Functions
Vitamin A is fat-soluble and capable of accumulating in the body. Its functions are related to growth and protein synthesis, the maintenance of bones, mucous membranes, sight and skin, and protection against anemia and infection.
Sources
Vitamin A occurs as retinol in animal foods (from retina, see below), but also as carotene and carotenoids, precursors of the vitamin and which the body can convert into vitamin A, compounds found exclusively in plant foods. The best source of provitamin A is carrots. Other good sources are colored fruits and vegetables, green leafy vegetables such as kale and spinach, but also melons, squash, tomatoes, yams, etc. Excessive amounts of carotenoids in the diet may color yellow the forehead, nose, chin and palms especially of children, but this is not harmful and simply a sign to switch for a while to other foods. By far the best source of retinol is the oil extracted from fish livers, such as cod-liver oil. But this requires caution and supervision as it may be damaging to the liver and spleen.
Uses
- Anti-infective agent
- Counteraction of night blindness
- Improvement of tissue oxygenation
- Nourishment of skin and hair and control of acne
- Prevention of eye disease and improvement of weak eye-sight
- Protection against air pollution
- Promotion of growth, vitality and well-being
- Resistance to infections
- Secretion of gastric juices for protein digestion
- Stability of cell membranes and mucous linings controlling aging
Deficiency
- Accelerated aging and senility
- Eye inflammation, night blindness, poor vision
- Skin disorders like acne, boils, pimples, dryness and scales
- Brittle hair, dandruff and hair loss
- Weak defective teeth and gums
- Susceptibility to respiratory infections such as flu and colds
- Lack of appetite, lassitude, low vigor
- Retarded growth in infancy and childhood
Safety
Sufficiently safe to be considered indispensable for pregnant and lactating women. Nevertheless, being a fat-soluble vitamin and capable of accumulating in the body, it requires caution. Adult doses of over 85,000 IU per day may quickly turn toxic, a state characterized by dizziness, headache, nausea and vomiting.