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.
Summary: Vitamin A is found only
in certain food substances. It is also abundant in fish-liver oils. Our liver
is able to store some vitamin A to meet our requirements. Carotene, is a
substance which our bodies can convert into vitamin A. It is found in green
leafy vegetables, carrots and some fruits. Vitamin A is not easily destroyed by
heat. It is essential for healthy growth and physical fitness. It also helps keep
the eyes from infection. A lack of vitamin A could lead to eye diseases and
skin disorders. Thus, a well-balanced diet is needed to ensure that the body
receives the necessary supply of vitamin !. It is not necessary to take extra
supplements.
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