Friendly Bacteria
by Cheryl L. Jenkins PhD
Supermarket shelves are overflowing with so called ‘friendly bacteria to aid digestion’ but what exactly are probiotics, not to mention prebiotics,
and do they really benefit your digestive health?
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Breast milk contains proteins that
promote the growth of friendly
bacteria. |
Essentially, probiotics are live-bacterial cultures, typically available in the form of fermented milks or fruit juices, which are eaten to promote digestive health. The practise of eating live bacteria has been used for centuries as a way to promote health. Probiotics usually contain Lactic Acid bacteria or Bifidobacteria that have a long-standing association with health. Prebiotics, on the other hand, are foods that contain nutrients, which are not fully digested by the body and aid the growth of your indigenous or native friendly bacteria.
A huge number of microbes live on and in the human body: on the skin, in the digestive tract between the mouth and the anus, and in the vaginal tract in women. Microbes are involved in many aspects of our life including the development of a healthy immune system, prevention of infection from harmful microbes and maintaining a healthy gut. The gastrointestinal tract is the second largest surface area in the body and the maintenance of its uniquely balanced microflora is essential to optimum health. The human gut is a very hospitable environment and bacteria are able to grow a million times faster than humans. As a result our guts contain the equivalent of one kilogram of bacteria!
Friend or Foe?
How can we tell if a bacterium is a friend or foe, and where do they come from?
In essence, friendly bacteria are those that help the body to function: potentially harmful bacteria may produce toxins or damage the body.
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| Porridge is a good source of prebiotics. |
We first acquire bacteria during birth; however, the key factor that influences the microbes that colonise our gut is whether we are breast or bottle-fed. Proteins in breast milk help to promote the growth of a friendly bacterium, known as Bifidobacteria. Within a few weeks Bifidobacteria comprise 90% of the digestive microflora of a child fed on breast milk. These friendly bacteria make a baby’s gut acidic, which creates a protective barrier that prevents infection from other potentially harmful bacteria. This is important, as the child’s own immune system is not yet fully developed. Unfortunately, the proteins provided by modified cows milk used in formula feeds do not promote the growth of Bifidobacteria and mean that a formula-fed baby may be more prone to infection from potentially harmful bacteria.
The introduction of solid foods will promote the growth of other species of bacteria that colonise different areas of the digestive tract according to its requirements for growth. This trend continues as we age, changes in diet alter the digestive environment and will subsequently influence which bacteria can thrive and those which die off.
Antibiotics can also change our digestive mircoflora. Although they are often necessary to fight infections by killing harmful bacteria they also kill some of our friendly bacteria. As the friendly bacteria die off they are no longer able to keep the disease-causing bacteria in check and so they begin to multiply and may cause illness. Taking probiotics has been suggested to help maintain more of your healthy bacteria, but do they really work?
Probiotics: Do They Work?
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Lactic acid bacteria (Lactobacillus)
are friendly bacteria. |
There is much debate among scientist as to whether the live bacteria contained in probiotics are able to survive transit through the highly acidic digestive environment in the stomach to the lower intestine, where they are most beneficial.
Scientists at the University of Reading investigated whether bacteria isolated from 11 commercially available probiotics could survive transit through a simulated digestive system. Although the study concluded that not all strains were able to survive, it was acknowledged that commercially available probiotics also contain prebiotics that may aid the survival of the bacteria into the digestive system.
There is some evidence that probiotics, such as Lactobacillus and Bifidobacteria, can reduce levels of some cancer-causing substances. Probiotics have also been linked with reducing childhood diarrhoea, which is a major cause of death in the developing world. In fact, there is increasing evidence for the beneficial effects of probiotic use among those who are ill. However, there is little evidence-based research for the benefits of commercially available probiotics when used by healthy individuals.
Prebiotics: Do They Work?
Eating prebiotics has been shown to significantly increase the number of friendly bacteria regardless of your health status. Prebiotics are found in foods that are not fully digested by the body. When these foods reach the intestines they provide nutrients that support the growth of friendly bacteria. Most of these nutrients are complex carbohydrates, such as fructo-oligosaccharides (FOS) and beta-glucans, which can be found in onions, leeks, cabbage, bananas, chicory, Jerusalem artichokes and porridge, respectively. Commercial prebiotics are also available in health food stores.
Maintaining Digestive Health
Maintaining digestive health can influence your overall health and well-being. Including foods that are prebiotics in your diet is a good way to help maintain a healthy digestive system. If you fall ill or are taking a course of antibiotics you may wish to consider starting a course of probiotics. Advice from experts at the University of Reading is to stick to the well-known brands, as these are most likely to be formulated to ensure lots of friendly bacteria reach your lower intestines where they are most needed.
Want more information? Good resources to check out
Food Standards Agency Report (G01022). 2005
Reid, R. et al. (2003). Clin Microbiol Rev. 16(4): 658-672
Gibson, G. (1998). B J Nutr. 80 suppl. 2: S209-S212
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See Also:
Bach And Bush Flowers
Health_MOT
PMS
Mentally Disabled Children
The Elixir Of Life
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