Although magnesium is vital for human health, it is estimated that half of all adults are magnesium deficient.

Magnesium is the fourth most abundant mineral in the human body and essential in about 80 per cent of known metabolic functions, including as a cofactor for more than 300 enzyme reactions. It has been estimated that 60 per cent of adults in the West do not consume the average daily intake recommended and that over 45 per cent of adults are magnesium deficient.

Magnesium deficiency

Early signs of a magnesium deficiency are non-specific and include loss of appetite, lethargy, nausea, vomiting, fatigue and weakness. Pronounced magnesium deficiency presents with symptoms of increased neuromuscular excitability such as tremor, spasms, muscle cramps, tetany and generalised seizures. Severe deficiencies can cause cardiac arrhythmias including atrial and ventricular tachycardia.

Cardiovascular disease

Magnesium plays a critical role in blood pressure regulation. A meta-analysis was conducted of magnesium supplementation and blood pressure showing supplementation, even at low doses (240mg/day) could be effective in lowering the blood pressure of hypertensive patients while they were on antihypertensive medications. In hypertensive patients on no medication, a higher dose (500mg/day) was needed to lower blood pressure.

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In studies on patients with coronary heart disease, those with higher serum magnesium levels had significantly fewer symptoms of arrhythmias or angina, thus reducing their risk of heart attacks. Dietary magnesium supplementation has been shown to be inversely correlated with coronary heart disease.

Metabolic syndrome and diabetes

Magnesium depletion has been associated with various types of diabetes, being reported in up to 47 per cent of individuals with Type 2 diabetes.

One study of 63 patients with diabetes showed that taking a supplement of magnesium for six weeks improved measures of insulin sensitivity and glycaemic control compared to placebo.

Neurological disorders

Magnesium has shown promise in reducing the symptoms of insomnia, anxiety (including panic attacks) and depression.

Headaches

Several trials were conducted in patients with migraine headaches, showing that high-dose magnesium reduced attacks and associated symptoms, and prevented recurrence in nearly 90 per cent of patients.

Gastrointestinal system

Magnesium has been used clinically to reduce the symptoms of dyspepsia, a key symptom in gastroesophageal reflux disease (GERD), and in the relief of constipation.

Pre-eclampsia in pregnancy

Pre-eclampsia is defined as high blood pressure, severe ankle swelling (fluid buildup) and protein in the urine during pregnancy and often occurs with seizures. Magnesium is used in obstetric care for the prevention of seizures in pregnant women with pre-eclampsia. Compared with the anticonvulsant phenytoin, magnesium sulphate was the treatment of choice. Research also supports a role for magnesium in preventing brain damage in premature infants.

Asthma

Patients with asthma have a higher incidence of magnesium deficiency than individuals without asthma. Magnesium has been shown to promote bronchodilation, and children and adults alike have shown improved lung function and a reduction in hospital admissions when administered.

The use of magnesium in a nebuliser has also been investigated and shown that inhaled magnesium sulphate was effective in patients with acute asthma.

Osteoporosis

Sixty per cent of magnesium is located in human bones, where it plays a central role in skeletal development. A magnesium deficiency adversely affects vitamin D metabolism and calcium homoeostasis and therefore the increases the risk of osteoporosis. Many pharmaceutical medications to treat osteoporosis reduce magnesium. High vitamin D supplementation can also exacerbate a magnesium deficiency.

Studies have shown that megadosing with calcium in postmenopausal women showed no significant effect on bone mineral density but increased the serious risk of soft tissue calcification. However, when supplementing with magnesium, a significant increase in bone mineral density was observed within one year.

Food sources

Dark green leafy vegetables, nuts (brazil nuts are the highest source), green foods (magnesium is part of the chlorophyll molecule), avocado, whole grains and some legumes. Magnesium bicarbonate (alkaline) drinking water is a good supplement.

Supplements

The chelated form of magnesium appears to be more useful as it increases the physiologically active form of magnesium in the body.

There has been considerable research in the last few years on the transdermal applications of magnesium. These can be effective as they bypass the digestive system and are absorbed straight into the site.

Interactions with other nutrients

High doses of zinc and low-protein diets and large increases of dietary fibre may interfere with magnesium absorption.

Magnesium toxicity

While a deficiency of magnesium is common, an overdose of magnesium is also possible — called hypermagnesia — common in people with functional constipation that have been taking high doses of magnesium oxide for lengthy periods of time. Magnesium toxicities only occur with supplemental magnesium, not with foods.

The most common symptom of an overdose is diarrhoea, as magnesium has a laxative effect (as in Epsom salts). If this continues, symptoms develop such as muscle weakness, difficulty breathing, lethargy, confusion, disturbances in cardiac rhythm and deterioration of kidney function and severe hypotension. A severe toxicity may result in cardiac arrest.

Drug interactions

Magnesium may interfere with pharmaceuticals such as digoxin, some antibiotics and anti-malarial medications, and the bisphosphonates used to treat osteoporosis (avoided by taking 2 hours apart).

Long-term use of proton pump inhibitors (for reflux) and diuretic medications may increase the risk of magnesium depletion.

Contraindications

Magnesium supplementation is not recommended with kidney diseases (due to low creatinine clearance) unless closely monitored, as supplementation can lead to hypermagnesia.