Vitamin C in extended release tablets    The human immune system is attacked daily by various viruses, diseases, fatigue, stress, few hours of sleep and poor nutrition. The fact that the Mediterranean diet is rich in citrus fruits does not exclude the fact that there is an increased need to take vitamin C in addition, to strengthen the body's defenses.    Vitamin C According to Official Health Claims:    contributes to maintaining the normal function of the immune system during and after intense physical exercise  contributes to the normal formation of collagen for the normal functioning of blood vessels