Most Americans don’t consume the recommended daily amount of magnesium, which is 320 mg a day for women, and 420 mg for men.

Older people often have low magnesium levels because they tend to consume and absorb less of the mineral.

But because there’s no good way to measure total magnesium in the body, it’s hard to know exactly how many people are truly deficient.

I recommend taking 300 to 500 mg of magnesium every day as a supplement to guard against magnesium deficiency.

Magnesium can be hard on the kidneys, so be careful if you have kidney problems. It can also sometimes interact with other medications.

If you have any concerns, discuss them with your doctor.

Magnesium deficiency is often discussed in terms of nutritional shortcomings, but in 2011, scientists discovered a genetic cause.

Researchers found that changes in a gene called CNNM affects a protein that is anchored in the membrane of kidney cells and intestinal cells; this gene is responsible for the absorption of magnesium in the bloodstream.

Because this process no longer works in the defective protein, magnesium is not put into the bloodstream but excreted through the intestine and the urine, and carried out of the body.