ВУЗ:
Составители:
Рубрика:
radical. Dehydro-ascorbate is recycled back to ascorbic acid by
the enzyme dehydro-ascorbate reductase. Thus, dehydro-
ascorbate is found in only very low levels compared with
ascorbate. As a scavenger of ROS ascorbate has been shown to
be effective against the superoxide radical anion, H
2
O
2
, the
hydroxyl radical, and singlet oxygen. In aqueous solutions
vitamin C also scavenges reactive nitrogen oxide species
efficiently, preventing the nitrosation of target molecules. The
major sources of ascorbate in the diet are fruits, especially citrus
fruits, kiwi fruit, cherries and melons, and vegetables such as
tomatoes, leafy greens, broccoli, cauliflower, Brussels sprouts,
and cabbage; its content might exceed lOOmg ascorbate/100 g
fresh weight. At low dose levels (100 mg) the bioavailability
values for vitamin C from synthetic and food sources are very
similar the efficacy of absorption decreases with increasing dose
levels. There is evidence from studies in vitro that vitamin C is
capable of regenerating tocopherol from the tocopheroxyl
radical which is formed on inhibition of lipid peroxidation by
vitamin E. (2300)
22. Prebiotics and synbiotics: concepts and
nutritional properties
The main role of diet is to provide enough nutrients to meet the
requirements of a balanced diet, while giving the consumer a
feeling of satisfaction and well-being. The most recent
knowledge in bioscience supports the hypothesis that diet also
controls and modulates various functions in the body, so as to
contribute to the maintenance of a state of good health and
reduce the risk of some diseases. It is such an hypothesis which
is at the origin both of the concept of “functional food” and the
development of a new discipline of the 'functional food science.
A” functional food” is a food which contains (in adequate
proportion) one or a combination of components which
functions in the body so as to have positive cellular or
physiological effects' (Roberfroid, 1996). Research and
development of 'functional food' is part of the science of
nutrition and the benefit associated with its intake has to be in
the context of the diet.
The strategy for research and development of a 'functional food'
requires:
(1) the demonstration of an interaction with (a) function(s) in
the body;
(2) some understanding of the mechanism thereof;
(3) the establishment of the effect in relevant biological
systems;
(4) the formulation of sound hypotheses;
(5) the testing of these hypotheses in human nutrition studies.
The concepts of prebiotics and synbiotics
In the context of this paper the potential 'functional foods' to be
discussed are the prebiotics and the synbiotics. A prebiotic is
defined as a nondigestible food ingredient that beneficially
affects the host by selectively stimulating the growth and/or
activity of one or a limited number of bacteria in the colon. It is
a substance which modifies the composition of the colonic
microflora in such a way that a few of the potentially health-
promoting bacteria (especially lacto-bacilli and bifidobacteria)
become predominant in numbers. A synbiotic is the product in
which both a probiotic and a prebiotic are combined in a single
product. It is defined as a mixture of a probiotic and a prebiotic
that beneficially affects the host by improving the survival and
the implantation of live microbial dietary supplements in the
gastrointestinal tract, by selectively stimulating the growth
and/or by activating the metabolism of one or a limited number
of health-promoting bacteria'. The prebiotics developed so far
are the non-digestible oligosaccharides and especially the non-
radical. Dehydro-ascorbate is recycled back to ascorbic acid by A” functional food” is a food which contains (in adequate
the enzyme dehydro-ascorbate reductase. Thus, dehydro- proportion) one or a combination of components which
ascorbate is found in only very low levels compared with functions in the body so as to have positive cellular or
ascorbate. As a scavenger of ROS ascorbate has been shown to physiological effects' (Roberfroid, 1996). Research and
be effective against the superoxide radical anion, H2O2, the development of 'functional food' is part of the science of
hydroxyl radical, and singlet oxygen. In aqueous solutions nutrition and the benefit associated with its intake has to be in
vitamin C also scavenges reactive nitrogen oxide species the context of the diet.
efficiently, preventing the nitrosation of target molecules. The The strategy for research and development of a 'functional food'
major sources of ascorbate in the diet are fruits, especially citrus requires:
fruits, kiwi fruit, cherries and melons, and vegetables such as (1) the demonstration of an interaction with (a) function(s) in
tomatoes, leafy greens, broccoli, cauliflower, Brussels sprouts, the body;
and cabbage; its content might exceed lOOmg ascorbate/100 g (2) some understanding of the mechanism thereof;
fresh weight. At low dose levels (100 mg) the bioavailability (3) the establishment of the effect in relevant biological
values for vitamin C from synthetic and food sources are very systems;
similar the efficacy of absorption decreases with increasing dose (4) the formulation of sound hypotheses;
levels. There is evidence from studies in vitro that vitamin C is (5) the testing of these hypotheses in human nutrition studies.
capable of regenerating tocopherol from the tocopheroxyl The concepts of prebiotics and synbiotics
radical which is formed on inhibition of lipid peroxidation by In the context of this paper the potential 'functional foods' to be
vitamin E. (2300) discussed are the prebiotics and the synbiotics. A prebiotic is
defined as a nondigestible food ingredient that beneficially
affects the host by selectively stimulating the growth and/or
22. Prebiotics and synbiotics: concepts and activity of one or a limited number of bacteria in the colon. It is
a substance which modifies the composition of the colonic
nutritional properties
microflora in such a way that a few of the potentially health-
promoting bacteria (especially lacto-bacilli and bifidobacteria)
The main role of diet is to provide enough nutrients to meet the
become predominant in numbers. A synbiotic is the product in
requirements of a balanced diet, while giving the consumer a
which both a probiotic and a prebiotic are combined in a single
feeling of satisfaction and well-being. The most recent
product. It is defined as a mixture of a probiotic and a prebiotic
knowledge in bioscience supports the hypothesis that diet also
that beneficially affects the host by improving the survival and
controls and modulates various functions in the body, so as to
the implantation of live microbial dietary supplements in the
contribute to the maintenance of a state of good health and
gastrointestinal tract, by selectively stimulating the growth
reduce the risk of some diseases. It is such an hypothesis which
and/or by activating the metabolism of one or a limited number
is at the origin both of the concept of “functional food” and the
of health-promoting bacteria'. The prebiotics developed so far
development of a new discipline of the 'functional food science.
are the non-digestible oligosaccharides and especially the non-
