Cofactor in more than 300 enzyme systems; energy, protein/DNA, nerves, muscle, glucose, blood pressure and bone.
Switzerland age 18–65: 300 mg/day women, 350 mg/day men.
Pumpkin seeds, almonds, legumes, whole grains, spinach, cocoa and mineral-rich water.
Early loss of appetite, nausea, fatigue and weakness; severe deficiency causes tingling, muscle cramps, seizures and arrhythmias.
Severe deficiency can also lower potassium and calcium. Common nonspecific cramps do not prove magnesium deficiency.
Hair and nails do not reliably indicate magnesium deficiency.
Gastrointestinal losses, alcohol dependence, poorly controlled diabetes, diuretics, proton-pump inhibitors and older age.
Review diet, medicines and losses. Serum magnesium can be normal despite low body stores and needs clinical interpretation.
Food first. Target supplementation for inadequate intake, losses or confirmed deficiency; consider kidney function and medicines.
Supplements commonly cause diarrhoea; kidney failure can lead to dangerously high levels.