What is Mg (Magnesium) plus protein?

Magnesium Plus Protein: Understanding the Relationship

Magnesium plus protein refers to the physiological relationship between magnesium and protein in the body, where approximately 25% of serum magnesium is bound to albumin and 8% to globulins, creating an important mineral-protein complex essential for proper bodily function. 1

Physiological Relationship Between Magnesium and Protein

Magnesium is the fourth most abundant mineral in the body and the second most abundant intracellular cation. In blood, about 1/3 of magnesium is attached to plasma proteins while the remaining 2/3 is filtrated by the kidney 2. This relationship is critical because:

• Magnesium is essential for the activity of magnesium-dependent adenyl-cyclase involved in both parathyroid hormone (PTH) release and activity on bone
• In magnesium deficiency, there is both deficient PTH release and peripheral resistance to PTH, which can lead to hypocalcemia 2
• Protein retention and magnesium metabolism are interconnected, particularly in growing individuals and those with high protein intake

Clinical Implications of Magnesium-Protein Interaction

Impact of Protein Intake on Magnesium Status

Research has demonstrated important relationships between protein intake and magnesium metabolism:

• High protein intake can affect apparent magnesium absorption (ingested magnesium minus fecal magnesium) 3
• While high protein intake appears to enhance apparent magnesium absorption, true magnesium absorption remains unaffected 3
• A moderate increase in dietary protein (from 65g to 94g) can slightly increase urinary magnesium excretion 4
• In growing individuals, high protein intake may decrease urinary magnesium concentration due to increased urine volume and reduced excretion of urinary magnesium 5

Clinical Management of Magnesium Deficiency

For patients with magnesium deficiency, particularly those with short bowel syndrome or other malabsorptive conditions:

• Oral magnesium supplementation is the first-line treatment for mild-to-moderate deficiency
• Magnesium oxide is commonly given as gelatine capsules of 4 mmol (160 mg) to a total of 12-24 mmol daily 2
• Magnesium oxide is usually administered at night when intestinal transit is assumed to be slowest, allowing more time for absorption 2
• For severe deficiency or when oral supplementation is not tolerated, intravenous magnesium may be required 6

Special Considerations for Different Patient Populations

Short Bowel Syndrome Patients

Patients with short bowel syndrome have specific considerations:

• Hypomagnesemia is common and rehydration to correct secondary hyperaldosteronism is the most important first step 2
• Most magnesium salts are poorly absorbed and may worsen diarrhoea/stomal output 2
• If oral magnesium supplements do not normalize magnesium levels, oral 1-alpha hydroxy-cholecalciferol in gradually increasing doses may improve magnesium balance 2

Parenteral Nutrition Considerations

For patients requiring parenteral nutrition:

• Magnesium may be provided using magnesium sulfate rather than magnesium chloride, as the latter increases the anion gap and risk of metabolic acidosis 2
• In preterm infants exposed to maternal magnesium therapy, magnesium intakes must be limited and adapted to postnatal blood concentrations 2
• The adequacy of calcium and phosphorus intakes can be adjusted until both are excreted simultaneously with low urine concentrations (>1 mmol/L) 2

Monitoring and Follow-up

When managing patients with magnesium deficiency:

• Monitor serum magnesium levels until normalized 6
• In patients with renal impairment, careful monitoring is required to avoid hypermagnesemia 6
• When supplementing with magnesium, consider concurrent monitoring of calcium and phosphorus levels due to their interrelated metabolism 2
• For patients with fatigue potentially related to magnesium deficiency, assess improvement in symptoms following supplementation 6

Common Pitfalls and Caveats

• Total blood magnesium concentration is not the best estimate of the biologically active fraction (ionized magnesium); red blood cell magnesium concentration (around 2.5 mmol/L) may better indicate tissue magnesium content 2
• When using magnesium supplements, be aware that different forms have varying bioavailability - magnesium glycinate is one available form 7
• Always address underlying causes of magnesium deficiency, such as treating inflammatory bowel disease if present, correcting other electrolyte imbalances, and modifying medications that may deplete magnesium 6
• When supplementing zinc along with magnesium, maintain appropriate ratios to avoid imbalances 6

Understanding the relationship between magnesium and protein is essential for proper clinical management of patients with magnesium deficiencies, especially those with conditions affecting protein metabolism or absorption.