If you want your body to function at maximum potential, you need magnesium in your system. This amazing and healthy mineral is responsible for over 300 metabolic functions in the human body, and every single cell needs it to function properly. The thing is, research shows that nearly half of Americans are magnesium deficient, which can cause a myriad of problems from chronic fatigue and depression to leg cramps and heart disease. To get a gage on whether or not you have enough magnesium in your system, keep a look out for these early warning signs.