Magnesium (Mg)

Function

Magnesium is a mineral naturally found in your body and the food you consume daily. It is responsible for many processes within the body that include but are not limited to protein synthesis, bone formation, blood pressure regulation, nerve function, and electrical conduction in the heart.

Magnesium serves as a co-factor for over 300 biochemical reactions within the body. Magnesium's importance is in protein synthesis, nerve and muscle functioning, bone growth, blood pressure and glucose regulation, and normal cardiac rhythm. An average adult has approximately 22 to 26 grams of magnesium. Approximately 60% of the total is stored in bone, 39% is stored intracellularly, and only 1% is found in blood vessels' free or ionized active form. Magnesium is also involved in sodium, potassium, and calcium channels. Magnesium homeostasis depends on kidney and small bowel function and storage in bone and cells.

Deficiency

Magnesium (Mg) deficiency is associated with many common chronic conditions and potentially severe health care outcomes, including cardiovascular disease, cardiovascular risk factors, and diabetes. However, Mg deficiency is underdiagnosed and often underrecognized in the ambulatory health care setting.

Currently, approximately 60% of adults have an inadequate dietary intake of Mg due to common modern food processing and dietary practices, medications, and modern farming and cultivation techniques. Signs and symptoms of Mg deficiency are numerous, nonspecific, and widespread.

Toxicity

Magnesium toxicity is commonly caused by the overuse of magnesium-containing medication or the under-excretion of magnesium by the kidneys. Early recognition, as well as a high index of suspicion, is critical when diagnosing magnesium toxicity before the onset of fatal complications such as hypotension, respiratory paralysis, and cardiac arrest.

Magnesium is excreted in the kidneys, so those with chronic kidney disease are particularly at risk. However, magnesium excretion is only impaired when the creatinine clearance falls below 30 ml/minute. Patients on dialysis can also experience a quick rise in magnesium levels if their treatments are missed. Additionally, the magnesium concentration in cells is much higher than in plasma. Therefore, patients undergoing cancer treatment who have high rates of cellular hemolysis are also at risk. Lastly, women receiving preeclampsia treatment are also at risk for magnesium toxicity due to the high dosage needed to prevent

seizures. Identifying the causes of magnesium toxicity, whether through over-absorption or under-secretion, is vital to identify patients at risk for magnesium toxicity and prevent future toxicities.

Diagnosis:

Generally, serum magnesium is utilized to determine the Magnesium status of a patient. However, serum magnesium reflects the extracellular magnesium. Research indicates that the location of magnesium is predominantly intracellular, and that three fractions are present in the blood: free ionized (60%–70%), protein bound (20%–30%) and complexed with anions (5%–10%). Total magnesium body store averages 25 g. It is distributed among bone (50%), muscles (27%), soft tissues (19%), erythrocytes (0.5%) and serum (0.3%). Serum levels represent a negligible percentage of the total amount found in the body and cannot be regarded as a reliable biomarker of total magnesium status.

Whole blood levels represent intra- and extracellular levels. Urine shows how much is excreted. Hair and other body tissue indicate body storage.

References:

• Silverio Rotondi, Sandro Mazzaferro, Magnesium: extracellular, intracellular or total magnesium status?, Nephrology Dialysis Transplantation, Volume 38, Issue 6, June 2023, Pages 1349–1351
• Fiorentini D, Cappadone C, Farruggia G, Prata C. Magnesium: Biochemistry, Nutrition, Detection, and Social Impact of Diseases Linked to Its Deficiency. Nutrients. 2021 Mar 30;13(4):1136.