The human gut contains trillions of micro-organisms, bacteria and archaea. Little is known about the relationship between this gut flora or microbiome, and human health, but whereas the gut is susceptible to invasion by pathogens such as Vibrio cholerae (Cholera), Salmonella typhimurium (Typhoid) or Rickettsia prowazekii (typhus), most gut bugs, it seems, either do no harm or yield a positive benefit by aiding the process of digestion or by producing metabolites with positive effects on mental health or immune system function.
The common lactose fermenting organism, Lactobacillus rhamnosus, for example, produces large quantities of the mammalian neuroinhibitor, gamma amino butyric acid, or GABA, with apparently significant psychological effects. Feeding mice with L. rahmnosus produces measurable behavioral changes attributed to a reduction in anxiety, and at least one study with humans has yielded similar results.
Lacto-fermenting bacteria are reported also to suppress food and other allergies and to slow the progression of cancer. And you need no doctor's prescription to use these organisms: you can either buy them at the grocery store or raise them in your own pantry. Unpasterized yogurt, for example, contains the lacto-fermenting microbes: Lactobacillus bulgarius and Streptococcus thermophilus. A much wider, and probably more useful range of organisms is contained in Kefir (a drinkable milk product containing ten or more lacto-fermenting species). Other lacto-fermented products include Kimchi, and sauerkraut, both made chiefly or entirely from cabbage, and fermented drinks such as kvass, made from stale rye bread, beets, fruit juice or just about anything else containing starch or sugar, and Koumis, which is made by fermentation of mare's milk or camel's milk.
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