Vitamin A, the first vitamin that was soluble in fat was discovered in 1913. It is essential for upkeep and maintenance of healthy skin, bones, tissues, teeth and essentially for the eye. Retinol, a form of Vitamin A, which aids vision, especially in low light, is produced in the retina. It is also necessary for colour vision. It is also called “anti-infective” vitamin because it assists the immune system of the body.
Vitamin A exists in the body in the form of Retinol and carotenes in the body. Retinol is absorbed by consuming animal food sources. The pure form being unstable, it is found as retinyl ester in tissues. Carotenes, alpha, beta and gamma and xanthophylls beta cryptoxanthin function in herbivores and omnivores. These are converted to retinal with the help of enzymes.
Retinol occurs in foods of animal origin, fruits and vegetables with carotenoids, which are orange, yellow and red in color.
Being fat-soluble, disposing off excess Vitamin A is harder than the other water-soluble vitamins. Acute cases of toxicity occurs upon consuming 4,000 IU per kg of body weight everyday for 6 to 15 months.
Vitamin A toxicity is called Hypervitaminosis A. It can be of two types, acute- caused by excessive intake for a short period of time and chronic- caused by intake of excess dose over a long period.
Vitamin A toxicity causes reduced appetite, nausea, vomiting, irritability, blurry vision, headaches, hair loss, abdominal pain, muscle cramps weakness, drowsiness, Insomnia, diarrhea, liver damage, yellow discoloration of the skin, abnormal softening of the skull bone in infants and children, and also causes changes in consciousness. In case of severe toxicity, there is hair loss, skin becomes dry, drying of the mucous membrane dries up, weight loss, anemia, fatigue, fever.
Treatment of acne with Isotretinoin also causes some of these symptoms. Pharmaceutical variants of retinoid like 13-cis retinoic acid can cause pseudo tumor cerebri. This causes blurring of vision, confusion and headache, associated with increase in the intracerebral pressure.
Excessive consumption of preformed vitamin A like 1500 RAE may cause of osteoporosis. Vitamin A toxicity affects developing fetuses as well.
When the symptoms for hypervitaminosis A start emerging, the doctor should be consulted and certain tests and exams should be done like bone x-ray, cholesterol and liver function test, blood calcium test and blood tests to determine the Vitamin A level. Whenever people feel that they have consumed too much of it the doctor should be consulted to avoid excess consumption. Reducing or stopping intake can cure hypervitaminosis A.
Medical practitioners believe that the knowledge that consumption of Vitamin A and beta carotene can help in avoiding cancer has resulted in its excess intake which results in toxicity.