Magnesium

DESCRIPTION

Quantitatively, magnesium ranks next to Phosphorus and Calcium in the body. Magnesium is intimately involved with Calcium in metabolism.

Magnesium is widely distributed in the soft tissues and in the skeleton, which contains up to 70% of the total body content. If dietary intake falls, the body protects against magnesium loss by a reduction in urinary excretion, allowing conservation of the mineral for future use. Magnesium must be present in adequate amount for Calcium to be assimilated. As magnesium tends to be poorly absorbed from the diet, deficiency can be widespread.

FUNCTIONS

More than 65% of the magnesium content of the body is found in the bone, where along with Calcium and phosphorus it provides structure and strength.

The mineral plays a pivotal role in energy release, as it is a cofactor in energy-releasing reactions. It is also needed in RNA synthesis and in DNA replication - i.e. in cell production. Additionally, magnesium is important in the functioning of nerves and muscles (including the heart muscle). It is sometimes referred to as the ‘anti-Stress’ mineral, because of its role in muscle relaxation. It is also required for the repair and maintenance of body cells and tissues as a co-factor in protein metabolism.

DEFICIENCY

According to Dr. Mildred Seelig, a leading authority on magnesium, deficiency of this mineral is very wide spread in Western countries. Deficiency may be caused by:

Reduced dietary intake as in poor diet, malnutrition, anorexia nervosa, or high raw bran intake.
Reduced or impaired absorption caused by malabsorption conditions such as: chronic Diarrhoea, gastro-intestinal Infections or allergies.
The symptoms of magnesium deficiency are likely to be:

Muscle Cramps and twitches
Low blood sugar
Anxiety
Insomnia

REQUIREMENTS

Upper safe level for daily supplementation = 350mg

Recommended Daily Allowance = 300mg

SUPPLEMENTAL USES

The following are known to deplete magnesium levels:

Long term use of diuretics (1)
Diarrhoea
Alcohol (1)
Excessive sweating

PMS:
Magnesium is also often taken by women to ease Pre-menstrual syndrome, especially stomach cramps and sugar cravings. The use of magnesium in this situation makes a lot of sense because tests have borne out that blood magnesium levels decrease in women with PMS (2).

Muscle Function:
Other conditions that people sometimes find magnesium helps with are involuntary muscle twitches (e.g. of the eyelid) and combined with calcium> for muscle cramps. Again in relation to muscle function, it is also thought that magnesium has some protective effect on the heart (1), perhaps more particularly by lowering blood pressure and LDL cholesterol levels (3).

Asthma:
Magnesium has been shown to reduce wheezing (4) and may be an important factor in Asthma and chronic-obstructive airways disease.

SAFETY

As with calcium, there is no evidence to suggest that large intakes of magnesium are harmful to humans with normal kidney function. Excessive circulating levels of magnesium are almost impossible to achieve by ingestion from foods, but high levels induced by intravenous administration can interfere with nerve transmission and are therefore very dangerous. 3-5g of magnesium salts has a purgative action and is harmful if taken frequently for this purpose.

INTERACTIONS AND CONTRA-INDICATIONS

Calcium and B6:
Magnesium requires the presence of Calcium for its proper absorption and utilisation. Vitamin B6 and Phosphorus are also helpful in this regard.

Antibiotics:
Magnesium can interfere with the function of tetracycline antibiotics and so these two should be taken a few hours apart.

FOOD SOURCES

Food (mg/100g)
Peanuts, roasted 180
Bread, wholemeal 76
Cheese, cheddar 25
Fish, white 23
Chicken 21
Beef, stewing steak 18
Potatoes 17
Oranges 13
Eggs 12
Milk 10

REFERENCES

1. "Handbook of Dietary Supplements", Pamela Mason, Blackwell Science, 1995.
2. Rosenstein DL et al. Magnesium measures across the menstrual cycle in premenstrual syndrome. Biol Psychiatry, 35;8:557-571, 1994.
3. Itoh K et al. The effects of high oral magnesium supplementation on blood pressure serum lipids and related variables in apparently healthy Japanese subjects. The British J of Nutrition, 78;5:737-750, 1997.
4. Britton J et al. Dietary magnesium, lung function, wheezing, and airway hyperreactivity in a random adult population sample. The Lancet, 344:357-362, 1994.