Your coaches lie to you.
you do not require any supplement just because all supplement you take comes in your food. if the caloric requirement is more, the increase of it (calories & proteins. fruits & vegetables) in a balanced way assures a adequate intake of all the nutrients. renowned researchers in exercise physiology & nutrition sciences (Katch & Mcardle) refute the idea of taking supplements in training.
More to it you can not assess the deficiency of particular nutrient (that you take as supplement) in common laboratory conditions. Toxic levels too occur with high intakes. However generally the nutrient requirement is in a vary wide range. That means one can tolerate increased nutrients as supplements in a wide range which does not mean that we require it more than a adequate level. More than adequate range do not also mean a high training output or competitive result or augmented health.
Following are self-explanatory terms associated with nutrient requirements.
Please note the following
• EAR: Estimated Average Requirements
• RDI: Reference Daily Intake (Please refer to ICMR guideline, 1991- NIN, Hyderabad)
• AI: Adequate Intake
• UL: Tolerable upper intake levels