Re: Are certain types of Magnesium useless to take?
Magnesium oxide is effectively useless by the body. Any chelated magnesium is good, such as orotate, glycinate, taurate, and citrate. Citrate, for your money, is probably the most practical. For every 500 mg of magnesium citrate, there are approximately 75 mg of magnesium ions. It is absorbed with or without food, but empty stomach seems to work best for citrate salts. Inorganic forms, such as magnesium oxide, and carbonate, aren't readily absorbed. If you buy a powder, such as magnesium chloride/citric acid powder, absorbs pretty well. I would stay away from magnesium aspartate because the compound is also aspartic acid, which probably isn't all that good for you. The oil that was mentioned above is in fact very good, as that is usually magnesium chloride which can absorb through the skin if you rub it on. Magnesium malate is also available, and absorbs very well.
When you buy magnesium, it will tell you how much of the salt is present in each capsule, which does not translate directly to how much actual magnesium. A good rule of thumb is that for every 500 mg salt, you will obtain anywhere from 30-75 mg of actual magnesium.
Yes you are right, magnsium deficiency is pretty common as there isn't much of it in the diet.