Does magnesium really protect you against heart attacks?

Dr. Frank Shallenberger, MD

October 4, 2021


You have probably heard that taking magnesium supplements is an effective way to decrease your risk of a heart attack. But is it true?

Not all the studies agree. So what’s the truth? And what should you do about it?

The reason many of the studies can’t come to the same conclusion is because there isn’t a good way to measure how much magnesium is actually in your body. The blood levels of magnesium don’t fall below normal until a deficiency is severe. So they are not helpful.

How can you figure out if you need more magnesium?

Just taking some magnesium “for insurance” is one way of doing it. But how can you be sure that you are taking enough and that you are absorbing what you take?

There’s a Better Way to Measure

A new study is giving us what may be the best way to measure magnesium. Additionally, it is giving us an idea of what the optimal levels are. And, finally, it is showing how powerful magnesium is in preventing heart attacks.

The researchers looked at 7,664 men and women, all of whom were free of heart disease. They measured their blood levels of magnesium. But they also had them collect their urine for 24 hours and then measured the amount of magnesium that they eliminated in their urine.

The rationale was that unlike blood levels, the amount of magnesium that is in the urine has to take into account the amount that they took and the amount that they absorbed.

Ten years later, 462 of them had suffered a heart attack. The researchers then analyzed the chance of having a heart attack as it related to the levels of magnesium initially found in their urine.

They found that the men who had urine magnesium levels less than 2.93 mmol/24h and the women whose levels were less than 2.45 mmol/24h had a 60-100% greater chance of having a heart attack than the men whose levels were greater than 5.24 and the women whose levels were greater than 4.38.

What About the Blood Levels of Magnesium?

They were not in any way predictive of who was at risk. So if you have already had a heart attack, or if you are at risk for one, have your doctor analyze your 24-hour urine for magnesium.

Make sure that you are taking enough magnesium to get your levels over 5.24 mmol/24h for men and 4.38 mmol/24h for women. I think the best form is magnesium citrate because it is so bioavailable. Take in the order of 300 to 1,000 mg per day.

Magnesium can cause loose stools if you take more than your bowels can handle. So if that happens, back off on the dose to an acceptable level.


Joosten, M.M., R.T. Gansevoort, and K.J. Mukamal. “Urinary and plasma magnesium and risk of ischemic heart disease.” Am J Clin Nutr, 2013 June;97(6):1299-306.


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