Nutrition Science and Everyday Application - beta v 0.1

490 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
cells in the skin overproduce the protein keratin (similar to what happens in the eye with
xerophthalmia) causing the skin to become rough and irritated.
Vitamin A deficiency is rare in developed countries, but globally, it is the leading cause
of preventable blindness in children. It is caused by malnutrition related to consumption
of inadequate diets predominantly based on staple grains and lacking in animal products,
fruits, vegetables, and fat, which increases absorption of vitamin A. According to the World
Health Organization, an estimated 250,000 to 500,000 children lose their sight each year due
to vitamin A deficiency, and half of them die within a year of developing blindness, likely
due to infection. 2 According to UNICEF, 30% of children under 5 have vitamin A deficiency
in the world, but rates are as high as 44% and 48% in south Asia and sub-Saharan Africa,
respectively. 4
Figure 8.23. The worldwide prevalence of vitamin A deficiency in 1995-2005, based on World
Health Organization data.
Vitamin A toxicity causes dry, itchy skin, loss of appetite, dizziness, nausea, swelling of the
brain, and joint pain. In the most severe cases, it can cause liver damage, coma, and death.
Vitamin A toxicity is almost always caused by taking supplements in doses above the UL of
3,000 micrograms per day for substantial periods. These high doses would not be found in a
normal diet, although vitamin A toxicity has been observed in Arctic explorers who ate large
amounts of bear and seal liver. 4
Consuming excessive amounts of vitamin A during pregnancy can also cause birth defects,
so pregnant people should pay close attention to vitamin A contained in supplements. In