Probiotics are defined as “live micro-organisms that when administered in adequate amounts confer a health benefit on the host” (World Health Organisation, 2001). Probiotics are traditionally used to restore the balance of the intestinal microflora which can become unbalanced due to illness, stress, age, travelling, or the use of medication such as antibiotics. It is important to note that the effects are strain specific and cannot be regarded as general for the various probiotics.
Most probiotic organisms belong to the lactobacillus and bifidobacteria genera. However, there are many genera, species, and strains of bacteria that inhabit the intestinal flora of the human gastrointestinal tract at any one time. It is estimated the human gut contains more than 100 trillion bacterial cells from over 40,000 different species. It should be noted that “probiotic” bacteria are considered only those that have documented effects.
Clinical studies have demonstrated that probiotics can offer many health benefits. Some of the scientifically established health effects are:
- Reduction in the occurrence and duration of rotavirus diarrhoea.
- Reduction in duration of antibiotic-associated diarrhoea.
- Alleviation of symptoms of lactose intolerance.
- Alleviation of symptoms of food and skin allergies in children.
- Reduction of recurrent ear and bladder infections.
- Reducing incidence and/or duration of bacterial vaginosis.
- Improvement in mucosal tolerance.
- Improvement of halitosis.
Probiotic bacteria are very strain dependent, not species dependent. A strain is a type of a bacterial species, similar as to the example below:
- Bacterial group = German car = lactic acid bacteria
- Bacterial genus = Volkswagen = Lactobacillus
- Bacterial species = VW Golf = Lactobacillus acidophilus
- Bacterial strain = VW Golf 1.4 D = Lb. acidophilus LC1
Everybody knows that a Volkswagen Golf 1.4 D has other characteristics than a Volkswagen Golf 2.0i turbo, but you can’t see the difference on the outside.
The same is true for bacteria; they all look the same, but the biological characteristics (‘the engine’) are different. Hence, claims on health effects of a certain probiotic are only valid for that specific strain, not species.