I was just at my pharmacy talking to the pharmacist about potassium. Reason being that I get muscle soreness and cramping mainly in my hamstrings and calfs after bjj. I don't care for bananas really and my multi vitamin only contains like 2% daily values. Any way he was telling me that I should also consider supplimenting magnesium. He says anyone who who lifts weights or engages in strenuous excercise could benifit. Helps with overall muscle health, size and definition, creatine and protein synthesis etc. Also he said tha multi vitamins contain only a minimum amount of magnesium. I thought this was interesting so I am passing it along. Here is a link to an article I found regarding the benefits of magnesium:
http://www.thinkmuscle.com/articles/.../magnesium.htm