An important consideration in measuring blood magnesium is that it is levels of ionized magnesium that really matter. I learned this in our equine neonatal ICU unit from a very bright resident.

More recently, my daughter had to spend three weeks in ICU and eventually she developed severe cramping and leg contracture. Fortunately, total serum magnesium was a bit low and they infused her with magnesium intravenously. That had a remarkable effect on relaxing her muscles and allowing us to work on straightening her legs. Subsequently, although she had recurring issues with leg muscle contractions, her serum total magnesium was “normal”, and they would not infuse her with more magnesium. I had some pointed discussions with the attending physician, who ultimately agreed to order more magnesium infusions.

By the way, excessive dietary magnesium can promote kidney stones in some people. Dietary magnesium is poorly absorbed (thus its laxative effect), so a balanced diet that includes the foods you mention is probably the best approach, rather than trying to use diet to push magnesium levels.