Fermented foods, such as kefir, kvass, yogurt and sauerkraut, are considered to be healthy, as they contain prebiotics. However, fermented foods can be dangerous for some people.
Flatulence or bloating
After eating fermented food, there is often a slight temporary excessive flatulence. Microbiologist Manal Mohammed from the University of Westminster claims that this may be due to the fact that the intestinal microbiome change under the influence of probiotics. Excessive flatulence will pass over time, but it can cause serious discomfort to some people.
Probiotics are not dangerous for most people, but there are some rear cases when bacteria cause infection in people with weak immune system.
Fermented foods with probiotics may contain the so-called biogenic amines - histamine and tyramine, which are produced when bacteria ferment proteins. Some people may be sensitive to these substances, and eating fermented foods can cause a headache.
Fermented foods often contain histamine, a mediator involved in allergic and inflammatory reactions. We usually are able to digest it, but sometimes it can be absorbed in the gastrointestinal tract and enter the bloodstream, which can lead to the development of symptoms of histamine intolerance.
Useful probiotic bacteria may contain antibiotic resistance genes. Such genes can be transmitted from one bacterium to another. Thus, seemingly useful probiotics can theoretically contribute to the spread of antibiotic resistance.