The need to consume foods rich in vitamins and minerals cannot be overemphasized. In fact, most of the ill health conditions that we face in this period is usually due to reduced or low consumption levels of a specific vitamin/mineral or a group of them. A typical example is night blindness, a disease condition which is caused by lack of vitamin A.
Having said that, it is clear to me that many people are unaware of the health implications of consuming excess vitamins on daily basis. The excess vitamin you take has no advantage whatsoever to your overall health.
There are basically two main groups of vitamins; water soluble and fat soluble vitamin. They are named based on how these vitamins are stored and dissolved in the body. In the case of vitamin A which is a water soluble vitamin, there had been indications of it causing birth defect in pregnant women when consumed in excess amount on daily basis.
No doubt that the vitamin is needed for night vision, immune system function and healthy growth but one has to be mindful of the danger associated with excess consumption. The recommended dietary allowance for vitamin A for adults males older than 19 is 900 mcg and for adult females is 700 mcg for females. A condition of Vitamin A toxicity is known as hypervitaminosis and may occur after taking excessive amounts of vitamin A for a long time.
For most of all these vitamins, water or fat soluble, the symptoms of excessive consumption include fatigue, reduced appetite, nausea, dizziness, headache and dry skin. In very rare and severe cases, hypervitaminosis may cause the damage of internal organs like liver.
My recommendation to you is that if you must raise your vitamin level via supplementation, there is need for you to speak to a medical doctor. You should note that some of our daily meals already contains certain vitamins and some of the processed foods are vitamin fortified. Supplementation has to be properly administered in such a way that it will not to give room for excess intake.