Abstract
| Lactic acid bacteria (lab), used in the production of fermented dairy products, have
been reported to have a positive effect on immune system function. In this study
cow milk and soy milk yogurt prepared with commercial yogurt starter cultures
combining Lactobacillus delbrueckii sub sp. bulgaricus, Streptococcus salivarius
sub sp. thermophilus, Bifidobacterium bifidum, and Lactobacillus acidophilus were
mixed with nutritionally balanced powdered diet and fed to male Sprague-Dawley
rats. The rats were injected weekly with 1,2-dimethylhydrazine (DMH), a known
colon carcinogen. Both experimental groups contained 7 animals. In addition, there
was a biological reference group (n=7) that received no yogurt and no DMH and a
control group (n=7) that received DMH, but no yogurt. Food intake and food
spillage were recorded daily. Body weight was recorded weekly. Fecal enumeration
of lactic acid bacteria was completed at -3, +5 and +11 weeks. Colon tumor number
was measured at +11 weeks. The above procedures allowed us to assess if
immune protection, after carcinogenic challenge, was provided by LAB supplementation
in yogurt made from various milk sources. At the end of the study,
aberrant crypts in the distal 10 cm of the colon were 48.58±10.37 for the control
group, 41.27±7.13 for the soy group, 40.96±8.73 for the cow group, and 0 for the
reference group. There were no significant (p<0.05) differences among DMH-treated
groups. However, a trend was observed toward a probiotic effect of LAB in
preventing colon carcinogenesis. The dosage of DMH used in this study was on the
high end of the literature values and using less DMH may allow for more sensitive
detection of LAB effects. |
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