From the early years of emergence of nutritional science, it has
been recognized that the ingested nutrients in the diet are not
completely utilized in the body. An increasing volume of evidence
suggests that with very few exceptions, only a proportion of
the total ingested nutrients in a diet or food is available, and the
term “availability” has come into use for this proportion (Southgate
1989). The nutrients measured by chemical analysis may not
always be fully utilizable, mainly due to the indigestible cell walls,
a bulky or dense structure, a low solubility, the presence of some
compounds inhibiting the digestion, as well as components
abundantly present in plant foods such as dietary fiber, phytic
acid, and tannic acid, which may significantly reduce the absorption
and utilization of some nutrients (Rosado and others 1987).
During food processing, derivatization of nutrients and formation
of cross linkages occur, thereby making the food inaccessible for
digestion or/and metabolism. Such parts of nutrients are also “unavailable”
From the early years of emergence of nutritional science, it hasbeen recognized that the ingested nutrients in the diet are notcompletely utilized in the body. An increasing volume of evidencesuggests that with very few exceptions, only a proportion ofthe total ingested nutrients in a diet or food is available, and theterm “availability” has come into use for this proportion (Southgate1989). The nutrients measured by chemical analysis may notalways be fully utilizable, mainly due to the indigestible cell walls,a bulky or dense structure, a low solubility, the presence of somecompounds inhibiting the digestion, as well as componentsabundantly present in plant foods such as dietary fiber, phyticacid, and tannic acid, which may significantly reduce the absorptionand utilization of some nutrients (Rosado and others 1987).During food processing, derivatization of nutrients and formationof cross linkages occur, thereby making the food inaccessible fordigestion or/and metabolism. Such parts of nutrients are also “unavailable”
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