Nutrition Science and Everyday Application - beta v 0.1

VITAMINS IMPORTANT FOR VISION 489
deficient populations did not reduce the number of children who contracted these diseases,
but it did decrease the severity of the diseases so that they were less likely to be fatal. Since
this discovery, providing vitamin A supplementation to children in the developing world has
been a major effort of the World Health Organization and UNICEF. 1
Food Sources of Vitamin A and Carotenoids
Preformed vitamin A is found only in animal-derived foods. The best food sources are
liver and fish oils, as vitamin A is fat-soluble and stored in fatty tissues. Smaller amounts can
be found in other animal products, such as meat, eggs, and dairy products.
Provitamin A carotenoids such as beta-carotene are mostly found in fruits and
vegetables. Carotenoids are brightly-colored pigments, so vibrant color is a good indicator
of their presence. Top sources include orange and yellow vegetables such as carrots, sweet
potatoes, and pumpkins (beta-carotene is a bright orange pigment), bell peppers, fruit, leafy
green vegetables, and some vegetable oils. Some carotenoids can also be found in animalderived
foods. For example, the yellow color of egg yolk and butter comes from carotenoids
absorbed from the diets of the hens and cows, respectively.
Figure 8.22. Food sources of vitamin A. Food sources that only contain provitamin A carotenoids
are represented with orange bars. Those containing preformed or active vitamin A (animal-derived
or fortified foods) are represented with purple bars. Source: NIH Office of Dietary Supplements.
Deficiency and Toxicity of Vitamin A and Carotenoids
The main symptoms of vitamin A deficiency are xerophthalmia, night blindness, and
increased susceptibility to infections. Another symptom is hyperkeratosis, which occurs when