Human health depends on intestinal health. The body requires intestinal bacteria for numerous protective, structural and metabolic roles.
Over 100,000 billion bacteria from 500 species live in the human gut, collectively called the intestinal flora or gut flora. The type and number of bacteria varies on a daily basis, as the body is subjected to bacteria from food and the environment. It is important there are optimal numbers of all bacteria and a greater balance of good or beneficial bacteria versus bad or disease causing bacteria. The beneficial bacteria are called probiotic bacteria.
Probiotic means pro-life. The scientific definition from the Food and Agriculture Organization of the United States and World Health Organisation is: “probiotics are live microorganisms that when administered in adequate amounts confer a health benefit on the host.”
Types of Beneficial Bacteria that Maintain Intestinal Health
Most of the intestinal bacteria live in the distal (end) of the small intestine and the large intestine (colon). The bacteria in these areas make up 60% of the fecal mass. The top and middle parts of the small intestine and stomach are rich in acid, bile and pancreatic secretions, which can destroy the bacteria, so fewer numbers are found there.
The most common bacteria found in the intestines are:
- Bifidobacterium
- Clostridium
- Bacteroides
- Eubacterium
- Escherichia
- Enterococcus
- Lactobacilli
- Streptococcus
- Klesiella.
Colonisation with Intestinal Bacteria
The intestine is not colonised with gut bacteria until after birth. A baby's body is completely sterile until it travels through the vaginal canal or is exposed to the hospital environment. Many factors such as breastfeeding and bottle-feeding, medications, and the environment affect the type of intestinal bacteria that first colonise a child’s intestinal tract. After weaning, or formula introduction, and by the age of two, infants develop a stable intestinal flora similar to that of an adult.
Factors Affecting Our Intestinal Flora
The adult intestine has a stable core of bacteria that is governed mainly by genetics. There are also transitory bacteria that travel through the gut without establishing themselves on the gut wall.
Factors such as diet, antibiotic use, environmental influences, aging, and stress can negatively affect these transitory bacteria.
Alteration of the core bacteria occurs, but should rebound to its original core over time. However, M. F. De La Cochetiere et al. (2005) found in the study ‘Resilience of the Dominant Human Fecal Microbiota upon Short-Course Antibiotic Challenge’ published in the Journal of Clinical Microbiology, that after antibiotic therapy the core might not rebound back to the original state in the appropriate time. Therefore, antibiotic therapy may cause some individuals to suffer reduced intestinal health, and taking a probiotic supplement would be advisable.
Probiotic Bacteria - an Overview
For human health, probiotic bacteria should meet the following minimal criteria:
- Must be purified
- Must be identified at genus, species and strain level
- Are shown in human trials to improve some parameter of human health
- Are safe.
Probiotic bacteria are named according to the genus, species and strain.
Some examples include the following:
- Lactobacillus acidophilus LA5—Lactobacillus is the genus, acidophilus the species and LA5 the strain.
- Another member of the Lactobacillus genus is Lactobacillus plantarum 299v—Lactobacillus is the genus, plantarum the species and 299v the strain.
- Bifidobacterium lactis Bb12—the genus is bifidobacterium, the species lactis and the strain Bb12.
Within each genus, there are numerous species and within each species, there are numerous strains. The strain is important because different strains within the same species may have different attributes and functions.
Probiotic Supplements
A probiotic supplement may include one or many species and strains, that meet the above criteria. They may even include yeasts such as the beneficial yeast Saccharomyces boulardii.
Niche markets such as irritable bowel syndrome sufferers or infant health are often the focus for the marketing of a probiotic supplement. However, the majority of probiotic supplements are for general intestinal health and contain a mixture of probiotic bacteria from different genera, species and strains.
Evidence suggests that a probiotic supplement should contain many strains, as the intestinal environment is very complex and a single strain probiotic supplement may be less effective, according to Bengmark S. et al from the article 'Prebiotics and Synbiotics in Clinical Practice' (2005), published in the journal Nutrition in Clinical Practice.
Summary
Our gut contains a vast number of bacteria, most of which have not been identified due to culturing difficulties. Newer research using gene technology can now identify the bacteria within the intestinal flora composition with more accuracy; however, the full diversity and complexity of the intestinal bacteria within the intestinal tract may never be known.
A probiotic supplement is a safe and well tolerated way to maintain a healthy intestinal flora, providing a daily dose of beneficial bacteria. If flatulence or bloating occurs, reduce the dose of the probiotic until symptoms abate then gradually increase dose.
For further interest visit USProbiotics
References:
Braun, L., & Cohen, M. (2007). Herbs & Natural Supplements- An evidence- based guide (2nd ed.). Marrickville: Elsevier
Delcenserie, V., Martel, D., Lamoureux, M., Amiot, J., Boutin, Y., & Roy, D. (2008). Immunomodulatory effects of probiotics in the intestinal tract. Curr Issues Mol Biol, 10(1-2), 37-54.
Douglas, L. C., & Sanders, M. E. (2008). Probiotics and prebiotics in dietetics practice. J Am Diet Assoc, 108(3), 510-521.
O'Hara, A. M., & Shanahan, F. (2006). The gut flora as a forgotten organ. EMBO Rep, 7(7), 688-693.
Melissa Peterson - Melissa Peterson is a naturopath specializing in nutrition education. Melissa has been writing and editing technical and patient-friendly ...
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