Vitamin A- FAT SOLUBLE- STORED IN BODY- DON'T NEED DAILY Flashcards
State the two types of Vitamin A
Retinol- animal source
Beta Carotene- plant source
In the British Diet, 2/3 of Vitamin A are consumed as Retinol and 1/3 is consumed as Beta Carotene.
State sources of Retinol (animal sources)
Milk, Egg yolk, Oily fish (herring)
Since 1954, margarine has been fortified with Vitamin A- make it nutritionally equivalent to butter.
State sources of Beta Carotene (plant sources)
Oranges, mangoes (orange foods)
The darker the green vegetable, the more Beta Carotene it contains
Describe the functions of Vitamin A
1). Vitamin A is required to make a substance called RHODOPSIN (visual purple). It is a pigment found in the retina of the eye and is necessary for vision in dim light.
2). Vitamin A is required to keep the MUCOUS MEMBRANE in the cornea of the eye and the LINING OF THE RESPIRATORY (nose and throat) and digestive tracts MOIST and FREE from infection.
3). Vitamin A is required for maintenance and good health of the SKIN.
4). Vitamin A is required for growth and maintenance of all BODY CELLS (children as rapid growth)
5). Vitamin A is an antioxidant. It’s function is to strengthen the immune system to fight infections (heart disease and cancer).
6). Research shows that Vitamin A is essential for REPRODUCTIVE PROCESSES in both genders.
7). Vitamin A slows down the AGEING of the skin (wrinkles).
Explain the intake of Vitamin A for a pregnant woman?
700mg- men
600mg- women
Pregnant women need an extra 100mg during the 3rd trimester- meet the needs of the growing baby.
Evidence suggests high retinol levels lead to birth defects- spina bifida.
Pregnant women need to monitor their intake- recommend Pregnacare as a supplement as it is low in Vitamin A)
What is the Deficiency of Vitamin A?
-Deficiency is rare
Signs:
-retarded growth in children
-Night blindness- limited RHODOPSIN
-Health of the skin is affected and resistance to infection is lowered- POOR CONDITION OF THE MUCOUS MEMBRANE AND RESPIRATORY TRACTS
- Bacterial invasion and permanent scarring of the cornea of the eye- XEROPHTHALMIA.
Excess of Vitamin A?
-TOXICITY- this occurs since Vitamin A is STORED in the LIVER- unlikely in a normal diet.
-HYPERVITAMINOSIS A- causes drowsiness, irritability of skin and bone disorders and enlarged liver
-PREGNANT WOMEN- advised not to eat liver/ take Vitamin A supplements- excess leads to birth defects (spina bifida).
-EXCESS- yellowish discolouration of the hands and soles of feet.
Explain the Bioavailability of Vitamin A? (Factors affecting the absorption)
-LOW PROTEIN/FAT INATKE- will adversely affect metabolism and absorption
-FAT SOLUBLE- More available to the body when dissolved in fats
-ACUTE INFECTIONS- appear to lower Vitamin A concentrations in the blood
What are the effects of Vitamin A of Cooking and Storage?
Retinol and Beta Carotene are UNAFFECTED by most cooking methods
-STORAGE- Retinol in fatty foods may be lost- OXIDATION.
This can be prevented with the use of ANTIOXIDANTS and the exclusion of light (wrapping fats in oils).
