The Absorption of Vitamins and Minerals
Almost all nutrients are absorbed in the first two sections
of the small intestine which are called the duodenum and the jejunum. With the
exception of vitamin B12, very little is absorbed in the ileum purely because
most of the nutrients have been absorbed before the food reaches this section.
Most vitamins are freely absorbed in this section without complication.
However, the absorption of minerals is more complex.
All minerals exist attached to another molecule, and therefore can be either
a salt form such as Zinc citrate or can be attached to amino acids. Absorption
problems occur when the minerals are present in a salt form. When a salt mineral
is ingested, the acid in the stomach splits the molecule into zinc and citric
acid. This means that the zinc atom is electrically charged and reactive. This
causes the zinc to stick to the wall of the intestine and can lead to irritation.
It is believed that the zinc atom then needs to bind
to amino acids from food before it can pass through the intestinal wall. This
is generally the case for most minerals, except when in amino acid chelate form.
When the minerals are already bound to amino acids, they do not dissociate as
easily in the stomach and therefore do not stick to the walls of the intestine
which allows them to be absorbed easily.
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