The Roles of Vitamin A in the Body
It was long thought that acne was directly related to a teenager’s diet. A teenager with acne was commonly counselled to avoid such foods as chocolate, french fries, and soft drinks often with no relief in the severity of the acne. It is now known that stress, lack of sleep, and the hormonal changes associated with puberty and the menstrual cycle are more likely to cause acne than specific foods in the diet.
While a specific food may not directly affect the presence and severity of acne, a balanced and varied diet will ensure the body is getting all the nutrients it needs to maintain the integrity of the skin. Due to the fact that skin cells are produced and die every few days, the skin is a reflection of a person’s nutritional status. Dietary deficiencies can leave a person more susceptible to skin disorders such as psoriasis, dermatitis, and eczema. Some of the vitamins and minerals that contribute to the healthy skin include the B vitamins, vitamins A, D, and C, and the minerals selenium and zinc.
What Vitamin A Does for Us
Vitamin A is of specific interest because of its role in the maintenance of epithelial tissue (which includes the skin) and vision. Vitamin A, a fat-soluble vitamin, is actually a group of substances that include retinol, retinal, retinoic acid, and the carotenoids. The different forms of vitamin A are used by the body for vision and in regulating the growth, differentiation, reproduction, and maintenance of epithelial tissues.
Even though the term vitamin A is sometimes used interchangeably to refer to the different forms of the vitamin, each substance has specific functions within the body. The retinoids, which include retinol, retinal, and retinoic acid are considered the active or performed forms of the vitamin. Retinol and retinal can be interconverted and are important in all vitamin A functions. Once in the body, retinol or retinal can be further metabolised to produce retinoic acid, but once the retinoic acid is formed it cannot be converted back. Retinoic acid does not play a role in vision or reproduction but can replace retinol in growth and differentiation functions.
The provitamin or precursor forms of vitamin A include the carotenoids, with the predominant dietary carotenoid being beta-carotene. The carotenoids can either be converted to the active forms of vitamin A or utilised for their antioxidant properties. The retinoids are primarily found in animal tissue, whereas the carotenoids are found in dark green and orange vegetables and fruits.
Supports the Immune System
Vitamin A plays an important role in cell differentiation. Cell differentiation is the process by which cells change to take on specialised functions. As mentioned earlier, vitamin A is necessary for the maintenance of epithelial tissue. Epithelial tissue makes up the skin, and the lining of the eyes, intestines, lungs, and bladder. One of the specialised functions of epithelial tissue is to secrete mucus, a lubricating substance which protects against infection. If the cells are lacking in vitamin A, they deteriorate and are replaced with cells that produce keratin instead of mucus. Keratin is a hard protein normally found in hair and nails.
Vitamin A deficiency will cause cells which normally produce mucus to become hard and dry, lose the protective properties associated with the mucus production, and become more susceptible to infection. Cell differentiation is also important to proper immune system function. Vitamin A is required for the differentiation of cells involved in immunity. Vitamin A is also involved in the vision process. The retinal form of vitamin A is involved in rhodopsin formation which is responsible for visual dark adaptation.
While it is true that a vitamin A deficiency will have negative effects on vision and skin health, it has not been shown that taking vitamin A supplements in excess of the recommended intake will improve vision or promote healthier skin. Excess intake of preformed vitamin A can be toxic. Excessive intakes of preformed vitamin A during pregnancy have been shown to cause birth defects. Unlike preformed vitamin A, the carotenoids appear to be nontoxic. This is due to the fact that their absorption from the diet decreases with higher dosages, and once in the body, their conversion to the retinoids is limited.
Because of vitamin As a role in maintaining the integrity of the skin, it has been used as a treatment for acne. One form of vitamin A is used in the drug called Retin A. Retin A is applied topically in the treatment of acne. Along with reducing acne, this drug also tightens the skin, thus reducing the wrinkles associated with ageing. There are side effects associated with this drug, which includes increased sensitivity to the sun, and dry, peeling skin.
Another drug that is used for severe forms of acne is Accutane. Accutane, a prescribed oral medication, is a modified form of retinoic acid, making it less toxic than the unmodified form of retinoic acid. Even so, Accutane tends to have similar symptoms as vitamin A toxicity such as dryness of the eyes and mouth and altered liver function. Neither Accutane or Retin-A should be used right before or during pregnancy. Also, large doses of vitamin A supplements will cause toxicity and should not be taken as a treatment for acne.
The best way to ensure you are getting an adequate intake of vitamin A is to eat a healthful, balanced, and varied diet. Supplementation with vitamin A is typically not required for healthy individuals eating a balanced diet.