Ayesha, in general thal has contionous depletion for all minerals and vitamins because the body is under great stress. Those viamins have many functions but i will just say what may be of concern to thal. So this means that these are NOT the only functions
Calcium & Phosphorus: Both are essential for healthy bones. This is important to thal because usually the bone marrow is active and cause a lot of pressure on bones causing them to be brittle that is why you need to have as much as possible healthy bones. Phosphorus should be present in order for the cell to release energy needed for metabolism
Vitamin A: important in the formation of red blood cells, vision, growth and development, immunity, and one of the most things is that its defiency causes zinc defiency too
Vitamin B:There are lot to say here and there are many vitamin B like B6, B12,.... but they are also important for blood formation, nervous system, gene expression and they act as coenzymes. Their presence is important for the formation of many enzymes. Increase the immunity
Vitamin C:For thal it shouldn't be taken within meals but rather between meals as it helps in the absorption of iron. It should be taken after half an hour from the starting of desferal because it helps to release more iron out of the body. A max dose for a thal is 250mg everday. Though we have to stay away from Vitamin C because of iron , we should not have deficiency in it because it is an antioxidant and can regenerate other antioxidants such as vitamin E . It is important to in the formation of carnatine.
Vitamin D:You have to have it in order to absorb Calcium and Phophrous and therefore vitamin D defiency leads to Osteoporisis. It is important in the secretion of insulin. Helps in growth
Vitamin E:it is an antioxidant, research in Singapore conference said it was safe to take daily up to 600mg but it should be from a natural source. It is very important for thal because they have a very high oxidative stress
Magnesium: makes the red cell membrane stronger and therefore prolonging its life and therefore decreasing hemolysis leading to a decrease in the levels of bilirubin and therefore helps in the less formation of gall stones, important to the heart because togather with calcium regulates the heart beats, it is important in more than 300 reactions in the body
L-Carnitine:Decreases Apoptosis, maintaing healthy muscles and the most important heart muscle, prolonging the life of red blood cell so it can increase the gap between transfusions, in some intermedias, it increases the Hb
Zinc:Most of the metabolic reactions depend on the presence of zinc. They can have three roles either thy help in formation of enzymes, or they themselves are the main components of proteins or they can regulate certain body functions. Very important for growth that its absence may cause growth retardation to children
Ayesha, i tried to be brief but you can learn more about the above in this link
http://lpi.oregonstate.edu/infocenter/vitamins.htmlAlso in my opinion, i think that if there is a possibility to check these levels in the body would be the best choice because sometimes things contradictes with other .
For example too much zinc decreases the absorption of magnesium and chelates copper
Hope this helps
manal