Probiotics are everywhere lately, and for very good reason.  Over the past few years much has been learned about the balance of probiotics (good or beneficial bacteria) and the role they play in our internal microbiome, the intestines.  We have good flora which we hopefully acquire at birth and which continue to grow and thrive throughout our life cycle.  These microorganisms then can protect us against bad bacteria, which are often introduced into our gastrointestinal tract via the mouth from being on or in our foods and drinks for example (or from licking fingers!)   What are normal flora?  What holds good and bad bacteria in check?   And just what do the good bacteria do for us?  There are so many benefits from probiotics it is impossible to outline them in one article, but from colon health and cancer prevention, to help with our immune system and production of key vitamins, probiotics work wonders for human health.  So read on to find out just how probiotics help our health and metabolism.

You might wonder how we obtain probiotics in the human intestines in the first place. One of the first sources is that they are obtained by contact with your mother as an infant.  Breast milk and breastfeeding, in particular, help foster the introduction and growth of probiotics.   There has been a fair amount of research recently with oligosaccharides, for example, which are complex sugars that feed good bacteria.  Oligosaccharides promote the growth of good gut bacteria and have been given the name “prebiotics.”  Oligosaccharides are present in breast milk and studies have found that breast-fed infants take in much more of them than formula-fed babies.  For adults, they are also present in plant foods, but more about that later.

When it comes to the many good and bad bacteria that enter our digestive tract, there is a “check and balance” system in place to guide and control their growth or destruction. We have our immune system; we have enzymes (made in the pancreas), acids (produced in the stomach) and bile salts (made in the liver and stored in the gall bladder) that are added into the gastrointestinal tract along with the all-important mucosal linings.  And we have the metabolic activities of bacteria themselves.

Bacteria in the Mouth and Stomach The first line of defense that helps control bacteria (especially potentially harmful bacteria on foods, etc) is the saliva in the mouth. Saliva helps control bacteria primarily by removing it from the mouth and sending it into the stomach. The very strong acid called HCl (hydrochloric acid) produced in the stomach is deadly to bacteria, and the bacterial count of digested food falls dramatically after a meal. So anything that happens to reduce HCL will allow more bacteria to survive.  If some bad bacteria survive, it could lead to problems, like foodborne illness for example.  New born infants and the elderly produce less HCL, and that’s why they are more prone to foodborne illness. In addition some illnesses and conditions or medications can lower the acid in the stomach.  So stomach acid is a very important first line of defense against pathogenic bacteria.

Bacteria in the Small Intestine The bacteria that survive the high acid content of the stomach will then pass on into the first section of the small intestine, called the duodenum. Here that the pancreas dumps digestive enzymes and bicarbonate into the intestines. The digestive enzymes from the pancreas protect us from harmful bacteria, such as E. coli, by digesting the cells walls of these bacteria.  Bile salts are produced in the liver and delivered into the small intestine also after a meal.  Bile salts are primarily for fat digestion and transportation, but they are also becoming known as potent as antimicrobial agents, so much so that they are being evaluated for use as antibiotics.  So when bile salts are altered within the duodenum it can lead to an overgrowth of some bacterial species. The bicarbonate from the pancreas raises the pH level of chyme (stomach contents). Because the pH is less acidic now, it allows for the growth of intestinal flora, so as food travels through the small intestine it gradually becomes more populated with good and bad bacteria. In addition to enzymes, bile salts, and the mucus secreted by the cells lining of the GI tract, peristalsis (muscular movements of the intestines) helps to keep the bacteria from adhering to the epithelial cells of the small intestines. This whole system is well designed to start achieving an environment where pathogenic bacteria are neutralized and good bacteria can thrive, but it can be easily disrupted. Drugs are a big potential disruptor – antacids lower HCL, there are drugs that slow peristalsis, and antibiotics are a huge disruptor of the balance of gut flora.  Even constipation can allow the gut to become colonized by harmful bacteria, simply because it allows the blend of flora to stay in the intestines longer.

So what are the microbes in our intestines? The predominant organisms are probiotics (like lactobacilli and Bifidobacteria) streptococci, staphylococci and yeasts. Lactobacilli like lactobacillus acidophilus, the most well know strain of probiotics, are a type of bacteria called gram-positive bacteria. Gram negative organisms such as Bacteroides and E. coli. also reside intestines.

Bacteria in the Large Intestine This is where most of the normal flora lives and there is a very high bacterial count. There are over 400 different species of bacteria numbering in billions in the large intestine. The ileocecal valve separates the small intestine from the large intestine.  This valve prevents the backflow of microorganisms from the colon into the small intestine, and therefore prevents high numbers of bacteria from backing up into the small intestine.  If too many bacteria are present in the small intestine, it can cause very uncomfortable gas after a meal.  Bacterial growth here is largely dependent upon availability of nutrients.

Even though there is extensive digestion and absorption that occurs in the small intestine, many nutrients still pass into the colon not yet completely digested.  Interestingly, some nutrients that stimulate some bacterial species like oligosaccharides simultaneously suppress the activities of other bacteria.  So, an extremely important factor governing bacterial composition in the large intestine is the types of food eaten and how much is digested or not in the small intestine.

Energy from Bacteria? The bacteria in our intestines obtain their energy by breaking down carbohydrates – a process called fermentation. The fermentation process produces substances called short chain fatty acids (SCFA’s). The short chain fatty acids produced by our gut flora are a tremendous source of energy for the cells that line the intestines (epithelial cells). SCFA’s are such an important source of energy for the cells that they will begin to die off if they don’t have them, so probiotics are important for the survival of intestinal epithelial cells. Other byproducts of probiotic activity in the intestines are vitamins.

Nutrients from Bacteria? Bacterial flora in the colon are involved in synthesizing hormone and vitamin precursors. One example is vitamin B12. The primary dietary sources of vitamin B 12 are animal products like meats and eggs. This vitamin is not found in any plant source, but it is produced by gut bacteria.  Vitamin B12 is essential for red blood cell function and is also required for nerve activities.  Deficiencies can lead to anemia and painful nerve disorders.  So adequate beneficial flora can be extremely important for maintaining B 12 levels, especially in vegans.

The Colon, Cancer and Microorganisms One of the most important SCFA’s produced by intestinal flora is butyric acid. Numerous studies have shown its affect on the growth and heath of intestinal epithelial cells.  Interestingly, butyric acid inhibits the growth of cancerous tumors. There is a direct relationship between the amount of butyric acid produced in the gut and colon/rectal cancer. In addition some bacteria in the colon actually neutralize dietary carcinogens such as nitrosamines, which can be produced when proteins are eaten or from sodium nitrates added to meats.

Most bacteria including bifidobacteria, lactobacilli, and Bacteroides prefer carbohydrates as their energy sources. They are well-adapted to breakdown complex sugars and to make many glycosidase enzymes. Since most of the sugars and carbohydrates from our meals have already been digested and assimilated into the blood stream in the small intestine, by the time the remaining food reaches the large intestine there are few nutrients left to feed probiotic bacteria. By adding probiotic-friendly foods to our diets we can dramatically increase healthy gut flora. The most probiotic-friendly foods are foods that are high in fiber and oligosaccharides. This is because they do not get totally digested; therefore, the flora in the large intestine use it to grow and thrive.

Bacteria are also very important for helping with final digestion of proteins.  Not all flora can breakdown proteins.  So . . .

• Stomach acids reduce the number of live bacteria in the intestinal tract.
• Digestive enzymes not only break down food, but also prevent bacterial overgrowth.
• Bile salts also help to protect against bacterial overgrowth in the small intestine.
• Friendly flora produce important B vitamins and other nutrients.
• The fermentation of food by probiotics creates short chain fatty acids which  inhibits the growth of pathogenic bacteria and feeds cells lining the intestinal tract.
• Balance of gut flora can be disrupted by low stomach acid, constipation, and medications.

These points are important because a lack of digestive enzymes combined with imbalanced gut flora can lead to related to gut inflammation, allergies, asthma, eczema autoimmune disorders, not to mention annoying gas and bloating after meals.

Today scientists have proven that probiotic organisms are essential for good intestinal health.  Besides all the other functions discussed in this article, they are particularly important because they help us fight off disease causing bacteria, such streptococcus, Clostridium and e coli, which can cause serious diarrhea and other problems such as urinary tract infections.

In summary, a great deal of important research is now being published which elucidates the pivotal roles probiotics have on not only intestinal health but our overall metabolism and health, including where your future health is headed. From depression to Type One diabetes, to autoimmune disorders, to cancer, the gut microbiome and the functions it performs, is finally gaining the attention it deserves.

But keeping the intestinal flora intact and balanced is no small feat. There are quite a few things that can disrupt the beneficial flora in the gut.

Some of the most common include:

• Drinking chlorinated tap water
• Several categories of Prescription
  and Over the Counter Medications
• Dietary choices
• Stress