GO MAGNESIUM 1-A-DAY is a high strength,1-A-Day formula which contains 500mg of elemental Magnesium per capsule. Sourced from seawater, this natural marine Magnesium contains no Magnesium oxide, giving it superior absorption as well as being gentle on the digestive tract. Magnesium is effective in supporting relaxation, soothing muscle tension and muscle tightness as well as for supporting a good nights sleep.