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Functions

100

Cell Growth

Retinoic acid found in vitamin A is a growth factor epithelial cells and other cell types in the body.

200

Immune system

Vitamin A is essential for maintaining healthy immune function and defficiency can lead to an impaired response to infection.

300

Vision

Vitamin A is required for the maintenance for normal vision. Retinal, a form of vitamin A in the eyes, is combined with a protein called opsin to give rhodopsin, a essential light absorbing molecule needed for color vision and seeing in dim light.

400

Gene Transcription

Vitamin A in the form of retinoic acid is essential for gene transcription. Retinol is taken up by the cell where it is then oxidized to retinaldehyde which is then oxidized to give retinoic acid. Retinoic acid binds to nuclear receptors called in order to regulate gene transcription.

500

Skin Health

Retionic acid also maintains skin health by activating genes that cause immature skin to develop into mature epidermal cells. Currently the retionic isotretinoin is the most commonly prescribed agent in the treatment of acne. This also reduces the amount of bacteria present in the ducts and surface of the skin, which occurs therefore it results to a reduced sebum, which is a source of nutrients that bacteria relies on.

Deficiency

100

Primary Deficiency

This is caused by prolonged dietary deficiency, particularly where rice is the staple food.

200

Secondary Deficiency

Is when there are problems in converting carotene to vitamin A, or reduced absorption, storage, or transport of vitamin A.

300

Signs and Symptoms

An early symptom, is impaired dark adaptation of the eyes, which can cause to night blindness. Drying, scaling, and follicular thickening of the skin and respiratory infections may occur. As well as generally impaired immunity. The younger the patient, the more severe are the effects of vitamin A deficiency.

400

Prevention

Eating at least 5 servings of fruits and vegetables per day is recommended in order to provide the right amount of carotenoids needed. Carotenoids are absorbed better when consumed with some dietary fat.

500

Treatment

Dietary deficiency is traditionally treated with vitamin A palmitate, that is available in oils or dry forms. It is a common vitamin supplement that comes in oral and injectable forms for treatment.

Overdose

100

Forms of Vitamin A Overconsumption

Acute Hypervitaminosis A and Chronic Hypervitaminosis A

200

Acute Hypervitaminosis A

Occurs when too much vitamin A is taken at one time. It can lead to the formation of rashes, headaches, increased pressure in your skull, drowsiness, nausea, vomiting, irritability, blurred vision, stomach pains and a lack of muscle coordination.

300

Chronic Hypervitaminosis A

Occurs when large amounts of vitamin A build up in the body over a long period of time. With these high amounts of vitamin A in the body, toxicity begins to develop.

400

Symptoms

Immediate effects include hair loss, dry, rough skin and hair, dry eyes and cracked lips. If early symptoms are not treated, this condition can lead to severe headaches, feelings of weakness, liver abnormalities, central nervous system disorders and birth defects in children of pregnant women.

500

Hair loss

Table 1: Recommended Dietary Allowances (RDAs) for Vitamin A [5] Age Male Female Pregnancy Lactation 0–6 months* 400 mcg RAE 400 mcg RAE 7–12 months* 500 mcg RAE 500 mcg RAE 1–3 years 300 mcg RAE 300 mcg RAE 4–8 years 400 mcg RAE 400 mcg RAE 9–13 years 600 mcg RAE 600 mcg RAE 14–18 years 900 mcg RAE 700 mcg RAE 750 mcg RAE 1,200 mcg RAE 19–50 years 900 mcg RAE 700 mcg RAE 770 mcg RAE 1,300 mcg RAE 51+ years 900 mcg RAE 700 mcg RAE