Contrex is a natural mineral water that has no calories. Each eight ounce serving of Contrex delivers 10% of the Reference Daily Intake (RDI) for Calcium and 4% of the RDI for magnesium. Contrex is an ideal beverage for health conscious women who are minding their calories and trying to achieve their ideal shape because it helps them get the calcium they may be lacking. Without calcium, women may experience deterioration in their bone mass.