Many think that vitamin intake is never enough and that the body can only benefit from a vitamin boost. Is that really the case? Actually not. Under most circumstances, a balanced diet already provides the required amount of vitamins, and the eventual surplus is just eliminated without this impacting the body in any significant way.
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.
Which of the following vitamins is most likely to be associated with toxicity (hyoervitaminosis) following excessive intake:
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.