Intestinal microecology and cancer A number of studies have focused on the impact of probiotics on intestinal microecology and cancer. Lactobacillus acidophilus, L. casei Shirota strain, and LGG have been shown to have inhibitory effects on chemically induced tumors in animals. Some specific strains of probiotic bacteria are able to bind carcinogens and to downregulate some microbial carcinogenic enzymatic activities. This phenomenon may then reduce carcinogen production and exert a beneficial effect in the colon, the urinary tract, and the bladder.
The most interesting documentation is that concerning L. casei Shirota. There have been several mechanistic studies on the effects of the strain reporting decreased mutagen excretion, and some human clinical studies have been conducted using this strain. In clinical and multicenter studies carried out in Japan, prophylactic effects of oral administration of L. casei Shirota on the recurrence of superficial bladder cancer have been reported. Recently, a large Japanese case control study has been conducted on the habitual intake of lactic acid bacteria and risk reduction of bladder cancer. Results suggested that the habitual intake of fermented milk with the strain reduces the risk of bladder cancer in the Japanese population. More studies, and especially human studies in other countries, are needed prior to the establishment of firm conclusions.
Irritable bowel syndrome There is a rationale for investigating the effect of probiotics in the treatment of this common disorder where intestinal motility and dysfunctions in the intestinal microflora are important factors to consider. In a recent study using L. plantarum 299v, a reduction of symptoms was reported. Enterococcus faecium preparations have also been evaluated for the treatment of patients with irritable bowel syndrome, and although patient-recorded symptoms did not show significant differences, the physician's subjective clinical evaluation revealed an improvement.
Inflammatory bowel disease Inflammatory bowel disease (IBD) comprises a heterogeneous group of diseases of unknown etiology (Crohn's, ulcerative colitis, and pouchitis), but here also factors related to the intestinal microflora seem to be involved, providing a rationale for the application of probio-tics. From reviewing studies on the use of probiotics in IBD it can be concluded that, although there are some promising preliminary findings, more well-planned long-term studies are needed before any firm conclusions can be drawn.
Traveller's diarrhea There are a few studies on the prevention of traveller's diarrhea using probiotics and these show a positive outcome for LGG and a combination of L. acidophilus LA5 with B. lactis Bb-12. The results offer some indication of beneficial effects, even though some studies yielded no reported effects, but information from good and extensive human studies using defined strains for traveller's diarrhea is still largely lacking. The current data on traveller's diarrhea show no scientifically proven effects for any of the strains used. More studies are required for efficacy assessment.
Helicobacter pylori eradication Specific strains of lactic acid bacteria have been reported to inhibit a wide range of intestinal pathogens including Helicobacter pylori, which is involved in the process of gastric ulcer development. Lactic acid bacteria are often able to survive acidic gastric conditions and it has therefore been proposed that they may have a beneficial influence during the eradication of H. pylori. It has been reported that both the inhibitory substances produced and the specific strains may influence the survival of Helicobacter, and studies have been conducted, particularly with a L. johnso-nii strain. It has been shown that there is good in vitro inhibition and that fermented milk containing the strain has a positive effect when consumed during Helicobacter eradication therapy. However, more controlled human studies in different populations need be conducted to verify this effect.
Cholesterol control The cholesterol-lowering effects of probiotics have been the subject of two recent reviews with contradictory results. The first, which focused on short-term intervention studies with one yogurt type, reported a 4% decrease in total cholesterol and a 5% decrease in LDL. Contrary to this, the second review concluded that no proven effects could be found. In this context, it is clear that long-term studies are required before the establishment of any conclusion.
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