However, vitamin intoxication is possible and this condition is known as hypervitaminosis. Hyperavitaminosis is seen almost exclusively in children with an unbalanced diet and taking a lot of supplements or heavily fortified foods.
Due to chemical properties, an excess of vitamins can only be witnessed with certain vitamins, while it's virtually impossible with others, given their high turnover and short half-life.
Hypervitaminosis A usually happens as a consequence of excessive assumption of food supplements (megavitamin therapy).
Sometimes it can be witnessed in people eating large amounts of animal liver and derivatives. Certain drugs used in severe acne, such as isotretinoin, can cause it too, as they contains large amounts of retenyl esters.
Hypervitaminosis A is _not_ caused by high consumption of food rich of provitamin A carotenoids (vegetables).
Symptoms include drowsiness, confusion, irritability, headache, nausea, blurry vision, sun sensitivity, eczema, mouth ulcers, and bone fragility.
The condition is considered benign and under most circumstances resolves with supplement interruption.
Compared to hypervitaminosis, vitamin A deficiency is much more common world-wide, especially among children in 'developing' countries. Elsewhere it's mainly seen as a consequence of GI malabsorption and sometimes renal disease.
@encelado Paracelsus' principle applies yet again. "The dose makes the poison".
#medpolls
Which of the following vitamins is most likely to be associated with toxicity (hyoervitaminosis) following excessive intake: