Article by John McDougall author of Dr. McDougall’s Digestive Tune-Up.

Within our intestines live trillions of organisms that are so important to our health and survival that they should be thought of as a vital organ—just like our livers or kidneys.

The gut microflora is the name we give to this living factory, whose beneficial functions include: completing the digestion of our foods through fermentation, protecting us against disease-causing microbes, synthesizing water-soluble vitamins, and stimulating the development and function of our immune systems.

Our intestinal tracts contain a complex and diverse society of disease-causing (pathogenic) and “friendly” bacteria. Rule number one is simple: dominance by the “good guys” will crowd out and leave no room in our intestines for the “bad guys.” In addition to digesting remnants of our meals and synthesizing vitamins, the helpful bacteria play an important role in the development of the immune system by maintaining a constant dialogue with our internal bodies through the surface of the gut. Our microflora also influence many of our hormones.

The health consequences from an imbalance of our sex hormones can lead to precocious puberty, fibrocystic breast disease, PMS, uterine fibroids, prostate enlargement, and breast, uterine, and prostate cancer. When our bowel bacteria really get out of control, severe forms of colitis and colon cancer can be the consequences.

Bacteria are not distributed randomly throughout the intestinal tract but are found in different numbers and kinds in different regions of the gut. The mouth provides a fertile garden for millions of bacteria, but the stomach (because of the acid) and small intestine contain a very low level of bacteria. The final five feet of the intestine, known as the large intestine or colon, works as a microbial factory, with more than five hundred different species of bacteria living in a three-pound (1.5 kg) mass of partially digested matter. Within the colon the concentration of bacteria reaches one trillion organisms per gram (1/30th of an ounce) of feces. Bacteria make up about 60 percent of the weight of the feces. The microflora are so important to our well-being that after a person’s colon is surgically removed (colectomy), the last part of the small intestine (ilium) takes over this vital role and becomes colonized with a similar biomass of bacteria.

The health of the flora can become impaired by temperature, illnesses, antibiotics and other drug treatments, and changes in our diets. The effects of antibiotic therapy can be profound and persistent, even causing a life-threatening infection with overgrowth of pathogenic bacteria (called Clostridium difficile).

Before birth, the gastrointestinal tract of a normal fetus is sterile. When the newborn passes through the birth canal, he or she is inoculated with organisms from the mother’s vagina and bowel. Benefits to the infant begin immediately with this natural defense barrier of “friendly” bacteria standing against harmful microbes that will enter later on with touching, suckling, kissing, and caressing.

The importance of this early invasion of friendly bacteria should not be underestimated. Its presence or absence makes a permanent impression on the immune system, thereby affecting a person’s well-being throughout his or her life. Newborns delivered by cesarean section do not get a healthful dose of the mother’s bacteria.

Born through the abdomen, much of their initial bacteria come from the unhygienic environment of a hospital. However, this setback can be remedied by the initiation of proper infant feeding after birth—and boosted by the addition of infant probiotics

Breast-feeding encourages the growth of “friendly” bacteria known as Bifidobacterium. These vital organisms protect the baby from gastrointestinal infections that can result in illnesses severe enough to require hospitalization and sometimes cause death. Mother’s milk contains sugars (galactooligosaccharides) that encourage the growth of these friendly bacteria. By the fourth day of life, Bifidobacterium represent 48 percent of the bacteria in breastfed infants as opposed to 15 percent in bottle-fed infants.

Eventually, over 95 percent of the bacteria become Bifidobacterium bacteria in an exclusively breast-fed baby. Introduction of small amounts of formula to a breast-fed baby will result in shifts from a breast-fed to a formula-fed pattern of the microflora. After weaning from breast milk—ideally after the age of two years—the child’s flora becomes similar to an adult’s.

How do healthy microflora thrive? The microflora in our large intestines thrive on the partially digested remnants of our meals—they eat what we eat. The microflora require approximately 250 calories of carbohydrate daily just to survive. Each species of bacteria survives best on specific kinds of nutrients. In short, friendly bacteria prefer dining on plant-food remnants, and pathogens prefer eating meat and other “junk-food.” Therefore, what we choose to eat determines the predominance of the bacteria species that will live in our gut—friendly or pathogenic. By eating a diet based on whole plant foods rather than on animal foods and highly processed foods, you can suppress the growth of harmful bacteria and stimulate the growth of those that are beneficial. If your current diet is one that feeds the pathogenic bacteria, take heart. Major alterations in the microflora take place within one to two weeks of a healthful diet change.

Bacteria enjoy the parts of the plant foods that we don’t use. Undigestible complex carbohydrates (dietary fiber) and other smaller undigestible sugars (oligosaccharides) provide the bulk of the food for our bowel bacteria. Only plants contain these complex and simple carbohydrates (except for breast milk, as noted above). These undigestible simple sugars are abundant in artichokes, onions, chicory, garlic, leeks, and, to a lesser extent, cereals. Beans, peas, and lentils contain the oligosaccharides raffinose and stachyose that feed our friendly bowel bacteria. Purified wood cellulose, which has been used to manufacture some “high-fiber breads,” is not broken down by the microflora. Because only plants contain these microflora-nourishing sugars, strict vegetarians (vegans) have been found to harbor much higher counts of “friendly” bacteria than do meat-eaters.

Manipulating Our Microflora with Probiotic Supplements The buzzword “probiotics” will be popping up more and more as health-conscious individuals become increasingly aware of the role of gut microflora. Probiotics are used for the purpose of adding a particular species of bacteria in order to rebalance the intestines and thereby improve a person’s health. Probiotics are sold as foods and pills (supplements) that contain millions of friendly bacteria and sometimes yeast. Purchased in natural food stores, probiotics are usually found in the refrigerated section. Some are labeled as “ newborn formulas,” while others are aimed at improving the flora of a child or an adult. Probiotics have no toxic effects.

Ahealthy microflora is necessary for overall health—period. Anyone who wants to be healthy should encourage the growth of healthy microflora by eating the right foods and avoiding antibiotics (which kill both good and bad bacteria) whenever possible. This means a “ breast-milk diet” for infants and a healthful plant-based diet (like the McDougall Diet) for children and adults.

Newborns delivered by cesarean section and bottle-fed babies may benefit from probiotics specifically designed for infant use. Probiotics may also be warranted after a course of prescribed antibiotics in order to help reestablish a healthy gut flora. Probiotic supplements, in addition, may prove beneficial if you have changed your diet and still suffer from problems such as irregular bowel movements, indigestion, elevated cholesterol, or arthritis. With no undesirable side effects and minimal cost, you have everything to gain and nothing to lose by trying probiotic supplements.

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