No abstract

A human trial was carried out to assess the ileal and fecal survival of Lactobacillus casei DN-114 001 ingested in fermented milk. Survival rates were up to 51.2% in the ileum and 28.4% in the feces. The probiotic bacterium has the capacity to survive during its transit through the human gut.

The composition and activities of the faecal microbiota in twelve healthy subjects analysed in a single open study were monitored before (1-week baseline step), during (10 d supplementation step) and after (10 d follow-up step) the ingestion of a fermented milk containing Lactobacillus casei DN-114 001. Fluorescent in situ hybridisation with group-specific DNA probes, real-time PCR using L. paracasei group-specific primers and temporal temperature gradient gel electrophoresis (TTGE) using group-specific primers were carried out, together with bacterial enzyme activity and metabolite analyses to monitor the structure and activities of the faecal microbiota. L. casei DNA was detected in the faeces of all of the subjects by TTGE after 10 d supplementation. Its quantification by real-time PCR showed a 1000-fold increase during the test step compared with initial levels. No major modification in either the dominant members of the faecal microbiota or their activities was observed during the trial. In conclusion, the short-term consumption of a milk product containing L. casei DN-114 001 was accompanied by a high, transient increase in the quantity of this strain in the faeces of all of the subjects without markedly affecting biochemical or bacteriological factors.

This document addresses nutritional and functional changes brought about by heat treatment of yogurt containing live cultures. Several lines of research evidence suggest that these products are not equivalent. Recent research shows that yogurt bacteria are able to survive passage through the human intestine. Yogurt containing viable starter cultures has been shown to improve lactose digestion in lactose-intolerant people; heat treatment of the product diminishes this improvement. There are indications for a role of live yogurt cultures in modulating the immune system of the consumer. Long-term consumption of live yogurt reduces nasal allergies, particularly in young adults, a reduction that is not observed any more after heat treatment. Studies in the growing pig, an accepted model for studying protein digestion in humans, show that nitrogen absorption from live yogurt is higher and more evenly distributed in time than nitrogen absorption from heat-treated fermented milk. Taken together, these findings indicate that heat treatment of yogurt results in relevant nutritional and functional changes which would challenge an assertion of their equivalency. Such differences should be reflected in naming of these products to avoid consumer confusion. Additional health benefits of yogurt include the release of bioactive peptides, impact on gut flora, alleviation of diarrhoea in children, immune system modulation, prevention of infections, inhibition of mutagenesis and carcinogenesis, improved oral health and improved symptoms of collagen-induced arthritis. These effects have not been tested and documented for heat-treated fermented milk.