On a
worldwide basis, about 60% of dietary vitamin A is
estimated to come from pro-vitamin A.
According to Simon (1990) world vitamin A deficiency is
the most common dietary deficiency.
Furthermore, one
million children (6 months to six years old) suffer a severe
enough level of vitamin A deficiency to cause eye
disease, 250,000 of them lose their sight and 150,000 of
them die within several months of becoming blind.