Magnesium is an essential macromineral needed in gram amounts per day in the human diet. However, evidence suggests that the Western diet is devoid of foods that contain magnesium and as a result, many individuals in developed nations do not obtain enough magnesium in their diet. Magnesium is present in some cereal grains, and also in green leafy vegetables. Supplements of magnesium are also available and are effective and cheap. Magnesium is well absorbed in humans and once in circulation forms magnesium ions that play a diverse role in human physiology. In particular, magnesium ions are required for correct bone formation, as cofactors in enzymes and as ions in nerve impulses. One role for magnesium that has been particularly well studied is its role in the maintenance of correct heart health. In this respect, mammals require magnesium to maintain a number of parameters of heart health, and low magnesium diets may increase the risk of ischaemic heart failure considerably.
Magnesium loss from the myocardium is one of the earliest clinical changes that is observed in experimental animals and humans in cardiomyopathy, suggesting that magnesium intake is pivotal in maintaining correct heart function. For example, low magnesium levels are found in the heart tissue of patients who have undergone myocardial infarction. The loss of magnesium may equate to around one third of the total magnesium content of the heart. The magnesium content of the infarcted portion of the heart is lower than other non-affected parts of the heart. However, skeletal muscle tissue is not lower in myocardial patients compared to healthy controls, suggesting that the magnesium loss from muscle is heart specific. Analysis of the plasma of subjects admitted to hospital after suffering myocardial infarction shows that they have significantly lowered levels of magnesium compared to healthy controls. Magnesium loss from the heart tissue may therefore be a result of or a cause of myocardial infarction.
Administration of magnesium salts to mammals has been observed to reduce the hypoxic damage that results from myocardial infarction. Intravenous magnesium also reduces the tachycardia, fibrillation and ectopic rhythm associated with myocardial infarction. Human studies have reported benefits in terms of clinical symptoms and survival in subjects administered intravenous magnesium following myocardial infarction. This may relate to the ability of magnesium ions to dilate the coronary arteries and increase blood flow to the heart, thus reducing the effects of hypoxia. The benefits of magnesium may explain the reduced risk of myocardial infarction in area with hard drinking water. A higher incidence of ischaemic heart disease is also reported in whites compared to blacks, the latter being observed to have higher magnesium blood levels than the former. The muscle relaxing properties of magnesium may therefore be cardioprotective, especially where a magnesium deficient diets exist.
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