Magnesium status has a direct effect upon the relaxation capability of vascular smooth muscle cells and the regulation of the cellular placement of other cations important to blood pressure – cellular sodium:potassium (Na:K) ratio and intracellular calcium (iCa(2+)). As a result, nutritional magnesium has both direct and indirect impacts on the regulation of blood pressure and therefore on the occurrence of hypertension. Hypertension occurs when cellular Na:K ratios become too high, a consequence of a high sodium, low potassium diet or, indirectly, through a magnesium deficient state which causes a pseudo potassium deficit. Like wise, magnesium deficiency alters calcium metabolism, creating high iCa(2+), low serum calcium and low urinary calcium states even when calcium intake is adequate. High iCa(2 + ) and high cellular Na:K ratio both occur when cellular magnesium becomes too low and the Mg-ATP driven sodium-potassium pump and calcium pump become functionally impaired. High iCa(2+) has several vasoconstrictive effects which lead to hypertension, an indirect result of low magnesium status. Dietary calcium is directly proportional to dietary magnesium. Serum magnesium does not reflect true magnesium status as do intracellular magnesium measurements. Several studies on the effect of calcium on blood pressure need these added considerations of magnesium status to fully understand the impact of the Mg:Ca ratio as the primary cause of hypertension and other aspects of Syndrome X. Magnesium supplementation above 15 mmol per day are required to normalize high blood pressure in unmedicated hypertensive patients while 15 mmol per day will lower high blood pressure in patients treated with anti-hypertensive medications. In most humans, healthy blood pressure depends upon a balance of both Na:K and Mg:Ca ratios at both cellular and whole body levels which, in turn, require adequate, long-term intakes of nutritional magnesium. The knowledge that low magnesium causes imbalance in both cellular and physiological calcium widens our view of the studies showing hypertensives have abnormal calcium metabolism.
Clin Calcium 2005 Feb;15(2):255-60