Updated 06 September 2013

Good bacteria vs. bad bacteria

Not all bacteria are bad. In fact, some are rather good for you. But the line could be a thin one. So, what should you know?


The human body plays host to a number of micro-organisms, most of which are our friends. This is nothing to be grossed out about. In fact, the phenomenon of living in close physical association with other organisms ("symbiosis") is as common as life itself.

The bacteria that live in the colon
The colon has the largest microbial community in the body. In this part of the body, the bacterial population usually doubles once or twice a day. Many of these bacteria are, of course, also excreted during the course of the day, so that a delicate balance is maintained.

Under normal circumstances, the microbial community in the colon – which includes more than 500 different species of micro-organisms – regulates itself. Competition between the different micro-organisms, and also between the micro-organisms and their human host, serve to maintain this status quo.

These micro-organisms normally prevent infection and proliferation of "bad" bacteria (pathogens like Salmonella and Clostridia, for instance) and have a positive effect on nutrition.

However, the intestinal environment of the colon can very easily be disturbed. This may change the delicate balance of normal micro-organisms in the colon greatly. Research shows that several factors, like stress, altitude changes, starvation, parasitic organisms, diarrhoea and use of antibiotics could contribute to such a disruption.

Boosting the "good" bacteria
When the balance of microbiota is disturbed, one can become susceptible to disease. In these circumstances, boosting the numbers of "good" bacteria or yeasts present in the gastrointestinal tract can be particularly useful. This is where probiotics come into play.

Probiotics are microbial foods (e.g. yoghurt with live AB cultures) or supplements (e.g. chew tablets or capsules) that can be used to change or improve the intestinal bacterial balance to boost the health of the host. Probiotics are also available in suppositories and creams.

The most common forms of probiotics include Lactobacillus and bifidobacteria. One of the ways in which these good guys thwart the overgrowth of toxic bacteria is by competing for attachment sites and nutrients in the gastrointestinal tract. Probiotics also produce organic acids that reduce the intestinal pH and retard the growth of "bad", acid-sensitive bacteria. To really be effective, the probiotics must be able to survive the presence of bile and acid in the gastrointestinal tract.

Currently, good, scientific research studies show that certain probiotics (specifically Lactobacillus rhamnosus GG and Saccharomyces boulardii) may be particularly useful in the treatment of acute infectious diarrhoea. Strong evidence also exists for the treatment of atopic eczema in babies and children (this is an inflammatory condition of the skin that often precedes asthma and allergies), and antibiotic-associated diarrhoea.

Fermented dairy products, like live culture yoghurts, kefir (a milk drink flavoured with salt or spices) and commercial probiotic preparations, contain Lactobacillus, bifidobacteria, and other forms of probiotics.

Other forms of fermented foods, such as sauerkraut (white cabbage cut finely, salted and fermented in its own liquid), miso (a thick paste made from fermented and processed soy beans) and tempeh (a dish made from split soybeans and water) may also be cultured with Lactobacillus strains.

However, the potency and number of live organisms in commercial products may vary greatly. And many manufacturers are finding it difficult to overcome technical problems, especially in terms of keeping the micro-organisms alive under unfriendly conditions.

In addition, the US National Center for Complementary and Alternative Medicine (NCCAM) maintains that “strong scientific evidence to support specific uses of probiotics for most conditions is lacking”.

So, if you’re considering taking a probiotic supplement, it’s best to talk to your doctor first. Although these supplements generally have few side effects, it might not be useful in terms of treating your particular condition.

Take note of prebiotics too
When it comes to intestinal health, one also needs to consider prebiotica – non-digestible food products that stimulate the growth of "good" bacteria already present in the colon.

Prebiotics include foods that contain substrates, like dietary fibre and fructo-oligosaccharides, which nourish the beneficial microorganisms in the gut.

It’s therefore also important to include enough fibre in your diet by eating fruit, vegetables and whole-grains (these foods have many other health benefits, too). Food sources of the fructo-oligosaccharides include onion, asparagus, rye, banana and oats.

– (Carine Visagie, Health24)


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