Vitamins are groups of chemical susbstance of which are identified as vital to the body.
At first scientist labled each as a letter but once their chemical composition was ascertained it was possible to give them all names.
The body requires only small amounts of each vitamin but it cannot make them by itself. They must be supplied the foods we eat.Vitamins are required to regulate the maintanance and growth of the body and controll metabolic reactions in cells.
Vitamins are classified according to the substances they desolve in. There are two classifications
- Fat Soluble: A,D,E and K
- Water Soluble C and B complex
A diet lacking in one or more vitamins will result in specific difficiency deseases.
Lets take a look at each of these Vitamins:
Vitamin A is a family of the fat soluble vitamins. There are two types of vitamin A:
Retinol and Carotenoids.
These are found in animal and plant food s in particular. Vitamin A is also added to margerine to ensure that people obtain enough.
TYPES OF VITAMIN A
Reinol is one of the most active, usable forms of vitamin A and it is found in animal food such as liver and eggs and in some fortified food products. Retinol is often called preformed vitamin a. It can be converted to retinol and retnoric acid, other active forms of vitamin A family (1-4)Carotenoids:
Some plant foods contain darkly colored pigments called Pro-vitamin A Carotenoids that can be converted to retinol during digestion. Two parts of carotene are required to form one part of retinol. Grass contains carotene so during the summer when more carotene is present, milk from cows will contain more vitamin A than in winter. Approximately 26% and 36% of vitamin A consumed by men is provided by Pro-vitamin A carotenoids.
Beta-Carotene is a Pro-Vitamin A carotenoid that is more efficiently converted to retinol than carotenoids. For example, alpha carotenoid and B-Cryptoxanthin are also converted to vitamin A but only half as efficiently as beta-carotene (1). Lycopene, lutein and zeaxanthin are carotenoids commonty founds in food. they are not sources of Vitamin A but may have other health promoting properties.
IMPORTANCE OF VITAMIN A
Required to make the substances called visual purple, which is formed in the retina of the eye to enable it to see in dim light
- Requied to keep mucos membranes in the throat and digestive system, bronchial and excreetory system moist and free from infection
- Required for the maintanance of the skin
- Required for the normal growth of children, particularly the bones and teeth
Vitamin A plays a very important role in vision, bone growth,reproduction, cell division and cell differenciation, which is the process by which a cell decides what it is going to become.
It helps maintane the surface lining of the eyes and the respiratory, unirary and intestinal tracks. When those linings break down, bacteria can enter the body and cause infection
Vitamin A also helps maintane the integrity of skin and mucos membranes that functions as a barrier to bacteria and viruses.
Vitamstem A helps regulat ehte immune system. The immune system helps prevent or fight off infections by making wite blood cells that destroy harmful bacteria airuses.
Vitamin A may help lymphocytes, a type of white blood cell that fight infections function more normally.
DIFFICIENCY OF VITAMIN A
Xerophthalmia. damage of the cornea of the eye. Vitamin A difficiency contributes to blindness by making the cornea very dry thus promoting damage to the cornea and the retina.
Vitamin A difficiency (VAD) is the leading cause of preventable blindness in children and raises the risk of raises the risk of diseases and death from severe infections. In pregnant women VAD causes night blindness and may increase the risk of mortal maturity.
Vitamin A difficiency is a public health proted by thr high prevalance of night blindneblem especially in Africa and South East Asia. VAD most likely affects pregnant women and children in low income countries.
Crucial for maternal and child servival,supplying adequate Vitamin A in high risk areas can significantly reduce mortality. Conversss durinly its absence causes a wide risk of disease and death .
- For children, lack of vitamin A causes sever visual imparement and blindness, and significantly increases the risk of illness and even death from such common childhood infections and disrrhoea, desease and measels.
- For pregnant women in high risk areas, Vitamin A difficiency occurs especially during the last trimester when demand by both unborn and mother is highest. The mother's difficiency is demonstra the high prevalance of night blindness during this period. VAD may also be associated with elevated mother to child hiv infection.
Signs ans symtoms of Vitamin A difficiency
- Night blindness: The child cannot see dim light, making child to fall over things and not see to eat.
- Bitot's spots: These are foamy, soapy and whitish patches on the white part of the eye (the conjunctiva). They don't affect the sight in day light.
- Conjuctevia xerosis: This means dryness, slight roughness or winkles in the white part of the eye, which are usually wet, smoothe and shiny. Changes of the tear ducts also leads to reduced wet abitity of the eye.
- Corneal lesions: This is when the clear part of the eye is completely damaged. The person cannot see properly and may go blind.Blindness is seriously an irreversable change. It is important to recognise and treat early symptoms.
The body imunity is decreased, which impares the defence of white blood cells against infections. The skin and the cells lining the gut and respiratory tract are less healthy and less able to resist the infection.The infection gets more severe, recovery may take longer and the child is more likely to die.
The ground substance of bone, cartilage and teeth is affected which results in defect formation during growth.
Decreased production of sex harmones results in obnormal sperm in males, low rates of conception and increased rates of still births.
The skin changes more common in children. It give rise to inflammation of the skin appearing as small nodules.
SOURCES OF VITAMIN
Fish (oily fish eg. herring, pilchard, sardene,kidney,cod and holibut-liver-oli)
Liver, Eggs and while milks are good animal sources of vitamin A. Many orange fruits and green vegetables are good sources of pro-vitamin A carotinoids.Including these foods in your diet will help you meet your daily need for vitamin A
In addition, food manifaturers fortify a wide variety of products with vitamin A. Breakfast cereals, pastries, breads, crackers, cereal grain bars, and other foods may be fortified with 10% of the daily value of vitamin A.