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MAGNESIUM:
Physiology
and Clinical Effects
Magnesium is needed for bone, protein, and fatty acid formation, making
new cells, activating B vitamins, relaxing muscles, clotting blood, and
forming ATP—the energy the body runs on. Insulin secretion and function
also require magnesium.
Magnesium also
acts in a way related to calcium channel blocker drugs. This effect may be
responsible for the fact that under certain circumstances, magnesium has
been found to potentially improve vision in people with glaucoma in
preliminary research.1 Similarly, this action might account for
magnesium’s ability to lower blood pressure.2
Because
magnesium has so many different actions in the body, the exact reasons for
some of its clinical effects are difficult to determine. For example,
magnesium has reduced hyperactivity in children in preliminary research.3
Other research suggests that some children with ADD have lowered levels of
magnesium. In a preliminary but controlled trial, 50 ADD children with low
magnesium (as determined by red blood cell, hair, and serum levels of
magnesium) were given 200 mg of magnesium per day for six months.4
Compared with 25 other magnesium-deficient ADD children, those given
magnesium supplementation had a significant decrease in hyperactive
behavior.
Magnesium
levels have been reported to be low in those with chronic fatigue syndrome
(CFS), while magnesium injections have been reported to improve symptoms.5
Oral magnesium supplementation has also improved symptoms in those people
with CFS who had low magnesium levels in another report, although
magnesium injections were sometimes necessary.6 However, other
research reports no evidence of magnesium deficiency in people with CFS.7
8 The reason for this discrepancy remains unclear. People with
CFS considering magnesium supplementation should have their magnesium
status checked beforehand by a doctor. Only people with magnesium
deficiency appear to benefit from this therapy.
Food
Sources
Nuts and grains are good sources of magnesium. Beans, dark green
vegetables, fish, and meat also contain significant amounts.
Deficiency
Risk and Symptoms
Magnesium deficiency is common in people taking “potassium-depleting”
prescription drugs. Taking too many laxatives can also lead to deficiency.
Alcoholism, severe burns, diabetes, and heart failure are other potential
causes of deficiency.
Almost
two-thirds of people in intensive care hospital units have been found to
be magnesium deficient.9 Deficiency is also associated with
chronic diarrhea, pancreatitis, and other conditions associated with
malabsorption.
Fatigue,
abnormal heart rhythms, muscle weakness and spasm, depression, loss of
appetite, listlessness, and potassium depletion can all result from a
magnesium deficiency.
Deficiencies
of magnesium that are serious enough to cause symptoms should be treated
by medical doctors, as they might require IV administration of magnesium.10
Recommended
Dosage
Most people don’t consume enough magnesium. Many doctors recommend
250–350 mg per day for adults.
Contraindications
Taking too much magnesium often leads to diarrhea. For some people this
can happen with amounts as low as 350–500 mg per day. More serious
problems can develop with excessive magnesium intake from
magnesium-containing laxatives; however, the amounts of magnesium found in
nutritional supplements are unlikely to cause such problems. People with
kidney disease should not take magnesium supplements without consulting a
doctor.
Vitamin B6
increases the amount of magnesium that can enter cells. As a result, these
two nutrients are often taken together. Magnesium may compete for
absorption with other minerals, particularly calcium. Taking a
multimineral supplement avoids this potential problem.
References:
1. Gaspar AZ,
Gasser P, Flammer J. The influence of magnesium on visual field and
peripheral vasospasm in glaucoma. Ophthalmologica
1995;209:11–3.
2. Kawano Y, Matsuoka H, Takishita S, Omae T. Effects of magnesium
supplementation in hypertensive patients. Hypertension
1998;32:260–5.
3. Starobrat-Hermelin B, Kozielec T. The effects of magnesium
physiological supplementation on hyperactivity in children with attention
deficit hyperactivity disorder (ADHD): Positive response to magnesium oral
loading test. Magnesium Res 1997;10:149–56.
4. Starobrat-Hermelin B, Kozielec T. The effects of magnesium
physiological supplementation on hyperactivity in children with attention
deficit hyperactivity disorder (ADHD). Positive response to magnesium oral
loading test. Magnes Res 1997;10:149–56.
5. Cox IM, Campbell MJ, Dowson D. Red blood cell magnesium and chronic
fatigue syndrome. Lancet 1991;337:757–60.
6. Howard JM, Davies S, Hunnisett A. Magnesium and chronic fatigue
syndrome. Lancet 1992;340:426.
7. Gantz NM. Magnesium and chronic fatigue. Lancet 1991;338:66
[letter].
8. Hinds G, Bell NP, McMaster D, McCluskey DR. Normal red cell magnesium
concentrations and magnesium loading tests in patients with chronic
fatigue syndrome. Ann Clin Biochem 1994;31(Pt 5):459–61.
9. Weisinger JR, Bellorin-font, E. Magnesium and phosphorus. Lancet
1998;352:391–6 [review].
10. Weisinger JR, Bellorin-font, E. Magnesium and phosphorus. Lancet
1998;352:391–6 [review].
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