Description

The fat soluble vitamins A and E are hydrophobic. Vitamin
A which has numerous functions, is carried by a specific carrier,
retinol binding protein while vitamin E and carotenoids are
carried by lipoproteins. Vitamin A is ingested as retinyl
esters and is also produced from the metabolism of the pro-vitamin
A carotenoids, b-carotene and b-cryptoxanthin.
Lycopene, a carotenoid from tomatoes, has high anti-oxidant
activity, but cannot be converted to vitamin A. About 20%
of persons ingesting high levels of b-carotene
develop hypercarotenaemia, with yellow discoloration of the
skin. The diagnosis of hypercarotenaemia requires serum to
be assayed for all carotenoids.

Vitamin E is ubiquitous in the diet and deficiency is
caused by fat malabsorption especially with biliary problems.
Vitamin E is a potent anti-oxidant in many tissues and low
concentrations result in damage to red cells, lungs, retina
and nervous tissues.

Malabsorption of fat also results in malabsorption of
the fat soluble vitamins. Therefore in all malabsorption states,
serum concentration of vitamins A, E and carotenoids should
be measured.