Assessment of the Benefits of Live Yogurt: Methods and Markers for in vivo Studies of the Physiological Effects of Yogurt Cultures

Abstract

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.