Somehow, I ran out of my supply of magnesium tablets and recently made a note to order more. I do take a multi-vitamin with minerals, but that gives me only 125 mg of magnesium each day.

This is well below the official U.S. and Canadian recommendations for daily intake of magnesium. For a man of my age I should be getting 420 mg, although no more than 350 mg should come from supplements.

Those of us who have diabetes are often deficient in magnesium. Several studies have suggested that taking a...