Magnesium - The Hidden Deficiency

Despite the vital importance of magnesium, in today’s healthcare setting there is no great way to test for magnesium deficiency. Even when labs are ordered to determine someone’s magnesium level, these tests rarely reflect true magnesium deficiency.

The most common lab test ordered to check magnesium status is the blood serum magnesium level. This level is tightly controlled by your body because it is so important in the function of your organs. This test can be abnormal in acutely ill hospitalized patients. However, the serum magnesium level does not reflect the intracellular magnesium level. Less than 1% of the total magnesium in your system is located in your blood serum. A normal blood serum level doesn’t give any insight into the other 99% of magnesium stores in your system. In order for this level to be low in otherwise healthy individuals, they would have to be so magnesium deficient that their body is unable to pull any magnesium from other body tissues to regulate the all-important serum magnesium level.

Red blood cell (RBC) magnesium tests have become more popular in recent years. The theory is that red blood cells have slightly higher levels of magnesium and that they might be able to identify magnesium deficiency more accurately than a serum magnesium level. However, there are no clinical studies to demonstrate that RBC magnesium tests are accurate or reliable in detecting magnesium deficiency. 

A study published in the British Medical Journal Open Heart identified three reliable ways to test for magnesium deficiency. The first is the retention of magnesium load test. To complete this test, magnesium is given through an IV and then the patient’s urine is collected for a 24 hour period. A lower than normal amount of magnesium excreted in the urine indicates systemic low magnesium levels. The second reliable test to detect magnesium deficiency is via a muscle biopsy. This involves the removal of muscle tissue through an incision or biopsy needle to test the tissue sample for it’s magnesium content. The third viable option is a mononuclear cell magnesium level. For this test, mononuclear cells are separated from whole blood samples. This  is difficult to perform and is not available in typical clinic or hospital laboratories. Not surprisingly, due to the invasive and cumbersome nature of these tests, they are rarely ordered.

Magnesium is an important co-factor in over 300 chemical reactions in the human body. It is essential for healthy nerve and muscle function. Magnesium plays a role in blood pressure regulation, and contributes to the healthy development of DNA, RNA, and the powerful antioxidant glutathione. Studies have demonstrated that diets higher in magnesium are associated with a reduced risk of diabetes, osteoporosis, and ischemic stroke. Unfortunately, in the modern world, our diets rarely supply an adequate amount of magnesium. However, magnesium supplementation can supply what our diets lack.

There are a number of different forms of magnesium supplementation to choose from. It’s easy to get lost in the choices. Different forms of magnesium may have different advantages depending on your situation. However, the most important factor to consider is whether or not your body can absorb the magnesium supplement. If you can’t absorb magnesium, your body can’t utilize it. A study looking at the bioavailability of magnesium concluded that magnesium citrate, chloride, glycinate, glucinate, and fumirate all have good bioavailability when taken orally. On the other hand, magnesium carbonate was shown to have poor oral bioavailability.

The National Institutes of health (NIH) recommends a daily intake of magnesium between 310mg and 420mg for healthy adults, depending on age and gender. In healthy adults, excess magnesium is typically excreted by the kidneys into the urine.

Despite the importance of magnesium, there is not an easily accessible, widely accepted test for magnesium deficiency. Due to this, it’s important to know that you likely won’t ever be told by a healthcare professional that you have a low magnesium level.  Yet deficiency of this mineral is common. Magnesium is vital to the function of the human body and magnesium deficiency is implicated in a variety of chronic diseases. In the modern world where we rarely get enough magnesium from our diet, it’s important to consider magnesium supplementation.