Magnesium is an essential mineral in our body, and is used in protein synthesis, membrane integrity, nervous tissue conductivity, neuromuscular excitability, muscle contraction, hormone secretion and intermediary metabolism. But what is magnesium and why do we need it?
Magnesium is an abundant cation in the body and is involved in over 300 enzymatic reactions, such as the metabolism of macronutrients (carbohydrates, protein, and fats), nucleic acids, the synthesis of hydrogen transporters, and in all energy metabolism reactions involving ATP (adenosine triphosphate) (1). Magnesium works with calcium in the muscles to help with muscle contraction and relaxation. The adult body contains approximately 21-28 g of Mg (1,2).
Magnesium deficiency is frequently observed in chronic alcoholics, diabetic patients, some cardiovascular diseases, pre-eclampsia and eclampsia during pregnancy and birth, and sickle cell disease (1,2). It is usually related to either deficiency or depletion of magnesium from many factors, such as intestinal malabsorption, diarrhoea, malnutrition (3), urinary losses (increased urine production and excretion), sweat losses or reduced magnesium bone uptake (2). Signs of deficiency may include changes in bone and mineral metabolism (hypokalemia, osteoporosis), neuromuscular functioning (seizures, vertigo, muscle weakness, tremor, depression), or cardiovascular function (cardiac arrhythmia, myocardial ischemia, hypertension, vascular disease) (3).
Several studies have shown that among patients with diabetes the frequency of hypomagnesia (low magnesium levels) is higher than expected, and it is correlated with the degree of severity of hyperglycemia (1). Supplementing with magnesium chloride restores serum magnesium levels, improving insulin sensitivity and metabolic control in type 2 diabetic patients with decreased serum levels (4,5). In previous research magnesium did not appear to be an independent risk factor for developing diabetes (6), however more recently a prospective research investigation into type-2 diabetes development and magnesium intake did show a positive relationship (7,8). The mechanism for why this happens is unclear, but evidence indicates a link between low magnesium and a reduction of tyrosine-kinase enzyme activity at the insulin receptor level, which may result in the impairment of insulin action and development of insulin resistance (9).
Many studies indicate that athletes may be deficient in magnesium. Two main reasons for this may be that they commonly consume diets with inadequate mineral amounts (lower than the RDA), and their mineral losses in urine and sweat are higher (2,10,11).
The richest sources of dietary magnesium include whole seeds, unmilled grains, green leafy vegetables, legumes and nuts. Fibre, phytates, alcohol or an excess of phosphate and calcium may reduce the absorption of magnesium. The recommended daily intake based for healthy adults aged 19 – 30 years is about 310 mg daily for women and 400 mg daily for men (12).
Spinach (1 cup cooked = 157 mg)
Pumpkin seeds dried (2 Tbsp. = 156 mg)
Lima beans (1 cup cooked = 126 mg)
Tuna (180 g = 109 mg)
Brown rice (1 cup cooked = 86 mg).
So eat up your greens.