Vitamin A is a pale yellow primary alcohol derived from carotene. It affects the formation and maintenance of skin, mucous membranes, bones, and teeth; vision; and reproduction. An early symptom of deficiency is night blindness (difficulty in adapting to darkness). Other symptoms are excessive skin dryness; lack of mucous membrane secretion, causing susceptibility to bacterial invasion; and dryness of the eyes due to a malfunctioning of the tear glands, which is a major cause of blindness in children in developing countries.
The body obtains vitamin A in two ways. One is by
manufacturing it from carotene, a vitamin precursor found in such vegetables as
carrots, broccoli, squash, spinach, kale, and sweet potatoes. The other is by
absorbing ready-made vitamin A from plant-eating organisms. In animal form,
vitamin A is found in milk, butter, cheese, egg yolk, liver, and fish-liver oil.
Although one-third of American children are believed to consume less than the
recommended allowance of vitamin A, sufficient amounts can be obtained in a
normally balanced diet rather than through supplements. Excess vitamin A can
interfere with growth, stop menstruation, damage red blood corpuscles, and cause
skin rashes, headaches, nausea, and jaundice.
|Vitamin A||The B Vitamins||Vitamin C||Ascorbic Acid|
|Vitamin D||Vitamin E||Vitamin K|