Bacteria! The word usually conjures up unwelcome images of invasive, pathogenic germs intent on wreaking havoc with one’s health. But not all bacteria are bad. Many of these microorganisms are in fact crucial to health, existing in a symbiotic and mutually beneficial relationship with the human body as host. ‘Friendly’ or ‘beneficial’ bacteria – and some yeasts – are known as probiotics and the human digestive tract normally contains about 400 types of these ‘intestinal microflora’ that reduce the growth of harmful bacteria, promote a healthy digestive system and help fight disease.
The word probiotic means ‘for life’. It derives from the Latin pro (for) and the Greek bios (life).The World Health Organization and the Food and Agricultural Organization of the United States define probiotics as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.”
Probiotic bacteria are found primarily in the small and large intestines. Conditions within the first part of the small intestine are not ideal, due to the naturally high pH that occurs there, but those in the large intestine are ideal and the number and variety of organisms there are the highest – more than one billion organisms per gram of intestine.
Background
Historically, fermented foods such as yoghurt, kefir, miso and sauerkraut have been the primary sources of dietary probiotics. The positive role that certain bacteria play in human health was first publicised by Russian scientist and Nobel laureate Eli Metchnikoff, who in the beginning of the 20th century suggested it would be possible to modify the gut flora and replace harmful microbes with useful ones. He proposed that consumption of fermented milk would “seed” the intestine with harmless lactic-acid bacteria and decrease the intestinal pH, which would suppress the growth of harmful proteolytic bacteria. He introduced sour milk fermented with the bacterium he called “Bulgarian Bacillus”.
It was later established that Bulgarian Bacillus, or Lactobacillus delbrueckii subsp. Bulgaricus, could not live in the human intestine and it was proposed that bacteria originating from the gut were more likely to produce the desired effect in this region. The two that became best known are Lactobacillus and Bifidobacterium. In 1935 certain strains of Lactobacillus acidophilus were found to be very active when implanted in the human digestive tract.
Bifidobacterium was first isolated from a breast-fed infant by Henry Tissier who worked at the Pasteur Institute. The isolated bacterium – named Bacillus bifidus communis - was later renamed to the genus Bifidobacterium. Tissier found that bifidobacteria were dominant in the gut flora of all breast-fed babies and he observed clinical benefits from treating diarrhoea in infants with bifidobacteria.
The term “probiotics” was coined in 1953 by Werner Kollath. As opposed to antibiotics, probiotics were defined as “microbially-derived factors that stimulate the growth of other microorganisms”. Probiotics were originally thought to beneficially affect the host simply by improving its intestinal microbial balance, thus inhibiting pathogens and toxin-producing bacteria. Over the past 30 years, however, science has come to a better understanding of bacteria and their potential for preventing and treating a wide range of health conditions.
As a result of increased investigation, various bacterial species with alleged beneficial health properties have been introduced and probiotics are now widely available in the form of dietary supplements – capsules, tablets and powders – as well as in a variety of foods. The science of probiotics has evolved into a rapidly growing field, generating a great deal of interest among healthcare professionals and consumers and the use of probiotics is now more widely accepted and practised than ever before.
Probiotic Health Benefits
New research is establishing how important the supplementation of probiotics can be for a variety of health conditions. Friendly bacteria are vital for proper development of the immune system, protection against disease-causing microorganisms, enhancing digestion, allergy prevention and the absorption of food and nutrients. Probiotics help prevent the overgrowth of yeast and fungus and produce substances that can lower cholesterol.
A good probiotic supplement contains billions of live bacteria to bolster and replenish levels of the health-promoting ‘good bugs’ in the digestive tract. It is theorised that approximately 80 percent of the immune system resides in the intestines and probiotics enhance the immune system by favourably altering the gut micro-ecology and preventing unfriendly organisms from gaining a foothold. This is known as “competitive inhibition”. By covering the intestinal wall, good bacteria can physically prevent bad bacteria from attaching and colonising. They also make the environment hostile by increasing acidity in the intestine – which inhibits pathogenic bacteria – and they produce bacteriocins that are toxic to pathogens and directly inhibit or antagonise them. (An example of the latter is L.acidophilus that produces hydrogen peroxide.) Furthermore, by using up the nutrients within the digestive tract the good bacteria help prevent the survival of pathogenic organisms by literally starving them.
Probiotics are widely recommended for treatment of the diploid fungus infections candida albicans (a form of yeast), because they establish large, healthy populations of friendly bacteria that compete with the candida fungus that is trying to take up residence in the intestine. Probiotics are therefore essential in the treatment and prevention of thrush, vaginal yeast infections and athlete’s foot.
Recent research on the molecular biology and genomics of Lactobacillus has focused on the interaction with the immune system, anti-cancer potential and potential as a biotherapeutic agent in cases of antibiotic-associated diarrhoea, travellers’ diarrhoea, paediatric diarrhoea, inflammatory bowel disease and irritable bowel syndrome.
Experiments looking at the benefits of probiotic therapies suggest a range of potentially beneficial medicinal uses, but for many of the potential benefits research is limited and only preliminary results are available. It is important to be aware that effects described for one strain are not general effects of probiotics and effects found from one species or strain of probiotics do not necessarily hold true for others, or even for different preparations of the same species or strain.
Only certain strains of bacteria or yeast have been shown to work in the digestive tract and it still needs to be proved which probiotics (alone or in combination) work best to treat which diseases. It is important to be aware that each person’s mix of bacteria varies. Interactions between a person and the microorganisms in their body – and among the microorganisms themselves – can be crucial to the person’s health and wellbeing.
Disrupting Probiotic Balance
A healthy large intestine/colon should contain at least 85 percent friendly bacteria to prevent the over-colonisation of disease-causing microorganisms such as E. coli and salmonella. The colon can maintain its health with 15 percent unfriendly bacteria if the body contains at least 85 percent probiotic, friendly bacteria. However, this situation is reversed in most people. The ratio between good and other bacteria is one of the critical factors determining optimal health. Many lifestyle and environmental factors can adversely affect this delicate balance within the digestive tract, greatly reducing the number of friendly bacteria and thereby allowing pathogenic bacteria to take hold.
The resulting imbalance is known as dysbiosis and can be caused by bacterial, fungal and parasitic infections, stress, travelling, antibiotic treatment, alcohol, poor diet, pharmaceutical medications, inadequate dietary fibre, environmental toxins and infant formula feeding. Dysbiosis normally presents as a combination of digestive disturbances such as excessive flatulence, abdominal bloating, constipation and/or diarrhoea and colic in infants. If left untreated it can contribute to leaky gut syndrome, compromise the immune system and increase susceptibility to infections, allergies and inflammatory disorders.
Prebiotics
These are also thought to improve the balance of probiotics in the intestines. They are non-digestible carbohydrates that stimulate the growth and activity of beneficial microorganisms. Sources of prebiotics include fructo-oligosaccharides (FOS) and inulin, found in onions, asparagus, chicory and banana. FOS is also available as a supplement and is sometimes combined with probiotic dietary supplements. When probiotics and prebiotics are combined they form a synbiotic.
NCCAM Research
In November 2005 the topic of probiotics was explored during a conference in the United States that was co-funded by the National Centre for Complementary and Alternative Medicine (NCCAM) and convened by the American Society for Microbiology. According to the conference report, some uses of probiotics for which there is encouraging evidence from the study of specific probiotic formulations are as follows:
- To treat diarrhoea (this is the strongest area of evidence, especially for diarrhoea from rotavirus)
- To prevent and treat infections of the urinary tract or female genital tract
- To treat irritable bowel syndrome
- To reduce recurrence of bladder cancer
- To shorten how long an intestinal infection lasts that is caused by the bacterium Clostridium difficile
- To prevent and treat pouchitis (a condition that can follow surgery to remove the colon)
- To prevent and manage atopic dermatitis (eczema) in children
The conference panel also noted that in studies of probiotics as cures, any beneficial effect was usually low; a strong placebo effect often occurs; and more research (especially in the form of large, carefully designed clinical trials) is needed in order to draw firmer conclusions.
Side-Effects and Risks
Probiotic bacteria are already part of the normal digestive system and are usually considered safe, but safety has not been thoroughly studied scientifically. More scientific knowledge is needed about probiotics, including their appropriate use and safety, specifically for young children, the elderly and people with compromised immune systems. Possible side-effects may include mild, temporary digestive complaints such as gas and bloating. People who are immunosuppressed should seek medical advice before using probiotics as they may interact with immunosuppresant medication.
When using dietary supplements, keep in mind the following:
- Always inform your doctor or healthcare providers about any CAM practices you use. Tell them if you are using a dietary supplement or if you are thinking about combining a dietary supplement with your conventional medical treatment. It may not be safe to forgo conventional medical treatment and rely only on a dietary supplement. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care and is especially important for women who are pregnant or breastfeeding.
- Dietary supplements may not be standardised in their manufacturing. This means that how well they work may differ among brands. The form you buy in health-food or grocery stores may not be the same as the form used in research.
Suzanne Ellis
Brought to you by HPA.
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