Living microorganisms have long been used as supplements to restore gut health at times of dysfunction. It is clear that different strains from a given microbial group may possess different properties. It is thus important to establish which specific microbial strain may have a beneficial effect on the host; even closely related strains can have significantly different or even counteracting effects. Their properties and characteristics should thus be well defined; studies using closely related strains cannot be extrapolated to support each other.
type of diarrhea being investigated, and may therefore differ between viral diarrhea, antibiotic-associated diarrhea, or traveller's diarrhea.
Viral diarrhea Shortening of the duration of rotavirus diarrhea using Lactobacillus GG (LGG) is perhaps the best-documented probiotic effect. A reduction in the duration of diarrhea was first shown in several studies around the world and also in a recent multicenter European study on the use of LGG in acute diarrhea. Other investigators demonstrated that supplementation with a combination of Bifidobacterium bifidum and Streptococcus thermo-philus reduces the incidence of diarrhea and shortens the duration of rotavirus shedding in chronically hospitalized children. On average, the duration of diarrhea was shortened by 1 day in both hospitalized children and those treated at home.
Other investigators have studied the immune modulating effects of probiotics as a means of reducing diarrhea, suggesting that the humoral immune system plays a significant role in the pro-biotics' effect.
From these numerous studies it is clear that pro-biotics do indeed play a therapeutic role in viral diarrhea. Even meta-analyses have been conducted in this area, showing that probiotic therapy shortens the duration of acute diarrhea in children. However, the exact mechanism of action involved is not clear and is very likely multifactorial.
Antibiotic-associated diarrhea The incidence of antibiotic-associated diarrhea is between 5 and 30%. The success of probiotics in reducing or preventing this form of diarrhea has been convincing, and includes a number of probiotics as well as various antibiotics.
LGG has been shown to prevent antibiotic-associated diarrhea when consumed in both yogurt form or as a freeze-dried product. Also, Saccharo-myces boulardii has been found to be effective in preventing antibiotic-associated diarrhea. Other microorganisms such as Enterococcus faecium or a combination of L. acidophilus and L. bulgaricus have also been reported to be effective.
Alleviation of symptoms of allergic disease It has been shown that changes in intestinal microflora composition precede the development of some allergic diseases, indicating a potential area for probiotic application. LGG given prenatally to mothers and during the first months to infants with a high risk of atopic disease has reduced the prevalence of atopic eczema to about half in the infants receiving the strain. Furthermore, extensively hydrolyzed whey formula supplemented with LGG or Bifidobacterium lactis Bb12 is more effective than unsupplemented formula in eczema alleviation in infants with atopic eczema.
These results indicate a high potential for probio-tic application in the treatment and reduction of risk of allergic diseases.
Lactose intolerance Several studies have shown that lactose-intolerant individuals suffer fewer symptoms if milk in the diet is replaced with fermented dairy products. The mechanisms of action of lactic acid bacteria and fermented dairy products include the following: lower lactose concentration in the fermented product due to lactose hydrolysis during fermentation; high lactase activity of bacterial preparations used in production; and increased active lactase enzyme entering the small intestine with the fermented product or within the viable bacteria.
The bacterial enzyme beta-galactosidase, which can be detected in the duodenum and terminal ileum after consumption of viable yogurt, is thought to be the major factor improving digestibility by the hydrolysis of lactose, mainly in the terminal ileum. Another factor suggested to influence lactose digestion is the slower gastric emptying of semisolid milk products such as yogurt.
In conclusion, there is good scientific evidence to demonstrate the alleviation of lactose intolerance symptoms by specific probiotic lactic acid bacteria. However, the strain-specific lactase activities may vary from nil to very high values. Thus, different products may have varying lactose contents and individual strains, when released into the duodenum, vary in their lactase activity.
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