Vitamin A
Vitamin A (retinol) functions in reproduction, growth, the maintenance of skin and mucous membranes and the visual process.
Vitamin A is normally transported in the blood linked to a specific protein, retinol binding protein (RBP).
Specific proteins on cell surfaces and within cells are also involved with intracellular transport of the vitamin.
Vitamin A is fat soluble and is primarily stored in the liver, where RBP is synthesized. In a well nourished person, vitamin A stores are generally sufficient to last many months on a vitamins A-deficient diet before signs of deficiency appear.
The initial symptoms of vitamin A deficiency are night blindness and keratinization of hair follicles.
Continued deficiency leads to damage to eye tissue and irreversible blindness.
The US recommended Daily Allowance (RDA) of vitamin A for adults is 5000 IU (1000 retinol equivalents).
Rich dietary sources of retinol (preformed vitamin A) include dairy products, eggs and organ meats.
Some carotenoids (found in deep-yellow and dark green vegetables) can be converted to vitamin A during digestion.
In the US diet, approximately half of the vitamin A activity is derived from B-carotene and other carotenoids.
Vitamin A
Nutrition is a scientific discipline that encompasses a structured body of knowledge. It includes various fields such as clinical nutrition, community nutrition, public health, food policy, and food science. At its core, nutrition is the study of how the body utilizes food. It is essential to life. Understanding nutrition enables us to make better dietary choices by determining the necessary nutrient intake, identifying optimal food sources, and recognizing beneficial or harmful food components.
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