Factors Influencing Nutrient Availability

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The following sections will illustrate the different stages at which nutrient bioavailability
can be influenced:
a) Effects of food matrix and chemical form of nutrients
The first step in making a nutrient bioavailable is to liberate it from the food matrix and
turn it into a chemical form that can bind to and enter the gut cells or pass between
them. Collectively this is referred to as bio accessibility. Nutrients are rendered bio
accessible by the processes of chewing (mastication) and initial enzymatic digestion of
the food in the mouth, mixing with acid and further enzymes in the gastric juice upon
swallowing, and finally release into the small intestine, the major site of nutrient
absorption. Here, yet more enzymes, supplied by the pancreatic juice, continue
breaking down the food matrix.
b) Enhancers of nutrient bioavailability
Nutrients can interact with one another or with other dietary components at the site of
absorption, resulting in either a change in bioavailability or if enhancers and inhibitors
cancel each other out. Enhancers can act in different ways such as keeping a nutrient
soluble or protecting it from interaction with inhibitors.
c) Impact of inhibitors on nutrient bioavailability
Inhibitors may reduce nutrient bioavailability by: binding the nutrient in question in a
form that is not recognized by the uptake systems on the surface of intestinal cells,
rendering the nutrient insoluble and thus unavailable for absorption, or competing for
the same uptake system. Phytic acid is highly abundant in certain plant foods
d) Host factors
Internal or host-related factors can be subdivided into gastrointestinal and systemic
factors. The role of gastrointestinal factors is illustrated by the absorptive pathway of
vitamin B12. This vitamin requires gastric acid to be released from the food matrix and
then it undergoes a sequence of binding to R protein, release from R protein, binding to
the protein “intrinsic factor” (IF) and finally absorption of the intact IF-vitamin
B12 complex in the lower intestine.
e) Impact on nutrient recommendations
For several nutrients – primarily calcium, magnesium, iron, zinc, folate and vitamin A –
knowledge of their bioavailability is needed to translate physiological requirements into
actual dietary requirements.

Titany answered the question on November 5, 2021 at 05:51

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