Mineral

• UK RNI 300 mg
• US RDA 350 mg

Functions

• Anti-diabetic: release of insulin, maintenance of pancreatic insulin production cells, and maintenance of affinity and number of insulin receptors
• Balance and control of calcium, potassium and sodium ions
• Bone development (more than 60 per cent is found in bone)
• Calcium balance
• Can substitute for manganese in many instances
• Co-factor for vitamins B1 and B6
• Energy production
• Methionine metabolism
• Muscle contraction and relaxation
• Nerve impulse transmission
• Protein synthesis, growth and repair

Good food sources

• Bitter chocolate
• Leafy green vegetables
• Nuts and seeds
• Soya beans
• Whole grains (particularly oats)

Deficiency signs and symptoms

• Anaemia
• Anorexia
• Back pain (some types)
• Chronic fatigue
• Chronic muscle pains
• Convulsions and epileptic fits
• Difficulty in relaxing muscles
• Difficulty swallowing
• Flickering eyelids and facial tics
• Fluid retention
• High or low blood pressure
• Hyperactivity in children
• Hypoglycaemia
• Increased risk of heart attack
• Insomnia
• Irregular heartbeats
• Kidney stones
• Late-onset diabetes
• Loss of bone density
• Muscle jerks and spasms
• Muscle weakness and tremors
• Nervousness and anxiety
• Palpitations
• Period pains
• Poor circulation
• Potassium depletion
• Premenstrual syndrome
• Reduced ability to detoxify
• Sodium accumulation inside cells
• Tendency to 'startle' too easily

Preventing deficiency

On testing for nutritional deficiencies, doctors in the UK find magnesium (and zinc) deficiency more frequently than any other minerals. The diet of many people is low in magnesium-rich foods. In addition a diet high in calcium and phosphorus can render magnesium less bioavailable and thus aggravate a potential deficiency. Wholemeal flour contains three times as much magnesium as white flour, therefore this and other whole grains such as oatmeal should be regularly consumed, along with nuts, sesame seeds and dark green leafy vegetables, preferably on a daily basis.

Coffee consumption has been associated with the increased excretion of magnesium and other minerals. Magnesium status can be compromised by chronic diarrhoea, over-use of enemas or laxatives, and by the contraceptive pill. Magnesium also be severely depleted by stress and strenuous exercise. Dietary imbalances such as a high intake of fat and/or calcium can intensify magnesium inadequacy, say one group of researchers, especially under conditions of stress. Low magnesium status increases the release of stress hormones which in turn depletes tissue magnesium levels. These hormones also stimulate the liberation of fatty acids, which then complex with magnesium, reducing its bioavailability. Thus, say the researchers, all stress, whether exertion, heat, cold, trauma, pain, anxiety, excitement or even asthma attacks, increases the need for magnesium. (Seelig MS: Consequences of magnesium deficiency on the enhancement of stress reactions; preventive and therapeutic implications [a review]. J Am Coll Nutr 13(5):429-46, 1994.) Also Casoni I et al.: Changes of magnesium concentration in endurance athletes. Int J Sports Med 11(3):234-7, 1990.

In some cases of functional magnesium deficiency, such as in chronic fatigue states, there may be adequate levels of magnesium in the blood serum, but the magnesium fails to be adequately absorbed into the cells. In such cases vitamin B6 supplementation may assist in the transport of magnesium across the cell membrane. In one study, all members of a group of nine premenopausal women were found to have low red blood cell magnesium levels while only three had low plasma levels. After receiving 100 mg vitamin B6 twice a day their red cell magnesium levels rose significantly, and doubled after four weeks of therapy. (Abraham GE et al.: Effects of vitamin B6 on plasma and red blood cell magnesium levels in premenopausal women. Ann Clin Lab Sci 11(4):333-6, 1981.)

Comments

Oestrogen enhances the utilization of magnesium and its uptake by soft tissues and bone. This may explain why young women are resistant to heart disease and osteoporosis. However these effects of oestrogen may be harmful when oestrogen is high (as in the contraceptive pill and hormone replacement therapy) and magnesium levels are low. The resulting calcium/magnesium imbalance can favour blood clotting and thrombosis. (Seelig MS: Interrelationship of magnesium and estrogen in cardiovascular and bone disorders, eclampsia, migraine and premenstrual syndrome. J Am Coll Nutr 12(4):442-58, 1993.)

SUPPLEMENTATION

In research studies, magnesium supplements have been found to:

• Enhance strength gains during athletic training
• Improve chronic fatigue
• Improve circulation in peripheral vascular disease
• Improve fibromyalgia
• Improve glaucoma
• Improve glucose tolerance in late-onset diabetes
• Improve mitral valve prolapse
• Improve mood
• Improve osteoporosis
• Improve lung function in asthma patients
• Prevent angina attacks
• Prevent kidney stones
• Reduce abnormal heart rhythms
• Reduce noise-induced hearing loss
• Reduce high blood pressure
• Reduce myopathy associated with magnesium deficiency
• Reduce premenstrual symptoms and period pain
• Reduce reactive hypoglycaemia
• Reduce total cholesterol and raise HDL cholesterol
• Relieve migraine
• Reverse gum disease
• Treat eclampsia and pregnancy-induced high blood pressure

Preferred form and suggested intake

Good forms of magnesium supplements are magnesium citrate and magnesium taurate. Inorganic forms such as magnesium oxide or carbonate and dolomite are much less bioavailable. Combined calcium/magnesium supplements are often sold in a ratio containing twice as much calcium as magnesium. These products are probably not suitable for those trying to correct a magnesium deficiency.

Cautions

Since the body rejects excess magnesium, supplementation with this mineral is generally very safe, with the exception of individuals with kidney insufficiency.