Thanks to the promotion of their beneficial effects on gut health, the demand for fermented foods has skyrocketed and become unprecedentedly popular. According to the British "Daily Mail," fermented foods are prepared and produced using bacteria or yeast to break down natural sugars; some, such as yogurt, contain probiotics known to be strains of bacteria beneficial to gut health. Other fermented foods undergo pasteurization, smoking, baking, or filtering. Although these methods can kill live bacteria, they still offer health benefits, such as kimchi—a traditional fermented food kept in a cool place—providing lactic acid that boosts the immune system; while sourdough bread offers important fiber for gut health.
**Potential Benefits**
Bahi van de Poer, a nutritionist and spokesperson for the British Nutrition Society, states: "Fermentation was originally used as a method of food preservation, but these days, fermented foods are made to obtain their potential health benefits." Fermented foods are promoted as a primary means of increasing "good" gut bacteria and enhancing diverse microorganisms associated with improved digestion, reduced inflammation, strengthened immunity, and mental health.
**Health Warnings**
Experts are currently warning that some individuals—especially those with weakened immune systems—should be cautious about consuming them. The warning follows a recent finding from Ohio State University that certain fermented foods, such as kimchi and artisanal cheese, contain antibiotic-resistant bacteria. These bacteria can cause symptoms related to the gut, such as vomiting and diarrhea, or even more severe health issues, like potential deadly sepsis, if they enter the bloodstream.
**Dangerous Bacterial Strains**
It was found that one type of kimchi tested in the study contained a strain of Vancomycin-resistant bacteria, which is associated with severe infection cases like endocarditis and osteomyelitis, and even exposure to death. Most serious cases occur among those who already have weakened immune systems and some undergoing chemotherapy. Dr. Manal Mohammed, a prominent lecturer in medical microbiology at the University of Westminster, notes that certain strains of this bacteria are linked to resistance to many antibiotics.
**Drug-related Illness**
Researchers point out that those who are more likely to consume more fermented foods—for example, in an effort to boost gut health after illness or a course of antibiotics, which kills both good and bad bacteria—are particularly vulnerable to antibiotic-resistant bacteria because their immune defenses are low.
**Probiotic Supplements**
Van de Poer advises: "In this scenario, it is safe to take supplements of specific probiotic strains to restore gut health," which are effective in preventing infection-related diarrhea, such as Lactobacillus rhamnosus and Saccharomyces boulardii yeast. It’s essential to consider that specific probiotic types can provide targeted benefits, such as reducing antibiotic-associated diarrhea, abdominal pain, and bloating linked to irritable bowel syndrome, as well as improvement in gas and bowel regularity in adults.
**Spread of Infections**
Dr. Manal Mohammed states that the discovery of antibiotic-resistant probiotics in fermented foods is "extremely concerning," as feces contaminated with bacterial infections can "help spread antibiotic resistance in the environment," indicating that consuming antibiotic-resistant probiotics may lead to the accumulation of antibiotic resistance genes in some individuals.
**Histamine Intolerance**
Van de Poer explains that "some fermented foods are high in histamines, which can lead to symptoms including headaches, rashes, and digestive issues in people with histamine intolerance," a condition affecting about 3% of the world's population, which is a type of allergy that occurs due to a buildup of histamine in the body and a deficiency in the enzyme that breaks down histamine to perform multiple functions in the body.
