This report reviews mechanisms of cancer causation and prevention in the stomach, esophagus and large bowel. Typical risk factors for gastric cancer are the presence of the bacterium Helicobacter pylori and a customary intake of salted pickled foods, that contain specific carcinogens, including 2-chloro-4-methylthiobutanoic acid and others as yet unknown. Cancer of the esophagus in the Orient has similar risk factors as salted pickled foods, but with distinct substrates. The specific carcinogensproduced under those conditions have not yet been identified. Prevention involves lower intake of salted pickled foods and regular consumption of protective vegetables, fruits and tea. Salt acts as an enhancing factor. The etiologic elements associated with proximal colon cancer are not known. For distal colon cancer, the carcinogens may be heterocyclic amines formed during frying, broiling, or cooking of meats or fish.Powerful potentiation occurs as a function of type and amount of dietary fat, generating bile acids acting as promoters in intestinal cancer development through specific mechanisms. Rectal cancer may have similar mechanisms, and in addition alcohol is a risk factor, possibly through generation of acetaldehyde. Intake of insoluble and soluble fibers is protective through increasing stool bulk, and modifying structure of bacterial flora and luminal compounds. Selective alteration of intestinal flora with bifidobacteria reduces colon cancer development appreciably. Vegetables, fruits and tea provide various inhibiting elements reducing risk of distal colon and rectal cancer.Prevention of all types of gastrointestinal cancer is possible through known mechanisms based on appropriate changes in dietary habits.
The beneficial effects of probiotic bacteria have been suggested for a century, but until now mostly anecdotal evidence has been available to support these beliefs.The main emphasis has been on development of new and more effective probiotics and only recently in validation of probiotic effects in clinical studies. This review is intended to explain the Nordic and European achievements and future plans in the development of new and more effective probiotic strains. The summary includes data on assessing new and novel methodologies for strain selection, including adhesion, colonization, potential for immune effects via cytokine release, use of gastrointestinal model systems and antigenotoxic properties. Also, first results and plans for the assessment of strains and validation of novel methodologies in pilot human trials are discussed. As a conclusion, the present state of art in the projects is given with plans on future research areas and new developments.
A total of 305 strains of lactobacilli were isolated from the feces of 40 healthy adults. They were identified by phenotypic properties such as carbohydrate fermentation pattern, gas formation and growth at 15°C, as well as DNA-DNA hybridization in some strains. The strains isolated were identified as Lactobacillus salivarius, L. gasseri, L. reuteri, L. crispatus, L. paracasei, L. rhamnosus, L. plantarum, L. acidophilus group, L. fermentum and L. coryniformis. Several isolates were not identical to the known species.Of phenospecies, L. acidophilus group biovar I was the most frequently found. Subsequently, L. casei biovar II, L. salivarius biovar Ia and L. reuteri biovar IVb were found. DNA-DNA homology studies revealed that most strains identified phenotypically as L. acidophilus group biovar I were in fact L. gasseri and some strains were not identified asalready described L. acidophilus group species found in the human intestine.
The daily intake of total dietary fiber (TDF) was evaluated from data collected by the National Nutrition Survey in Japan over a period of 41 years since1947. The interrelationships between dietary fiber, other nutrient intake and the mortality from colon cancer (MCC) were determined by a simple correlation coefficient and a time-series correlation coefficient. TDF intake per capita decreased rapidly from 27.4 g in 1947 to 15.8 g in 1963, and subsequently decreased at a lesser rate to15.3 g in 1987. The interrelationship between MCC and TDF intake could be represented by two linear regression lines, with similar findings also being observed for fat, fat energy ratio and fat/TDF. MCC has increased rapidly since the daily intake of TDF dropped to less than 18 g. A time-series analysis indicates that MCC has a significantly positive maximum correlation with the intake of total fat and with the fat energy ratio after a 16-year delay. MCC was negatively correlated with TDF after a 15-27 year delay, the maximum correlation existing with a 24-year lag (r = 0.918). Fat/TDF showed the most striking correlation with MCC with a 16-year lag (r =- 0.994) among all the parameters. It is suggested that the cause of increased MCC in Japan is positively related to the increased intake of fat. In addition, the decrease in TDF intake has accelerated MCC after a delay of 24 years. The importance of fat/ TDF as a nutritional criterion for the incidence of colon cancer needs to be betterrecognized.
The role of some intestinal bacteria species on wound-healing in mice was studied by comparing male germ-free (GF) mice with their conventionalized (Cvz) and monoassociated counterparts harboring Lactobacillus reuteri (L), Bifidobacterium longum (BB), Escherichia coli (E), Bacteroides vulgatus (B) and Clostridium perfingens (C) species. An incision was made on the dorsal skin of each mouse. A tube containing a piece of sponge was then implanted subcutaneously to measure the hydroxyproline concentration in wound tissue fluid. Mice were killed on the 7th postoperative day. Mice in the Cvz, L and BB groups showed stronger break-strengths and higher concentrations of hydroxyproline than mice in the GF group. The lactic acid concentration in Cvz, L, and BB groups was much higher than that in GF, B and C groups. The amounts of SCFAs in the Cvz group was higher than those in the GF group. Concentrations of SCFAs in the L and BB groups were not significantly higher than the values in the GF group. These results showed that the wound-healing process could be enhanced by some intestinal bacteria, and that lactobacilli and bifidobacteria may play an important role in this enhancement. The data suggest that such enhanced wound-healing in mice carrying special types of bacteria was partly due to the improvement in the nutritional status of mice caused by extra lactic acid produced by bacteria.
A new depolymerized pyrodextrin (DPD) was produced by hydrolyzing pyrodextrin, a material of indigestible dextrin, with hydrochloric acid and then heating.The effects of this substance was examined in an in vitro fermentation test of human intestinal bacteria and in a continuous ingestion test on healthy subjects. The fermentability of the indigestible portion of DPD by 106 bacterial strains from the human intestine was examined in vitro. The indigestible portion of DPD was fermented by most strains of genus Bifidobacterium, apart from B. bifidum and B. animalis. The indigestible portion of DPD-II (dextrose equivalent (DE); 33.0), which resulted from advanced acid hydrolysis, was fermented more than the indigestible portion of DPD-I (DE; 23.6). The indigestible portion of these DPDs was not fermented by Clostridium peringens, C. difficile, Escherichia coli, and staphylococci. After 14 days of daily ingestion of 10 g of DPD-II by seven healthy males, the number of fecal bifidobacteria had increased significantly in comparison with the level before ingestion. However, the number of bacteroides, the predominant bacteria in the human intestine, did not change. These results suggest that DPD, a depolymerized pyrodextrin that was, hydrolyzed without much change in the branched binding, may help to increase the number of bifidobacteria in the human intestinal flora.