Wednesday, June 1, 2011
Healthy gut flora: bacteria from family, friends, Fido and food provide the foundation for the complex microbial community of the intestines, which controls the immune system. Antibiotics and hygiene are detrimental to gut flora and health.
Gut Flora Are Complex
Recent studies of the gut flora, e.g. the human gut biome, show that each individual maintains more than 150 different species of bacteria. Worldwide, that means that about a thousand different bacterial species are common residents of the human gut and together those gut bacteria use more than 1 million different genes. Many of those genes code for the enzymes used by gut bacteria to digest plant polysaccharides, i.e. soluble fiber.
Hygiene Isolates People from Healthy Sources of Gut Flora
Every time we speak, we release a mist of bacteria from our lungs, mouth and GI tract. These bacteria are on our skin, clothes and personal items, and provide a source of the bacteria that make us healthy. Parents and older siblings pass these bacteria on to younger children. These donated bacteria are essential for the development of a healthy immune system and children growing up with healthy relatives and exposed to soil bacteria via pets, farm animals, etc. are healthier than children who are more isolated.
In this sense, hygiene is unhealthy, because an individual is isolated from new sources of bacteria that could replace those lost by limited diets, antibiotics, etc. Otherwise, health is contagious, since gut bacteria from healthy individuals can spread among the population. Washing hands and food is unnatural and unhealthy.
Few Bacteria Make You Sick, but Many Are Essential for Good Health
Food intolerance can result from “good” family hygiene, limited diets and exposure to antibiotics. A common intolerance results from the absence of bacteria that produce an enzyme to digest dairy lactose, i.e. lactose intolerance. Lactose intolerance can be readily cured by eating a dairy product, such as yogurt, that contains both lactose and live bacteria (probiotics) that can digest the lactose. Simply eating moderate amounts of live yogurt daily for a couple of weeks resupplies the gut flora with bacteria that can digest lactose, and the intolerance is gone.
Soluble Fibers Are Plant Polysaccharides that Are Digestible by Bacterial Enzymes
Humans only produce enzymes to digest one polysaccharide, starch. All of the other hundreds of polysaccharides present in plants are only digestible by bacterial (and fungal) enzymes of the gut flora. If the bacteria and enzymes needed to fully digest a particular food polysaccharide are absent, then digestive problems ensue and the polysaccharide can act as a laxative. Continual eating of the problem food with a new source of diverse bacteria, e.g. lightly rinsed vegetables right from the garden, then the gut flora will incorporate new bacteria that can digest the problem polysaccharide and the gut is happy.
Soluble fiber feeds the gut bacteria that convert it into short chain fatty acids that nourish the colon. Constipation results from the absence of the bacteria needed to digest dietary fiber and to produce the large volume of bacteria that make up well hydrated stools.
Gut Bacteria Are Needed for Healthy Immunity
Cells of the human immune system are stored predominantly in the lining of the intestines. Intensive study of the interaction of the gut bacteria with the gut has revealed that both the aggressive half of the immune system that attacks pathogens and the suppressive half that protects the body itself from attack, develop in the gut in response to particular types of bacteria. Thus, the absence of one type of bacteria can cripple responses to infection, while other bacteria are needed to block autoimmune diseases and allergies. Most diseases are caused by disruption of the normal interactions between gut bacteria and the immune cells developing in the gut.
Antibiotics Lead to Autoimmunity
Antibiotics have dramatic and lasting impact on gut flora. Cattle treated with antibiotics and a high carbohydrate diet have an altered metabolism (obesity) that leads to rapid fat accumulation in their tissues. This is good for making tasty beef, but the same approach in people produces the suite of diseases in affluent societies.
Children treated with an antibiotic for a simple ear infection, are much more likely to return to pediatricians for treatments of subsequent obesity, infections and diseases. Compromised gut flora can take years to return to normal function after antibiotic treatment. Loss of the appendix, which is the normal source of bacteria to replenish gut flora after diarrhea, results in an increased risk of abnormal gut flora and numerous autoimmune diseases. It is likely that most autoimmune diseases are preceded by prior treatment with antibiotics that disrupted normal gut flora and permanently altered the immune system.
Interventions to Treat Disease: the Anti-Inflammatory Diet and Fecal Transplants
It should be obvious that a disrupted or unhealthy gut flora will compromise the immune system and contribute to disease. Treatment of diseases is complicated by the use of drugs that also impact the gut flora and produce additional side effects. An alternative approach would be to support the healthy gut flora and normal development of the gut immune system. As always, the answer is a supportive diet and a source of gut bacteria. The diet is obviously the Anti-Inflammatory Diet that provides support for almost anything that ails you. Probiotics are not retained in the gut, but they can contribute a few of the genes needed for a healthy gut flora. The source of bacteria for a healthy gut flora may range from minimally washed garden vegetables, to the more aggressive total replacement of gut flora with a fecal transplant from a healthy donor.