A deficiency of any mineral that ends in -ium can cause leg cramps (potassium, calcium, magnesium, etc.). A sodium deficiency is possible, but not likely with a standard American diet. Some people don't absorb over-processed table salt well, though, so it's worthwhile to switch to gray Celtic sea salt and eat more vegetables natually high in sodium.
Taking supplements can help, but they should be high quality supplements, and you should do research to see if that certain nutrient needs to be taken with another vitamin or mineral to be absorbed well. Nutrients from food sources absorbed more easily and a better place to start. If you find that eating plenty of dairy, bananas, and OJ doesn't work, it's a good idea to consult a nutritionist who can point you in the right direction.