Gut flora - they take care of your immune system, but are you taking care of them?

• Appropriately balanced gut flora needed for healthy immune system
• Which bacteria reside in the gut?

Two pounds of bacteria in your gut!

The human intestinal tract is home to more than 400 species of bacteria weighing a total of ~2 pounds.    Concentration of bacteria increases dramatically from the stomach to the small intestine, to the colon. Bacteria comprise 1/3 dry-weight of feces.

Bacterial flora consist of aerobic and anaerobic species.    In a healthy large bowel, anaerobes outnumber aerobic bacteria by up to 1000 to 1.

-   Anaerobic flora is dominated by Bacteroides spp., bifidobacteria, propionibacteria and clostridia

-   Among aerobic bacterial flora, the Enterobacteria Escherichia coli, a facultative anaerobe (able to adapt to produce energy from glucose with or without oxygen) of the enterobacteriaceae family and Enterococci (another facultative anaerobe) predominate.   Note that most strains of E. Coli benefit the gut by producing vitamin K2 and keeping a check on pathogenic bacteria. It is only some of its serotypes (variations) that are pathogenic, and which can cause intestinal diseases E.g. food poisoning, UTIs and neonatal meningitis.

Appropriately balanced gut flora needed for healthy immune system

Studies are demonstrating the ability of the gut flora and oral probiotics to influence systemic inflammation, oxidative stress, glycemic control, tissue lipid content and even moods.    At least 60% of our immune system is located in our digestive system!

"Do you have a good "Gut feeling?" can be taken literally

 Since most SEROTONIN (the "feel-good"chemical) is produced in the gut.

Benefits of beneficial flora in GI Tract

A healthy balance of gut flora is generally considered to be 15% "unfriendly" bacteria vs. 85% "friendly"bacteria.    This ratio prevents the over colonization of disease causing micro-organisms (E.g. E. coliand Salmonella) and competes with and prevents the overgrowth of yeast and fungi.

-   Many lifestyle and environmental factors can upset this balance by harming the "friendlies"- such as:

•  Poor diet - excess sugar/fructose, processed foods/refined grains, herbicides/insecticides/pesticides;

•  Chlorinated/Fluoridated drinking and showering water

•  Too much alcohol

•  Pollution - industrial/household chemicals

•  Climate

•  Aging

•  Medication- especially antibiotics/anti-bacterial soaps (which destroy all bacteria - good and bad), contraceptive pill, and antacids

•  Illness

•  Stress

•  pH

•  Infection

•  Geographic location

•  Race

•  Socioeconomic circumstances

-   Symptoms that your "friendly bacteria" are "Losing the Battle", include:

•  Cravings for sugar and refined carb foods - the "unfriendlies"are insisting you feed them!

•  Gas and bloating / Nausea / Headaches

•  Constipation or diarrhea

•  Nausea

-   A large part of the influence of the "bad" bacteria is on the intestinal lining (mucosal barrier). The lining is over 300 square meters (about the size of a tennis court.)

-   For optimum intestinal flora balance, the beneficial LACTIC ACIDbacteria, such as the gram-positive Lactobacilli and Bifidobacteria, should predominate (Bifidobacteria account for ~ 90% of the total colonic beneficial microflora).    Presenting a barrier to invading organisms, they break down food carbohydrates to produce acids, such as lactic acid (break-down product of lactose). The most common of these lactic acid bacteria are:

•   LACTOacido bacillus   Inhabits both the small and large intestines

•   Bifidobacteria bifidum.    More prevalent in the large intestine, also the dominant species of the intestinal tract of breast-fed infants.

Which bacteria reside in the gut?

Upper GI Tract

Esophagus - contains only the bacteria swallowed with saliva and food

Stomach

Contains mainly acid-tolerant LACTOBACILLI

Stomach of ~50% of U.S. population have been colonized by the pathogenic bacteria Helicobacter Pylori.    Responsible for gastric ulcers and also most likely gastric and duodenal cancer

Small Intestine

The upper small intestine.   Contains relatively sparse GRAM-POSITIVE flora, consisting mainly of LACTOBACILLI and Enterococcus faecalis.This region has about 10⁵ - 10⁷ bacteria per ml of fluid.

The lower small intestine.   Contains 10⁸ bacteria /mlwith additional species including coliforms and Bacteroides

Large Intestine (Colon)

Colon contains bacteria similar to fecal bacteria

Bacteriallevels reach 10¹¹/ml feces

Modified from Youmans, et al.: The Biologic and Clinical Basis of Infectious Disease. W. B. Saunders Co. Philadelphia. 1985.

Reference