Hypervitaminosis

Vitamins are good for you. Therefore even more vitamins are even better. This appears to be the erroneous philosophy expounded by some, especially the "health foods" industry. It is as fundamentally flawed as the concept that anything "natural" is entirely beneficial and devoid of adverse effects. There is still a public perception that megadosage vitamin C is beneficial for the common cold despite the overwhelming evidence to the contrary. The fact that many expensive proprietary preparations of paracetamol, which does help the symptoms of viral infection, also contain vitamin C, bolsters this myth. By and large, excessive dosage of water soluble vitamins is only a waste of money as excesses of water soluble vitamins such as vitamin C are just excreted in the urine. Most fat soluble vitamins are toxic in excess. Overdose may result from strange diets or from the belief that the more the better is applicable. Hypervitaminosis A Vitamin A is present as fatty-acid esters in food sources such as liver, kidney, and milk, and as provitamin A carotenoids in plants usually as β-Carotene. High intake of β-Carotene (hypercarotenaemia) can colour the skin yellow, sparing the eyes, in contrast to jaundice where the sclera is also yellow. Vitamin A toxicity can be acute or chronic. It is well absorbed and there is no effective mechanism for removing or metabolising large amounts. Adults require 500 μg retinol equivalents/day, children 250-350μg /day. Pregnant women should not exceed their recommended intake of 600μg /day. High doses of vitamin A can be teratogenic.1 Acute hypervitaminosis A This is usually from a large overdose such as in eating polar bear's liver that is known to be exceptionally high in the vitamin. Symptoms include: * Headache * Abdominal pain * Nausea or vomiting * Lethargy * Visual changes * Impaired consciousness There are features suggestive of raised intracranial pressure such as bulging fontanelle in an infant, papilloedema and diplopia. Anaemia and thrombocytopenia have also been described.2 Chronic hypervitaminosis A This requires in excess of 50,000 units/day for more than 3 months. Symptoms often include bone pain and bony swelling due to increased bone resorption and periosteal bone formation, often associated with hypercalcaemia. Other symptoms can be quite non-specific: * Scaly seborrhoic eczema * Patchy hair loss * Stomatitis * Loss of appetite * Nausea * Vomiting * Malaise * Hepatosplenomegaly * Raised intracranial pressure Children can present with craniotabes, irritability, failure to thrive, decreased appetite and pruritis. Craniotabes is abnormally soft bones of the skull and is unrelated to tabes dorsalis. Complications include: * Hypercalcaemia * Hypercalciuria and renal stones * Benign intracranial hypertension * Increased bone fragility with increased risk of fractures It may be unwise to give Vitamin A supplements to older patients with good diets, particularly if at risk of osteoporosis.3