Germs to the Rescue
Trankina, Michele L., The World and I
Populations of friendly bacteria that inhabit the large intestine protect us from attacks by pathogenic agents and alleviate the symptoms of a number of maladies.
Rarely do the words germs and rescue share the same billing. After all, have we not been repeatedly warned that germs are associated with contamination, disease, and unsanitary conditions? True, but we also know that all germs are not the same. In fact, scientists are discovering a growing list of microorganisms that silently contribute to making our world a better place. Many of these microbes are well known in food technology, and they are becoming increasingly conspicuous in the promotion of human health.
These beneficial germs that dwell in our digestive system are also referred to as friendly microflora, natural flora, and probiotics (from the Greek terms that mean "for life"). Rapidly accumulating literature attests to their roles in disease prevention and symptom relief. Over the past 10 years, numerous symposia and international conferences have underscored the clinical significance of probiotics, elucidating their features and potential applications for improving human health.
In defining the term probiotics, people from various disciplines-- particularly microbiology, biochemistry, and nutrition--have introduced their own nuances. Nonetheless, in a broad sense, probiotics may be defined as mixed cultures of live microbes (or products containing them) that, when ingested in sufficient quantity, exert beneficial effects on the health of the host. Probiotic products include fermented dairy and nondairy foods and supplements containing live bacteria, mainly of the genera Lactobacillus and Bifidobacterium.
When a probiotic product is ingested, the microorganisms it contains must be capable of surviving through the harsh conditions that prevail in most of the gastrointestinal (GI) tract. Some of them will eventually inhabit the lower part of the small intestine, while most will settle in the large intestine (colon). The colon is an especially suitable residence because of the relatively slow rate of passage of its contents compared with movement in the small intestine.
When populations of microflora are fully established, an average adult's colon contains upward of 400 species of micoflora, with 1011 bacterial cells per gram of colon contents. It is estimated that 20--40 percent of probiotic bacteria survive after ingestion and take up either permanent or temporary residence, depending on conditions.
Long history of usage
There is a long history of the consumption of fermented foods, along with specific recommendations for treating human illnesses. The Old Testament contains numerous references to eating curds, probably referring to yogurt. A Persian exegesis of Genesis 18:8 offers that "Abraham owed his longevity to the consumption of sour [fermented] milk."
Microbiologists have also long been aware of the importance of microbial homeostasis (balance) in the gut. The person most credited with recognizing the GI benefits of fermented foods is Nobel laureate Elie Metchnikoff of the Pasteur Institute, who ushered in the age of probiotics with his book The Prolongation of Life (1908). Metchnikoff proposed that the marked longevity of Bulgarian peasants was correlated with their intake of yogurt, produced by fermenting milk with microorganisms that generate lactic acid. He theorized that the lactobacilli (lactic acid bacteria) in yogurt kept pathogen populations in the peasants' intestinal tracts in check.
Goran Molin of Sweden's Lund University suggests that the consumption of fermented foods containing lactic acid bacteria was common until well into the twentieth century but then declined, leading to an increased incidence of GI maladies. The reduction of natural flora in the GI tract can also be attributed to several other factors: the widespread ingestion of antibiotics and other drugs by humans and animals raised for human consumption; food sterilization methods; and improvements in hygiene, along with the proliferation of antibacterial products. …