Vitamin A toxicity (Hypervitaminosis A).
Hypervitaminosis is the excessive accumulation of a vitamin  into the body. Vitamin A is fat-soluble. In cases of excessive dosages, the vitamin can build up in toxic levels in the body fat, since it cannot be excreted in urine through the kidneys. The toxic intake level for vitamin A is 19,500 RAE or 50,000 IU per day.
It has to be mentioned that large amounts of carotenoids, derived from plants, are not as toxic as retinyl esters which are contained in animal origin products. Both, carotenoids and retinyl esters are vitamin A precursors.
There are two types of vitamin A toxicity; the acute one which is caused by too much uptake of vitamin A over a short period of time and the chronic type that occurs, when the excess of the vitamin is present over a longer period of time.
Treatment requires simply the discontinuation of the excessive use of vitamin A. Full recovery must be expected, as soon as the dose of vitamin A taken is adjusted to the proper levels.
The consequences of vitamin toxicity, if untreated, can cause numerous medical problems and it may be potentially fatal.
Increased intracranial pressure has been reported in both acute and chronic types of hypervitaminosis. Liver malfunction, central nervous system disorders, high blood calcium level and kidney problems may be the most important complications. Osteoporosis may occur due to reduced bone density that vitamin A deficiency can result in due to calcium depletion. Recent studies show that too much vitamin A, taken during pregnancy, can cause abnormal development in the fetus.
Symptoms of vitamin A toxicity.
In an infant, the sudden intake of excessive dose of vitamin A may cause a bulging fontanel, which is a soft spot on the head, and its symptoms resemble those of a brain tumor. This group of symptoms is called "pseudotumor cerebri" and they include, apart from the bulging fontanel, drowsiness, vomiting and papilledema. The latest is a swelling of the optic disc.
The symptoms of acute hypervitaminosis in adults are less specific. Headache, nausea, vomiting, double or blurry vision, dizziness, inability of muscular coordination and impaired consciousness may occur.
Bone pain is quite common, often associated with high levels of calcium in the blood. Other symptoms include hair loss, high bad cholesterol level, fatigue, malaise, decreased appetite, poor weight gain, cracking at the corners of the mouth, itchy and oily skin or hair.
Prevention of vitamin A toxicity.
Dose more than the recommended dietary allowance of vitamin A must be avoided. Recent emphasis on vitamin A and beta-carotene as anti-cancer substances may lead to chronic hypervitaminosis, if people increase the dosage beyond recommended figures. |
