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A Wonderful Colon |
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The Comfortable Past
Many years ago in medical school, there was not much to teach about the colon. We knew it was filled with bacteria, perhaps 300-400 types. The liquid stool entered it from the small intestine. Water was extracted from the stool so that when it arrived in the rectum, you had, hopefully, a soft, once-a-day stool pattern. It was a pretty uncomplicated process and organ. We spent most of our time studying the diseases of the colon such as irritable bowel syndrome, diverticulosis, Crohn's disease, ulcerative colitis and colon polyps and cancer. The idea that the colon was a quiet health producing organ was totally foreign. The colon, in those days, was simply a receptacle that held the waste the body did not use until it could be evacuated. Pretty simple and pretty wrong.
What We Now Know About Food Fiber
 During my years in practice, I was a firm advocate of increasing food fiber in the diet. I was aware of the work of researchers in Africa who discovered that rural Africans who consumed a largely plant grown diet with lots of fiber had 2-3 large, soft bowel movements a day. In addition, they seldom had diseases of the colon, as mentioned above, that are so common in the Western world. A high fiber diet made sense to me and many of my patients were relieved of constipation and simply felt better on such a diet. Further, some epidemiologic studies began to show significant health benefits when fiber was significantly increased in the diet, including heart disease and cancer. Still, it seemed that this was the end of the fiber story. Little did I know!
There are many types of fiber that have been discovered in plants, including various types of starches, lignins, cellulose and others. These were of interest to plant chemists, but not of much interest to physician. Then in the 1980s, it was discovered that fiber could broadly be separated into insoluble and soluble types. No fiber is digested by the small intestine. All of it arrives into the colon unchanged. Insoluble fiber does not dissolve in water, is not fermented or broken down by colon bacteria, but does retain lots of water in the colon and so provides a larger, softer stool. Soluble fiber, on the other hand, is broken down and fermented by colon bacteria. We really didn't know too much more about these two types of fiber until the 1990s when better measuring methods were devised. In the last 15 years, the difference between these two fibers, insoluble and soluble, has become increasingly important, especially with the discovery of the prebiotic soluble fibers.
Microbiota - The Glorious Cauldron of Colon Bacteria
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In the recent past, researchers and we physicians have come to understand the makeup of the colon bacteria to a remarkable degree. Microbiologists have been able to isolate and grow some 300-400 different bacteria from the colon, along with some viruses and yeasts - all entirely normal to find in the colon. In the past year, complex microprobes have been able to detect the makeup of the protein in the wall of bacteria. Each type of bacteria has a specific protein makeup in their wall. Amazingly, it has been found that there are likely over 1,000 different bacteria growing in the colon, twice the number previously known. So, we have only been able to culture by previous techniques perhaps just half the bacteria in the colon. In addition to that, the total number of bacteria in the colon is measured to be many trillions, at least 10 times the number of cells in the entire body. It gives you pause when companies that sell probiotic bacteria products claim that they have 5 or 10 billion bacteria in a pill, an incredibly small number compared to what is already in the colon.
Here is a final fact to consider. There is no place in the world, no organ or colon in any other animal or fish where there is such a tightly packed collection of bacteria, as in the human colon. This is normal. So, the question must be - why do humans have this incredible collection, this glorious, chaotic tightly packed mix of bacteria as a normal part of our bodies? The answers are slowly coming in. They are incredibly surprising and exciting to scientists and physicians. The story can be best understood by knowing something about prebiotics.
Prebiotics
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 Prebiotics are really the new kid on the block. The term was just coined in 1995. A prebiotic is a special type of soluble fiber that is used mostly by the beneficial good bacteria as a fuel. These good bacteria, in turn, produce certain substances that acidify the colon (a very good thing) and that serve as a fuel nutrition source for the colon's own cells. Isn't this remarkable? The colon provides a warm, oxygen-free environment for these beneficial bacteria to grow. These bacteria, in turn, manufacture the nutrition source for the colon itself. This is a true symbiotic relationship where both the bacteria and colon depend on each other and promote each others health. Of course, the body benefits even more as some, rather remarkable health benefits occur when this system is operating maximally.
So what are these Prebiotics? The ones with the most science behind them are inulin and oligofructose. Inulin, itself, is remarkable in that it has been around in the plant world for a very long time. It has been found in over 36,000 different plants, so it somehow has been a vital food source for plant-eating animals and humans for a very long time. Interestingly, as our food industries and agriculture have developed, the foods in which we get inulin have become limited. We now find them in:
| wheat |
onions |
| bananas |
garlic |
| leeks |
chicory root |
| Jerusalem artichokes |
wild yam |
| agava |
jicama |
In the U.S., most people get very little of this valuable fiber, perhaps only 2-3 grams a day on average with 70% of this coming from wheat and 20% from onions. Europeans eat three to five times this amount of inulin containing foods.
A prebiotic should do three things:
- It is not digested by the small intestine
- It is used as fuel, or fermented, by some colon bacteria
- It produces beneficial health benefits by objective measurements
According to some leading authorities, only inulin and oligofructose have fulfilled these three criteria. However, there are likely prebiotics coming along such as:
- Galacto oligosaccharide (GOS) - from milk
- Xylo-oligosaccharide - from wood pulp
- Isomalto-oligosaccharide (IMO) - from corn and wheat
- Soybean
- Barley food extract
So, these prebiotics fibers are a relatively newly discovered fiber. More than this, they have been found by careful research to provide significant health benefits, not only to the colon but to the body as a whole.
For a full essay on Prebiotics click here
The Colon as a Health Organ
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 The colon, as a health organ, is an incredible idea. Who would have thought it? Facts, however, have a way of pushing themselves in front of you and, sooner or later, you just have to pay attention. So, here are some facts about what prebiotics do when they are acted on by the good bacteria in the colon. These facts are supported by research. Some of it is hard, meaning that there is a lot of support in the research community. Some is soft, where there is early work showing benefits but more is needed. So consider the following outcomes for the body when prebiotics, either in food or supplements, are taken in adequate doses.
- Increased probiotic growth. Yes, the probiotics you take need nourished by prebiotics
- Improved bowel regularity-softer and more regular BM
- Increased absorption of calcium and magnesium through the colon
- Increased, stronger bone density. This is particularly true for young teenagers
- Enhanced well defined immune facors in the colon
- Reduced colon and polyp carcinogen (cancer causing) factors
- Reduced triglyceride level
- Reduced allergies and asthma, especially in infants and children
- Controled appetite and reduced weight
- Dramatically increase the growth of the good colon bacteria, Bifidobacter and Lactobacillus. These are very protective.
- Decreased growth of bad colon bacteria, Clostridium and others
- Decreased or cessation of offensive flatus smell
Well, there are other benefits suspected from prebiotics, but you get the picture. There are a lot of healthy things happening when you get adequate inulin and oligofructose in your diet and/or supplements.
Is There a Downside to Prebiotics?
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The beneficial bacteria, Lactobacillus and Bifidobacter, do not make colon gases. However, other gas-forming bacteria will metabolize prebiotics as well. So, early on there may be some excessive colon gas and flatus. The way to handle this is to start at a smaller amount of the foods or supplements. Then increase the amount every few days until a satisfactory outcome is reached.
The Future of Prebiotics and Colon Health
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 No one should be rash enough to predict the future. However, it is always fun to close your eyes and think what might be. As a nation, we in the U.S. have reached a bizarre, almost schizophrenic, stage. Our food manufacturers have doused us with calories and high fructose corn syrup. We have an epidemic of obesity, undoubtedly with very poor underlying body nutrition. At the same time, Americans are living longer for a variety of reasons. Further, I am impressed that so many younger people seem to be shifting to, what I would judge to be a better-balanced diet with less red meat and increased vegetables and fruits. And further still, I see so many young people, especially the girls and young women, who are aggressively taking care of their own health.
So, there are pluses and minuses. In my more comfortable field of gastroenterology, I would dearly like to see prebiotics assume a role in the dietary management of many of the colon disorders we see. There is no downside, aside from excess colon gas if too much is used, and there may be great benefits. Just this past month, a friend with ulcerative colitis told me that since starting prebiotics, his bowels are regular, he feels better, he has reduced his medication and his malodorous flatus (hydrogen sulfide) no longer smells (see Ulcerative Colitis Dietary Therapy). This is one person and one case proves nothing. No one with any colon disorder should make dietary changes without advice from their physician. However, putting this information together has been incredibly stimulating. If, over time, these prebiotics food fibers can make a gradual improvement in the public's health, to say nothing of those with gastrointestinal problems, then my own medical career will have been topped off beyond my dreams.
Medical References
The bacteria colonizing the human intestinal tract exhibit a high phylogenetic diversity that reflects their immense metabolic potential. By virtue of their catalytic activity, the human gut micro-organisms have an impact on gastrointestinal function and host health. All dietary components that escape digestion in the small intestine are potential substrates of the bacteria in the colon. The bacterial conversion of carbohydrates, proteins and nonnutritive compounds such as polyphenolic substances leads to the formation of a large number of compounds that may have beneficial or adverse effects on human health.
PURPOSE OF REVIEW: To highlight mechanisms whereby diet affects colonic function and disease patterns. RECENT FINDINGS: Topical nutrients are preferentially used by the gut mucosa to maintain structure and function. With the colon, topical nutrients are generated by the colonic microbiota to maintain mucosal health. Most importantly, short chain fatty acids control proliferation and differentiation, thereby reducing colon cancer risk. In patients with massive loss of small intestine, short chain fatty acid production supports survival by releasing up to 1000 kcal energy/day. Human studies show that the microbiota synthesizes a large pool of utilizable folate which may support survival in impoverished populations. Unfortunately, the microbiota may also elaborate toxic products from food residues such as genotoxic hydrogen sulfide by sulfur-reducing bacteria in response to a high-meat diet. The employment of culture-free techniques based on 16S regions of DNA has re vealed that our colons harbor over 800 bacterial species and 7000 different strains. Evidence suggests that the diet directly influences the diversity of the microbiota, providing the link between diet, colonic disease, and colon cancer. The microbiota, however, can determine the efficiency of food absorption and risk of obesity. SUMMARY: Our investigations have focused on a small number of bacterial species: characterization of microbiota and its metabolism can be expected to provide the key to colonic health and disease.
The terms intestinal "microflora" or "microbiota refer to the microbial ecosystem colonizing the gastrointestinal tract. Recently developed molecular biology instruments suggest that a substantial part of bacterial communities within the human gut still have to be described. The relevance and impact of resident bacteria on the host physiology and pathology are, however, well documented. The main functions of intestinal microflora include (1) metabolic activities translating into energy and nutrients uptake, and (2) host protection against invasion by foreign microorganisms. Intestinal bacteria play an essential role in the development and homeostasis of the immune system. Lymphoid follicles within the intestinal mucosa are the main areas for immune system induction and regulation. On the other hand, there is evidence implicating intestinal microbiota in certain pathological processes including multi-organ failure, colon cancer, and inflammatory bowel disease.
The microbiota of the human intestinal tract play an important role in health, in particular by mediating many of the effects of diet upon gut health. Surveys of 16S rRNA sequence diversity in the human colon have emphasized the low proportion of sequences that match cultured bacterial species. This may reflect limited recent effort on cultivation rather than inherent unculturability, however, as anaerobic isolation methods can apparently recover a wide range of the diversity found. A combination of information from representative cultures, molecular tools for enumeration and tracking of bacterial metabolites offers the most powerful route to understanding the roles played by different groups of bacteria in the gut ecosystem. Progress is being made for example in defining key functional groups including primary colonizers of insoluble dietary substrates, and major contributors to metabolites such as butyrate that influence the health of the gut mucosa. There is in creasing evidence that bacterial populations in the large intestine respond to changes in diet, in particular to the type and quantity of dietary carbohydrate. A general consequence of increased carbohydrate consumption is to reduce the pH of the gut lumen, which is likely to play a major role in determining bacterial metabolism and competition. Oligosaccharides used as dietary prebiotics must inevitably have complex effects upon the bacterial community that include non-target organisms and the consequences of metabolic cross-feeding and changes in the gut environment.
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