Vitamins A

Vitamin A

What is a vitamin?

A vitamin is an essential, noncaloric, organic compound needed in tiny amount in the diet. Vitamins help the digestion, absorption, and metabolization of other nutrients.

Classes of vitamins: fat -soluble and water- soluble

Fat soluble vitamins –A, D, E, and K- are absorbed into the lymph and travel with the blood. These vitamins are stored in the liver or with other lipids in fatty tissues and in some cases, can build up in toxic condition.

Vitamin A

Functions:

Regulation of gene expression: these activate or deactivate the genes which are needed for protein synthesis which are essential for body function.

Eyesight: when light falls on the cornea, it penetrates the cells of the retina bleaching the molecule of the pigment rhodopsin-the light sensitive pigment of the cell- that lies within these cells. Vitamin A is part of the rhodopsin molecule; thus it gets destroyed each time light enters the retina. If vitamins A is not replenish, a lag-longer than usual-occurs before you can see again after a flash of light at night- night blindness. This signifies a deficiency in vitamin A.

Another deficiency of vitamin A is exhibited when the protein keratin accumulates and clouds the cornea- the vitamin dependent part. If not correct, it can lead to drying and then to thickening and permanent blindness. If it is discovered early, capsule providing 60, 000 microgram of vitamin twice yearly can reverse it. Or to prevent this, a child can be fed a variety of fruits and vegetables regularly.

Skin and body lining: Vitamin A is needed for both internal and external lining. The skin and interior lining of the: lung, intestine, vagina, urinary tract and bladder serves as a protective barrier to microbes. Vitamin A aids in cell differentiation- which is the process by which immature cells mature and perform specific functions associated with their cell type. Goblet cells that line the interior of organs, for example secretes mucus to moisten and protect against invading microbes. In the outer layer, it helps to protect against skin damage.

If there is a deficiency, vitamin A dependent cells die and are removed by cells that secretes keratin. Keratin makes tissue surface dry, hard and cracked. As dead cells accumulate, the surface becomes more vulnerable to infection. Respiratory infections are more likely to occur; as well as vaginal infection.

Immunity: It’s an anti-infective vitamin because much of the body’s defensive mechanism relies on sufficient supply. With great deficiency- measles become severe and if not corrected can lead to blindness even after measles is cure.

Growth: Vitamin A assists in growth of bones and teeth.In children, failure to grow is a sign of vitamin A deficiency. Vitamin A supplements is imperative but dietary change is also important for growth and weight gain.

Vitamin A deficiency: decrease immunity; vulnerability to infection; etc.

Vitamin A toxicity: symptoms include: nausea, vomiting, diarrhea, joint pain, loss of coordination, rash, hair loss, stunted growth, possibly damage to the liver and enlarge of the spleen.

Earliest symptom of overdose include: appetite loss, dizziness, blurred vision, headache, itching of the skin, and irritability. Over the years, excessive intake of vitamin A can weaken the bone and lead to hip fracture. Supplements providing three to four times the recommended dose can cause birth defect. Teenagers are misinformed sometimes that Vitamin A can cure acne. Vitamin A itself has no effect on acne. Accutane –an acne medicine- made from vitamin A has been modified chemically- thus its useful effect to treat acne. Food naturally rich with vitamin A pose no risk, other than liver. An ounce of beef or pork delivers three times the dietary recommended intake and thus should be avoided on a daily basis. Children and pregnant mothers are at greater risk for developing toxicity from vitamin A.

Vitamin A recommendation: Because vitamin A is stored in the tissue, it does not have to be consumed on a daily basis.The recommended amount is base on weight. Therefore, a man is required 900 micrograms while a woman requires micrograms-higher during lactation. Children need less. A regular balance diet with the recommended fruits and vegetables is adequate for the recommended amount.

Food source of vitamin A: Active vitamin A is found in animal food source only- the richest source being liver and fish oil. Milk and milk products such as cereal to which vitamin A are added can be a good source. Vitamin A is present in plant food, but as precursors. Meaning, when consume, it has to be broken down into an active source of vitamin A by the body. For example, bright fruits and vegetables contain vitamin A.