I found your articles on Restless Legs Syndrome
and Nocturnal Leg Cramps (BPJ
49, Dec 2012) disappointing, because no clear causes were outlined and the treatment options were poor.
For the following reasons I believe the working hypothesis to use in our medical practice, as to the primary cause
of both conditions, should be magnesium deficiency:
- No other simple explanation has been proposed
- Magnesium is an essential factor for the healthy function of nerves and muscles
- Widespread soil mineral deficiencies and mineral losses in food preparation combine to make the magnesium intake
inadequate for many people. The requirement for magnesium is large, with the human body needing about half the mass
of its sodium requirement.
- The statement that: “Magnesium supplementation has no benefit in the treatment of nocturnal cramps” is an inaccurate
summation of the conclusions of the research quoted in the Cochrane review. Of the four studies referenced, only two
were of published studies relating to oral supplementation. These studies by Frusso et al 1999 and Roffe et al 2002,
both noted a significant period effect i.e. improvement in cramp occurrence with time as magnesium treatment continued.
However all six oral studies quoted, including those in pregnancy, were flawed because they used too low a dose of magnesium
and/or poorly absorbed magnesium, for too short a time. Any serious attempt to treat the symptoms of magnesium deficiency
with oral supplementation to raise the total body magnesium content requires months of magnesium amino acid chelate
(glycinate) or perhaps magnesium of marine origin, in a dose of at least 500 mg elemental magnesium per day if tolerated.
- Anecdotal accounts of benefit of magnesium supplementation for both conditions are widespread
In a review of my practice database covering the last 11 years and eight months, 99 current adult patients with a Read
code diagnosis of cramp (N2472.00) were found. Of these, 92 had received advice on the use of magnesium supplementation,
and in subsequent consultations cramp had settled in 88. In four there was a reduced amount of cramp, and of the four
patients who reported ongoing cramp, two were found to have been taking no magnesium. All eight patients over the last
three months have received further advice to take a higher dose of a better absorbed magnesium preparation, and will
be reviewed again in due course.
In the last year only two patients have been prescribed quinine. One was a short supply for a patient with severe cramp
occurring in multiple sites, to use over the time needed for a magnesium supplement to take effect. The other and only
patient requiring an ongoing supply has chosen to take the advice of a specialist who initiated the prescribing of quinine.
Diuretics increase renal loss of magnesium, and appear to increase the tendency to cramp and restless legs syndrome.
Therefore in this practice in order for benefit from magnesium supplementation to not be sabotaged by diuretic action,
the use of frusemide, bumetanide and thiazides is minimised and where possible replaced by spironolactone.
I have made the following observations in clinical practice and have assumed they are common knowledge, but they were
also omitted from the restless legs article:
- The sleep deprivation restless legs causes becomes in itself a major cause of the restless legs syndrome; i.e. it
becomes self-perpetuating, with the increased fatigue from the inability to get to sleep increasing the restless legs
condition the next night
- The most effective acute management of restless legs is cooling, and in particular running cold water over the legs
in the bath or shower
- Much safer and cheaper medicines than those suggested in the article are effective in controlling restless legs,
such as ¼ to 1 tablet of dihydrocodeine (DHC) 60 mg, each evening. Later, after magnesium supplementation takes effect,
if needed restless legs may be controlled with paracetamol 500 mg plus codeine 8 mg tablets, or clonidine 25 – 50 mcg
Observations made in my clinical practice over decades have contributed to the above hypotheses and conclusions, and
there should be research to confirm them. However there is a great deal of health knowledge which has been gained in
general practice by doctors listening carefully to what patients tell us, and this huge source of information and learning
should not be ignored.
Dr Ralph Brock-Smith, General Practitioner
Editorial comment: There are few robust studies on the use of magnesium for nocturnal cramps or restless
legs syndrome. Studies include only a small number of participants and have shown limited evidence of effectiveness.
Reviews of the balance of evidence have concluded that magnesium is unable to be recommended as an effective treatment
for nocturnal cramps or restless legs syndrome. The data reported by the correspondent undoubtedly demonstrates an association
between patients taking magnesium and experiencing an improvement in their symptoms of cramp/restless legs. However,
what this data does not definitively reveal is causality. The patients’ symptoms may have remitted spontaneously over
time, or because of other non-pharmacological interventions the patients may have undertaken. The debate, therefore,
centres on whether giving magnesium to patients with nocturnal cramps or restless legs may cause harm. Magnesium is
considered safe at doses no greater than the upper recommended level of intake for supplements of 350 mg/day for adults.*
Adverse effects associated with excessive use of magnesium, i.e. hypermagnesaemia, include diarrhoea, nausea, vomiting
and thirst, and in more serious cases, hypotension, arrhythmias and respiratory depression. Perhaps of greater concern
are the limitations on the use of diuretic medicines in these patients. In addition, although some of the medicines
recommended for unremitting restless legs syndrome and nocturnal cramps are associated with adverse effects, dihydrocodeine
and clonidine are not without potentially significant adverse effects also.
* Australian Government Department of Health and Ageing, National Health and Medical Research Council.
Nutrient reference values for Australia and New Zealand. 2006. Available from: