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  • Created by: Jani
  • Created on: 24-05-11 12:23

Fat Soluble Vitamins

Vitamin A

Comes in two forms:

Retinol - animal foods   

Beta Carotene - plant foods

Sources:

Retinol – milk, cheese, egg yolk, butter, oily fish

Since 1954, vitamin A has been added to margarine by laws to make margarine nutritionally equivalent to butter.

Beta Carotene – carrots, mangoes, apricots and melon. The darker the green the vegetable is the more beta carotene it contains.

Functions:

·         Required to make a substance called RHODOPSIN (visual purple). This pigment is found in the retina and required for vision in dim light.

·         Required to keep the mucous membranes in the cornea at the front of the eye and the lining of the respiratory and digestive tracts moist and free from infection.

·         Required for maintenance and health of skin.

·         Required for growth and maintenance of all body cells (important for normal growth of children)

·         Important in protecting against cancer (ACE)

Recommended Intake:

700 µg for men

600 µg for women

 Women need an extra 100µg during pregnancy

                          950µg per day during lactation

Deficiency:

Rare, signs of deficiency are: children’s growth retarded, night blindness, bacterial invasion and permanent scarring of the cornea of the eye – XEROPHTHALMIA.

Excess:

·         Toxicity can occur when vitamin A is stored in the liver

·         Hypervitaminosis A – causes drowsiness, irritability, skin and bone disorders and an enlarged liver.

·         Pregnant women are advised not to eat liver pr take vitamin A supplements as too much can lead to birth defects.

·         Factors affecting absorption:

·         Low protein or fat intake will adversely affect metabolism and absorption

Effects of cooking & storage:

·         Both retinol & beta carotene are unaffected by most cooking methods. Retinol in fatty foods may be lost through oxidation, this is prevented by the use of antioxidants, by refrigeration and exclusion of light.

Vitamin D

(cholecalciferol)

White crystalline compound which is soluble in fats and oils but is insoluble in water.

 

Also comes in 2 forms:

Cholecalciferol (D3), this is the natural form of the vitamin occurring in foods. Formed by the action of sunlight.

Ergocalciferol (D2), synthetic form of the vitamin which has the same activity as the natural vitamin.

Sources:

·         Food- although found in relatively few foods. It occurs naturally in foods of animal origin. Fish liver oils are very rich, dietary supplements rather than foods.

o   The content in milk varies with the time of year but even summer milk is a relatively low source. Although milk is low in vitamin D it is consumed in large quantities, making it a useful source.

o   Vitamins D content in margarine is greater than that of butter since in Britain margarine is enriched with Vitamin D.

·         Sunlight, formed in the skin on exposure to sunlight. Formation of Vitamin D varies with latitude and the amount of time the person spends in the sun. The quantity of…

Comments

mevans5152

Thanks for this - a great summary of vitamins

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