermented dairy product has experienced a remarkable resurgence in recent years, largely driven by widespread promotion of its purported health benefits. In 2024 alone, retail giant Tesco documented a staggering 400 percent increase in kefir sales compared to just eighteen months prior, highlighting the beverage's dramatic market penetration.
The drink's appeal lies in its impressive microbial content, containing billions of beneficial bacteria often described as friendly microbes that support digestive system function. Scientific research indicates that maintaining elevated levels of these microorganisms within the gut can yield extensive positive health outcomes. These potential benefits include reduced risks of cardiovascular disease, obesity, various infections, and even colorectal cancer.
Kefir presents as a fermented milk beverage with consistency similar to thin yogurt, gaining traction primarily due to its gut health advantages. Nutritionally, consuming just 250 millilitres provides approximately 40 percent of an adult's daily calcium requirements, adding to its nutritional profile.
Expert Perspectives on Kefir's Benefits
Jordan Haworth, a digestive health specialist at The Microbiome Clinic in London, which provides gut microbiome testing services, shares his personal practice: "I drink kefir every day. It's arguably a superfood. The beverage contains about ten to twenty times more beneficial bacteria than standard yogurt, alongside substantial protein, calcium, and various essential vitamins."
Understanding the Potential Risks
Despite these apparent advantages, medical experts emphasise that kefir consumption carries certain risks that consumers should carefully consider. Some individuals may experience uncomfortable digestive side effects from introducing the fermented drink into their diet. For others, kefir might exacerbate pre-existing medical conditions. In extremely rare circumstances, the beverage could potentially trigger serious infections requiring medical intervention.
Gradual Introduction Recommended
Healthcare professionals caution against consuming excessive quantities of kefir too rapidly. The sudden influx of bacteria into the digestive system can provoke painful symptoms, according to experts. Kefir production involves combining aged milk with grains rich in bacteria and yeast, typically resulting in around two billion microbes per standard serving.
While long-term consumption may enhance gut health, short-term negative effects can occur, explains Mr Haworth. Research indicates that first-time kefir drinkers frequently develop gas, bloating, abdominal cramps, diarrhoea, or loose stools. This reaction occurs because newly introduced bacteria begin fermenting carbohydrates present in the gut, such as those from bread or pasta, producing excess gas as a byproduct.
Experts recommend starting with small kefir portions and gradually increasing dosage over time to mitigate these issues. "It's best to start low and go slow with kefir," advises Mr Haworth. "Most people should tolerate a small glass daily without difficulty, whereas a large glass could potentially cause digestive problems."
Potential Aggravation of Existing Conditions
Although frequently promoted as a digestive panacea, kefir may actually worsen certain gastrointestinal disorders, according to medical specialists. Irritable bowel syndrome, affecting approximately one in ten British adults and characterised by abdominal pain and diarrhoea, represents one such condition. While some evidence suggests probiotic-rich beverages might alleviate IBS symptoms for patients with depleted beneficial gut bacteria, others experience opposite effects.
The increased gas production resulting from enhanced carbohydrate fermentation can further irritate already sensitive bowel linings. Similarly, kefir consumption may exacerbate symptoms for individuals with small intestine bacterial overgrowth, where excess bacteria in the small intestine causes gas accumulation leading to bloating, pain, and diarrhoea.
"Kefir can lead to bloating in IBS and SIBO patients," confirms Mr Haworth. "Complete avoidance isn't necessarily required, but limiting consumption is advisable for affected individuals."
Rare But Serious Infection Risks
In exceptional cases, probiotics including kefir can precipitate dangerous infections. For patients with severely compromised immune systems, bacteria introduced through the beverage might cause bodily harm. Japanese physicians recently documented a case where a patient died after consuming a probiotic supplement similar to kefir.
A medical review published in the British Medical Journal detailed how a seventy-year-old man initially hospitalised with COVID-19 and an unrelated bacterial infection was advised to take probiotics for ongoing gut issues during recovery. Two months later, he required readmission with severe abdominal pain caused by internal swelling from infection. Blood tests revealed Clostridium butyricum bacteria—identical to that in his probiotic supplement—as the causative agent.
The patient developed sepsis, triggering organ failure and eventual death. Medical professionals attributed his vulnerability to long-term alcohol abuse combined with COVID-19 infection, which allowed probiotic bacteria to spread systemically. Consequently, experts recommend that individuals with serious underlying health conditions—including HIV, organ transplants, or recent cancer treatments—consult medical professionals before incorporating kefir into their diets.
As kefir continues its remarkable ascent in British dietary habits, balanced understanding of both its potential benefits and possible risks remains crucial for consumers seeking to optimise their gut health through fermented foods.
