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Vitamin A is found only in yellow animal fats, in egg-yolk, milk and cheese. It is particularly
plentiful in fish-liver oils, hence fish-liver oils are used for preventing and curing illness caused
by lack of vitamin A. In a well-fed, healthy human being, the liver can store up sufficient
vitamin A to meet the body's requirements for six months.
Although vitamin A itself is not present in plants, many plants produce a substance called
carotene, formed from leaf-green which our bodies can convert into vitamin A. Carotene is
the yellowish-red coloring matter in carrots. The greener a leaf is, the more carotene it usually
contains. Hence the importance of green, leafy vegetables in the diet as a source of carotene.
Tomatoes, papayas, mangoes and bananas contain more carotene than most other fruits. Red
palm oil contains so much carotene that it is used instead of cod-liver oil. Thus, it is very
valuable, both as a food-fat and for deep-frying.
Vitamin A and carotene are insoluble in water and they are not destroyed by heat unless
oxygen is present. Boiling in water, therefore, does not destroy much vitamin A or carotene.
Vitamin A encourages healthy growth and physical fitness. Young animals soon stop growing
and die if vitamin A is not present in their diet. This vitamin keeps the moist surfaces lining
the digestive canal, the lungs and air passages healthy. It also helps keep the ducts of the
various glands, the tissue that lines the eyelids and covers the front of the eyeball functional.
As vitamin A helps these tissues build up resistance to infection, it is often called the anti-infective vitamin.
Some of the most common disorders in people are caused by a shortage of vitamin A, when
the moist tissues become dry and rough. This often causes serious eye disease, followed by
infection of the air-passages. The skin may also become
flaky and rough. Another defect caused
by shortage of vitamin A is 'night-blindness', when the affected person has
distinct vision only
in bright light.
As the body cannot produce vitamin A, it has to come from external sources. Thus a well-balanced diet is required and is usually sufficient to provide the necessary amount. There is
therefore no need to supplement the need in the form of pills.
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