A few years ago, the US Department of Agriculture determined that two out of three Americans didn’t meet the average daily intake requirement for magnesium, the fourth-most-abundant mineral in our cells. Our bodies need magnesium for energy production…fat and protein synthesis…muscle relaxation…and much more. Magnesium-rich foods include green vegetables such as spinach and dark-leaf lettuce, but most people don’t get enough magnesium from their diets. Your doctor can check your magnesium level—and help you determine how much you need to supplement.