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.
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.
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
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.
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 (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.
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