Vitamin A is a group of chemical compounds of similar structure and functions in the body. A biological, active form of vitamin A is retinol. Together with its derivatives: retinal (aldehyde form) and retinoic acid (acid form) it belongs to retinoids. Vitamin A belongs to the vitamins well soluble in fats, its main place of storage is in the liver and adipose tissue.
The body’s requirement of vitamin A is dependent on gender, age and physiological state. According to the recommendations of the Instytut Żywności i Żywienia in Warsaw, daily requirement for this vitamin in adult women is 0,8 mg, and in men- 1 mg. Women who are pregnant and lactating should intake 1 mg and 1,2 mg per day. People living under stress, digestive diseases or long-term infections should intake larger amounts of vitamin A. The correct concentration of vitamin A in the blood serum is 0,3 – 0,6 mg/l (1,0 – 2,1 µmol/l).
Vitamin A deficiency (hypervitaminosis) can contribute:
- drying of the cornea and conjunctiva,
- turbidity and soften the cornea,
- the creation of the so called “night blindness”,
- excessive keratinization of the epidermis,
- the proper functioning of the epithelial tissue disorders (excessive flaking epithelium may contribute to the formation of stones in the urinary tract),
- bone fragility and hair loss.
Providing adequate amounts of vitamin A is extremely important due to its wide range of activities in the body. One of the main functions of vitamin A int the human body is its impact on the proper functioning of the skin. It takes place mainly through:
- its participation in the proliferative processes and cells differentiation of the epidermis,
- keratinization (swelling) of epidermis, which main target is to produce keratin and the movement of cells from basal layer to stratum corneum,
- stimulating the dermis and improve its elasticity,
- antioxidant activity and delaying the aging process,
- proper nutrition of the skin,
- antiseborrhoeic and anti-acne activity.
Vitamin A also takes part in receiving visual stimuli and process of vision (retinal is a component of the red visual), cell metabolism has anti-inflammatory properties. It also prevents and slows down the progression of cancer (mainly the colon, lungs, prostate and breast), by protecting against mutagenesis, DNA damage and thanks to the vitamin A- ant-proliferative. In addition, it is involved in the synthesis of steroid hormones and stimulate the bone marrow to produce red blood cells. Vitamin A also speeds up the healing process of wounds, stimulates immunity and affects the fertility and normal development of the embryo.
Vitamin A is delivered into the body primarily with food. Its primary source is diet rich in fats. Vitamin A is found in animal products such as: oil, butter, milk, eggs, yolk. In turn β-carotene is the precursor to vitamin A, it is a component of many plant products: vegetables (carrot, pumpkin, peppers, spinach, broccoli, tomatoes) and fruits (peaches, oranges, cherries).
Absorption of vitamin A takes place in the gut and only in presence of fats. However it may be aided by some elements such as: calcium, phosphorous, zinc and vitamins B, C, D and E. In turn the caffeine, nicotine, alcohol or steroids can contribute to the deterioration of the absorption process of vitamin A.
Deficiencies of vitamin A in the developed world, are the consequence of inadequate diet, malabsorption and animal fats. Therefore, in order to provide the body with adequate doses of this vitamin, supplementation is required. Preparation containing viamin A, may assis the process of the treatment of skin disorders such as acne, proriasis, actinic keratosis, senile or sunburn.
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