Vitamin A

Any of a group of substances found in very small amounts in most foods is a vitamin. A well-balanced, varied diet contains all the vitamins normally needed for health. Vitamins in excess of what the body needs do not increase health or well-being, and may actually produce illness. A poor diet cannot be corrected simply by taking vitamin concentrates.

Vitamin A plays a part in the chemical reaction that take place in the retina of the eye when it is stimulated by light. Vitamin A is essential to vision. Lack of Vitamin A can lead to xerophthalmia and to poor vision in dim light (night blindness). Vitamin A is found in all animal tissues, but it is especially abundant in fish liver oil. An indirect source of Vitamin A is a substance called carotene, which the body can convert into Vitamin A. Carrots and orange-colored fruits and vegetables contain plentiful amounts of carotene. If pure Vitamin A concentrate is taken daily in large amounts, it can lead to severe disorders of the nervous system, bones, and other tissues.

Xerophthalmia is a condition of the eye in which the cornea is dry and may become inflamed and ulcerated. Xerophthalmia is caused by a lack of Vitamin A in the diet. The condition also dries out the conjunctiva (the membranes lining the eyelids and the front of the eyeball) and slows down the production of tears by the tear glands.

Carotene is any of several related orange pigments that are utilized by the body to form Vitamin A. Carotene compounds are present in all plants and are essential in the diet. Foodstuffs with a distinct orange or yellow color, such as carrots, sweet potatoes, egg yolks, and butter, are specially rich in carotene.