Sources:
Green leafy vegetables, legumes, nuts, seeds, whole grains, medicines (e.g., Milk of Magnesia), Epsom salt. Over the last 60 years, the Mg content in fruits and vegetables has decreased by 20-30%,and 80-90% of Mg is lost during food processing.
Absorption factors:
The intestine, bone and kidney maintain magnesium homeostasis. Unlike other minerals, Mg can be absorbed along the entire length of the GI tract. Soft drinks, low protein diets, foods containing phytates, polyphenols and oxalic acid, fluoride, antibiotics, and oral contraceptives bind to magnesium and produce insoluble precipitatesor complexes, negatively impacting Mg availability and absorption. Caffeine, alcohol and diuretics (e.g., furosemide, bumetanide) increase renal excretion of Mg. Antacids (e.g., omeprazole) affect Mg absorption due to the increase in GI pH.
Biochemical reactions:
Mg plays a role in hundredsofenzymatic reactions involved in hormone receptor binding, muscle contraction, neural activity, neurotransmitter release, vasomotor tone, blood glucose control,mitochondrial energy production, and cardiac excitability.
RBC magnesium is often cited as preferable to serum and plasma levels due to their higher magnesium content (0.5% vs 0.3%). Serum is used to assess hyper-or hypomagnesemia. Urinary Mg may not correlate with Mg status in the body due to the variable degree of renal reabsorption and secretion. Variables affecting this include dietary intake, existing Mg status, mobilization from bone and muscle, hormones (estrogen, parathyroid, calcitonin, glucagon), medications (diuretics, chemotherapy), diabetes. Anywhere between 5% to 70% of filtered Mg may be excreted in the urine.24-hour urine levels may be more reliable than spot urine. Normal or high urinary excretion is thought to indicate renal Mg wasting, whereas low Mg excretion suggests reduced intestinal absorption.
Magnesium
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