Agriculture Reference
In-Depth Information
T A B L E 2.9. Fat-Soluble Vitamins
Vitamin/Name
a
Chemical Structure
b
Function
A/retinol
Vision—health of cornea
D/calciferol
c
Bone development/
calcium and
phosphorus in blood
E/tocopherol
d
Antioxidant
K/phylloquinone
Blood clotting
a
Vitamins often have more than one name and only a more common name is given.
b
Not all hydrogen atoms are shown; unsatisfied positions are occupied by hydrogen.
c
A number of different structures form a group of compounds of similar structure and activity called vitamin D.
The specific compound shown is calciferol.
d
A number of different structures form a group of compounds of similar structure and activity called vitamin E.
The specific compound shown is a-tocopherol.
While vitamins are essential to the proper functioning of the body, they can become
toxic in high concentrations. For the water-soluble vitamins this is not much of a problem
as excess vitamin is readily excreted. Thus, in this case there is less possibility of toxic
symptoms from taking large doses of these types of vitamins. Caution: This is not the
case for the fat-soluble vitamins. They are absorbed by the fat in the body and are not
easily excreted, thus toxicities are possible when people take excess vitamin supplements.
Toxic symptoms are generally not seen when vitamins are obtained solely from food.
The vitamin levels in the fruits, a nut, and berry shown in Figure 2.20 are obtained
by summing all the vitamins and thus do not show the relative levels of each individual
