What are the benefits or negatives of taking magnesium powder (2 tablespoons) a day with water? is there any harm i should worry about?

Many benefits: Magnesium deficiency is extremely common. Symptoms include muscle tension/spasms, fatigue, anxiety, insomnia, constipation and headaches. One can not overdose unless you have kidney failure. The only side effect is diarrhea if you choose a form that is poorly absorbed. Magnesium glycinate, taurate and citrate are well-absorbed. See http://drcarolyndean.com/magnesium_miracle/