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Magnesium Supplements Not Helpful for Nighttime Leg Cramps

Worst Pills, Best Pills Newsletter article July, 2017

Nocturnal or nighttime leg cramps (charley horses) are very common in adults, afflicting nearly half of those over the age of 50.[1] While not serious, they can cause sudden, incapacitating pain and disrupt sleep.

For many years, magnesium supplements have been marketed around the world for prevention of leg cramps despite a lack of evidence that they provide benefit.[2],[3] The largest and most rigorous clinical trial to evaluate magnesium for preventing leg cramps was published by JAMA...

Nocturnal or nighttime leg cramps (charley horses) are very common in adults, afflicting nearly half of those over the age of 50.[1] While not serious, they can cause sudden, incapacitating pain and disrupt sleep.

For many years, magnesium supplements have been marketed around the world for prevention of leg cramps despite a lack of evidence that they provide benefit.[2],[3] The largest and most rigorous clinical trial to evaluate magnesium for preventing leg cramps was published by JAMA Internal Medicine in May 2017. The trial revealed that magnesium was no better than a placebo for controlling this often distressing condition.

Facts About Leg Cramps

Leg cramps are caused by sudden, involuntary contractions of one or more muscles.[4] They occur most commonly in the calf muscles and sometimes in the muscles of the feet or thighs. They usually occur while in bed — when either awake or sleeping — but some patients also experience them during the daytime.[5]

During a calf cramp, a hard knot usually can be felt, and the feet and toes typically are pulled into a downward pointing position. The cramps may last a few seconds to several minutes and will spontaneously resolve without treatment. The affected muscle may be sore for several hours after the cramp has ended.

Approximately 40 percent of people with nocturnal leg cramps experience them at least three nights per week, and 5 to 10 percent have them nightly.[6]

For most affected people, leg cramps are not due to any underlying medical condition, and the precise reason for their occurrence is unknown.[7]

Leg cramps frequently occur in pregnant women and tend to worsen as pregnancy progresses.[8] Medical conditions that can cause leg cramps include:[9],[10]

  • dehydration and depletion of sodium chloride (salt) and other minerals;
  • structural disorders of the feet, such as flat feet;
  • neurologic diseases, including diabetic nerve damage and Parkinson’s disease; and
  • hormone disorders, such as low or high thyroid hormone levels.

Multiple drugs also are associated with the occurrence of leg cramps. The evidence for such an association is strongest for inhaled long-acting beta agonists (for example, salmeterol [ADVAIR, SEREVENT]) and certain diuretics (water pills, such as hydrochlorothiazide [MICROZIDE]), which can lead to dehydration and salt depletion.[11]

Prior research

In 2012, researchers published a systematic review that analyzed data from four randomized clinical trials that compared magnesium with a placebo for the prevention of muscle cramps in non-pregnant adults.[12] The trials were small, enrolling between 40 and 73 subjects. For the largest trial, 27 subjects dropped out before it was completed, so data were available for only 46 subjects. For all four trials, the average age of the subjects was older than 60.

Three of the trials each tested different oral forms of magnesium — magnesium citrate tablets, magnesium lactate tablets and magnesium citrate powder dissolved in water — given daily. The fourth trial tested a course of magnesium sulfate administered intravenously (injected into a vein) over four hours on five consecutive days, a regimen that would not be very practical for someone experiencing leg cramps.

The analysis of data from these four trials revealed that the magnesium treatments did not significantly reduce the number, intensity or duration of leg cramps. The authors of the 2012 systematic review concluded that it was unlikely that magnesium supplements provide meaningful benefit in the prevention of muscle cramps in older adults.

The new trial

For the new JAMA Internal Medicine trial, researchers in Israel tested a different form of magnesium called magnesium oxide.[13] They selected this form because recent research had shown that consuming oral magnesium oxide resulted in greater increases in magnesium levels within the cells of healthy volunteers than did magnesium citrate.

In 2013, the researchers recruited 94 adults who were living independently at home and had experienced at least four nighttime leg cramps during an initial two-week screening period. The researchers randomly assigned the subjects, who had an average age of 65, to receive either magnesium oxide capsules or placebo capsules before bedtime for four weeks. To minimize the potential for bias, neither the researchers nor the subjects knew which subjects were taking magnesium and which were taking placebo capsules.

Each morning during the trial — including the initial two-week screening phase and the four-week treatment period — subjects recorded the number, severity and duration of any leg cramps experienced during the previous night. They also completed surveys that measured overall quality of life and quality of sleep at the time of initial enrollment and within one week of completing the four-week treatment period.

The researchers found no significant differences in the number, severity or duration of nighttime leg cramps between the magnesium and placebo groups. Interestingly, subjects in both groups experienced approximately three fewer nighttime cramps per week than they did in the baseline screening period. These decreases, which were statistically significant, indicate that there was a significant placebo effect. Finally, there were no differences in measures of overall quality of life or quality of sleep between the two groups.

Like the authors of the 2012 systematic review, the researchers conducting the new trial concluded that it appears unlikely that older adults with nighttime cramps will benefit significantly from magnesium supplements.

What You Can Do

We recommend that you not use magnesium supplements to prevent leg cramps because there is no evidence that they are effective. You also should never use quinine (QUALAQUIN) — which used to be prescribed commonly for this condition — because it can cause life-threatening adverse reactions, including blood clotting disorders, sudden kidney failure and abnormal heart rhythms.[14]

If you experience a leg cramp, you should forcefully stretch the affected muscle.[15] For example, if you develop a cramp in the calf muscle, try to flex your foot so that the toes point upward toward your head. Other measures to help stretch a cramped calf muscle include pushing your foot flat against the headboard or a bedpost or standing up with your foot flat on the floor and pressing down firmly. Massaging the muscle and applying heat or ice also may help.

To prevent cramps, you should avoid dehydration and, if possible, drugs that are associated with muscle cramps. You also should try daily stretching exercises for the leg muscles: Lean forward against a wall or other support while keeping your legs straight and your feet flat on the floor. Hold this position for 10 to 20 seconds and repeat three to five times. Initially do this several times per day and before bedtime.[16] One randomized clinical trial showed that nightly stretching before bedtime reduced the frequency and severity of nocturnal leg cramps.[17] Other preventive measures that may help include briefly riding a stationary bike before bedtime and keeping bed covers at the foot of the bed loose and untucked.[18]

References

[1] Winkelman JW. Nocturnal leg cramps. Updated October 17, 2016. UpToDate. https://www.uptodate.com/contents/nocturnal-leg-cramps. Accessed May 2, 2017.

[2] Maor NR, Alperin M, Shturman E, et al. Effect of magnesium oxide supplementation on nocturnal leg cramps: A randomized clinical trial. JAMA Intern Med. 2017;177(5):617-623.

[3] Magnesium Diasporal. Magnesium for cramp in the calf and muscle tension. 2015. http://www.diasporal.com/magnesium-for-muscle-cramp-in-the-calfs-and-muscle-tensions/. Accessed May 2, 2017.

[4] Monderer RS, Wu WP, Thorpy MJ. Nocturnal leg cramps. Curr Neurol Neurosci Rep. 2010;10(1):53-59.

[5] Winkelman JW. Nocturnal leg cramps. Updated October 17, 2016. UpToDate. https://www.uptodate.com/contents/nocturnal-leg-cramps. Accessed May 2, 2017.

[6] Ibid.

[7] Allen RE, Kirby KA. Nocturnal leg cramps. Am FamPhysician. 2012;86(4):350-355.

[8] Monderer RS, Wu WP, Thorpy MJ. Nocturnal leg cramps. Curr Neurol Neurosci Rep. 2010;10(1):53-59.

[9] Ibid.

[10] Winkelman JW. Nocturnal leg cramps. Updated October 17, 2016. UpToDate. https://www.uptodate.com/contents/nocturnal-leg-cramps. Accessed May 2, 2017.

[11] Ibid.

[12] Garrison SR, Allan GM, Sekhon RK, et al. Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews 2012, Issue 9. Art. No.: CD009402. DOI: 10.1002/14651858.CD009402.pub2.

[13] Maor NR, Alperin M, Shturman E, et al. Effect of magnesium oxide supplementation on nocturnal leg cramps: A randomized clinical trial. JAMA Intern Med. 2017;177(5):617-623.

[14] Food and Drug Administration. Serious risks associated with using Quinine to prevent or treat nocturnal leg cramps (September 2012). August 31, 2012. https://www.fda.gov/forhealthprofessionals/learningactivities/ucm317811.htm. Accessed May 2, 2017.

[15] Winkelman JW. Nocturnal leg cramps. Updated October 17, 2016. UpToDate. https://www.uptodate.com/contents/nocturnal-leg-cramps. Accessed May 2, 2017.

[16] Ibid.

[17] Hallegraeff JM, van der Schans CP, de Ruiter R, de Greef MH. Stretching before sleep reduces the frequency and severity of nocturnal leg cramps in older adults: a randomised trial. J Physiother. 2012;58(1):17-22.

[18] Winkelman JW. Nocturnal leg cramps. Updated October 17, 2016. UpToDate. https://www.uptodate.com/contents/nocturnal-leg-cramps. Accessed May 2, 2017.

Disclaimer

The information on this website is not intended to substitute for professional medical advice, diagnosis, or treatment. Consult your doctor before changing or discontinuing any medication.