The diverse strains of microorganisms within the human digestive tract form an internal ecosystem that has profound effects on human health and well being. When that ecosystem is in balance, we thrive – when it is unbalanced, we invite and experience discomfort or disease. Scientists and physicians call this ecosystem our microbiota, but we know those beneficial organisms within our microbiota that promote internal ecological balance better as probiotics.
Probiotics (and prebiotics) help us in many ways - so much so, that they should be considered an essential food group. Probiotics compete successfully with pathogenic or potentially harmful bacteria within our digestive tract, lowering their populations sufficiently so we find we are less vulnerable to digestive disorders and disease. Probiotics also play a vital role in the human body by regulating immune and inflammatory responses, producing vitamins and enzymes, scavenging non-digested food components and human body metabolites, and feeding the intestinal lining .
Recent breakthroughs in research in the unified fields of immunology, microbiology, nutrition and physiology indicate the vital role of probiotics within our body. Some of the conditions scientists and physicians are now beginning to recognise that may either be prevented, helped, or even cured by probiotics include: diarrhoea, inflammatory bowel disease, irritable bowel syndrome, allergies, asthma, eczema, multiple sclerosis, yeast infections, the eighty plus recognised autoimmune disorders, cardiovascular disease, obesity, colorectal cancer, fibromyalgia, chronic fatigue syndrome, autism, leaky gut syndrome, upper digestive tract ulcers (through competitive advantage over Helicobacter pylori) and colitis. It is important to add, however, that probiotics should never be used as the sole means of treating serious medical conditions. Diet, lifestyle, and state of mind are also important, as are conventional and complimentary medical and therapeutic approaches.
Prebiotics are foods which provide a competitive advantage within our internal ecosystem for probiotics. The best known source of prebiotics is dietary fibre – we can’t digest it, but many probiotic microorganisms thrive on it. Some prebiotic foods favour probiotics; others disadvantage the microorganisms they compete against; while others act like selective antibiotics, inhibiting the growth of unfavourable microorganisms (e.g. phenols like tannins, phytoestrogens, flavonoids, flavonols, bioflavonoids). When seeking out prebiotics, consume fibre foods for their soluble fibre content (e.g. oats, barley, rice bran, psyllium husk, berries, legumes, and unpeeled fruits and vegetables) because this confers a twofold advantage: probiotic bacteria thrive on soluble fibre, and as they consume it, they release short chain fatty acids (not fats, but vinegar-like acids) that inhibit the growth of non-probiotic organisms, such as Escherichia coli (E. Coli). Good examples of prebiotics include: fruit and vegetables with the skin on; whole grains, nuts and seeds; dark unsweetened berry juices; herbs and spices (especially oregano); wholegrain sourdough bread; oats; legumes; green tea; and dark chocolate (or raw cacao). Foods to specifically avoid at all costs are the refined carbohydrates – most especially white bread and white sugar. Standard wheat is also good to avoid, even in wholegrain form - try other grains, such as whole spelt or whole rye. In moderation, red wine and dark ales and stouts are also sources of prebiotics.
Our bodies are host to on average one hundred trillion microorganisms at any one time, and over 99% of these are bacteria, and about 80% of these inhabit our digestive tract. Some bacteria are always helpful to us (e.g. species of Lactobacillus and Bifidobacterium), while others are never helpful, and may cause disease if their numbers rise too high (e.g. Clostridium difficile and Pseudomonas aeruginosa). Outnumbering these, however, are bacteria that may be beneficial or detrimental to our health, depending on their population size and location within the body (e.g. species of Bacteroides and Klebsiella). Bacteria are self-replicating single-celled life-forms, and their rate of replication can be rapid indeed: E. Coli, for example, can double their population size in as little as 20 minutes if conditions are optimal.
The most common yeast of the human microbiota is Candida albicans. If kept in check by competition with probiotic organisms, it is harmless, but if it is allowed to attain a sizeable population, then it can be responsible for various illnesses, such as diarrhoea and thrush. Probiotic yeasts confer benefits, despite their relatively low occurrence within us. Saccharomyces boulardii, for example, has been shown to be effective in the control of Clostridium difficile related diarrhoea.
A third principle also exists, that of “metabiotics”. Fermented foods or beverages in which the probiotic complement is no longer living still convey health benefits through the actions of their metabolites – enzymes and other compounds (e.g. short chain fatty acids) formed during the fermentation process.
Huffnagle, Gary B. (Ph.D.) and Wernick, Sarah (2007) The Probiotics Revolution. New York, Bantam Dell.
Alexander (M.D.) (2013) The Complete Guide to Understanding Probiotics
and Prebiotics. Accessed online 5th December 2013,