NUTRITION AND GASTROINTESTINAL FLORA

Nutrition and Gastrointestinal Flora

Nutrition and gastrointestinal Flora

Introduction

The gut flora consists of the microorganisms that normally live in the digestive tract of animals. The gut flora includes much of the human flora. The term "gut flora" is interchangeable with intestinal microflora and intestinal microbiota.

Biological Basis

The average human body, consisting of about 1013 (10,000,000,000,000 or about ten trillion) cells, has about ten times that number of microorganisms in the intestines. The metabolic activity performed by these bacteria is equal to that of a virtual organ causing some to describe the gut bacteria as a "forgotten" organ (Schwiertz, 2003).

Bacteria make up most of the flora in the colon and 60% of the dry mass of feces. This fact makes feces an ideal source to test for gut flora for any tests and experiments by extracting the nucleic acid from fecal specimens, and bacterial 16S rRNA gene sequences are generated with bacterial primers. This form of testing is ideal when compared to more invasive techniques, such as biopsies. Somewhere between 300 and 1000 different species live in the gut, with most estimates at about 500. However, it is probable that 99% of the bacteria come from about 30 or 40 species. Fungi and protozoa also make up a part of the gut flora, but little is known about their activities (Bettelheim, 2004).

Research suggests that the relationship between gut flora and humans is not merely commensal (a non-harmful coexistence), but rather is a mutualistic, symbiotic relationship. Though people can survive with no gut flora, the microorganisms perform a host of useful functions, such as fermenting unused energy substrates, training the immune system, preventing growth of harmful species, regulating the development of the gut, producing vitamins for the host (such as biotin and vitamin K), and producing hormones to direct the host to store fats. However, in certain conditions, some species are thought to be capable of causing disease by causing infection or increasing cancer risk for the host.

The gastrointestinal tract of a normal fetus is sterile. During birth and rapidly thereafter, bacteria from the mother and the surrounding environment colonize the infant's gut. Immediately after vaginal delivery, babies have bacterial strains in the upper gastrointestinal tract derived from the mothers' feces (Schwiertz, 2003). Infants born by caesarean section may also be exposed to their mothers' microflora, but the initial exposure is most likely to be from environmental microbes such as the air, other infants, and the nursing staff which serve as vectors for transfer. The primary gut flora in infants born by cesarean delivery may be disturbed for up to 6 months after birth whereas vaginally born infants take up to 1 month for their intestinal micro flora to be well established. After birth, environmental, oral and cutaneous bacteria are readily transferred from the mother to the infant through suckling, kissing, and caressing. All infants are initially colonized by large numbers of E. coli and streptococci (Bettelheim, 2004). Within a few days, bacterial numbers reach 108 to 1010 per gram of ...