193
Chapter 16
intestinal Bacteria
and Probiotics
introduction
Since the discovery of food fermentation, our ancestors recognized that the process yielded products that had not only better shelf life and desirable qualities but also some health benefits, especially to combat some intestinal ailments. The belief in the health benefits of fermented foods
continued throughout civilization and, even today, remains of interest among many consumers
and researchers. 1 There are differences between early beliefs and the current interest: Whereas the
early beliefs probably emerged from associated effects (getting a benefit from consuming) without
knowing the scientific basis, current interest is based on understanding the microbiology and biochemistry of fermented foods, the microbial ecology of the human gastrointestinal (GI) tract, and
the roles of some bacteria in the GI tract and in fermented foods in human health. Researchers,
however, are divided in their opinions. Some advocate the different health benefits that consumers
can have from consuming fermented foods, especially fermented dairy products, but others doubt
those attributes, especially when “cure-all” claims are made by overzealous individuals with no or
very little scientific background in the area.
In Western countries, the beneficial role of fermented milk (yogurt) in the prolongation of life
was first advocated by Metchnikoff in 1907. He suggested that the bacteria and their metabolites
in yogurt neutralized the harmful products yielded from foods in the GI tract and provided protection to human health. However, later studies produced controversial results.
In recent years, especially since the 1970s, consumers in many developed countries have been
particularly interested in the health benefits of foods. There is an increased interest in foods that
are not harshly processed and preserved, but are natural, and fermented foods are considered natural and healthy. Consumers’ interest in and demand for fermented foods have resulted in a large
production increase of many products that had very small markets before. Many ethnic products
have earned commercial status. In addition, consumers’ interest in the health benefits of some
bacterial species has stimulated production of new products containing live cells of these bacteria.
These products are generally designated as probiotics. The term has been used loosely for a while,
Chapter 16
intestinal Bacteria
and Probiotics
introduction
Since the discovery of food fermentation, our ancestors recognized that the process yielded products that had not only better shelf life and desirable qualities but also some health benefits, especially to combat some intestinal ailments. The belief in the health benefits of fermented foods
continued throughout civilization and, even today, remains of interest among many consumers
and researchers. 1 There are differences between early beliefs and the current interest: Whereas the
early beliefs probably emerged from associated effects (getting a benefit from consuming) without
knowing the scientific basis, current interest is based on understanding the microbiology and biochemistry of fermented foods, the microbial ecology of the human gastrointestinal (GI) tract, and
the roles of some bacteria in the GI tract and in fermented foods in human health. Researchers,
however, are divided in their opinions. Some advocate the different health benefits that consumers
can have from consuming fermented foods, especially fermented dairy products, but others doubt
those attributes, especially when “cure-all” claims are made by overzealous individuals with no or
very little scientific background in the area.
In Western countries, the beneficial role of fermented milk (yogurt) in the prolongation of life
was first advocated by Metchnikoff in 1907. He suggested that the bacteria and their metabolites
in yogurt neutralized the harmful products yielded from foods in the GI tract and provided protection to human health. However, later studies produced controversial results.
In recent years, especially since the 1970s, consumers in many developed countries have been
particularly interested in the health benefits of foods. There is an increased interest in foods that
are not harshly processed and preserved, but are natural, and fermented foods are considered natural and healthy. Consumers’ interest in and demand for fermented foods have resulted in a large
production increase of many products that had very small markets before. Many ethnic products
have earned commercial status. In addition, consumers’ interest in the health benefits of some
bacterial species has stimulated production of new products containing live cells of these bacteria.
These products are generally designated as probiotics. The term has been used loosely for a while,