A double-blind trial investigated the effect of oral magnesium supplementation on arrhythmic episodes in people with congestive heart failure. Those people taking 3.2 grams per day of magnesium chloride (equivalent to 384 mg per day of elemental magnesium) had between 23% and 52% fewer occurrences of specific types of arrhythmia during the six-week study, compared with those taking placebo.¹ Lower serum concentrations of magnesium were found to be associated with a higher incidence of arrhythmia in a large population study.² The anti-arrhythmic properties of magnesium appear to be specific. For example, magnesium is clearly able to prevent a drug-induced arrhythmia called torsade de pointes,³ but it does not appear to prevent atrial fibrillation.⁴ A doctor should supervise any use of magnesium for cardiac arrhythmia.

Magnesium deficiency frequently occurs in people with CHF, and such a deficiency may lead to heart arrhythmias. Magnesium supplements have reduced the risk of these arrhythmias.⁵ People with CHF are often given drugs that deplete both magnesium and potassium; a deficiency of either of these minerals may lead to an arrhythmia.⁶ Many doctors suggest magnesium supplements of 300 mg per day.

Magnesium plays a role in controlling muscle tone and could be important in preventing menstrual cramps.^{7, 8} Magnesium supplements have been reported in preliminary and double-blind European research to reduce symptoms of dysmenorrhea.^{9, 10, 11} In one of these double-blind trials, women took 360 mg per day of magnesium for three days beginning on the day before menses began.¹²

Magnesium deficiency has also been implicated as a possible cause of GH.^{13, 14, 15} Dietary intake of magnesium is below recommended levels for many women during pregnancy.^{16, 17} Magnesium supplementation has been reported to reduce the incidence of GH in preliminary¹⁸ and many double-blind trials.^{19, 20} In addition to preventing GH, magnesium supplementation has also been reported to reduce the severity of established GH in one study.²¹ Amounts used in studies on GH range from 165 to 365 mg of supplemental magnesium per day.

Compared with healthy people, people with migraines have been found to have lower blood and brain levels of magnesium.^{22 , 23 , 24 , 25} Preliminary research in a group of women (mostly premenopausal) showed that supplementing with magnesium (usually 200 mg per day) reduced the frequency of migraines in 80% of those treated.²⁶ In a double-blind trial of 81 people with migraines, 600 mg of magnesium per day was significantly more effective than placebo at reducing the frequency of migraines.²⁷ Another double-blind trial found that taking 360 mg of magnesium per day decreased the number of days on which premenstrual migraines occurred.²⁸ One double-blind trial found no benefit from 486 mg of magnesium per day for three months. However, that study defined improvement according to extremely strict criteria, and even some known anti-migraine drugs have failed to show benefit when tested using those criteria.²⁹ Intravenous magnesium has been reported to produce marked and sometimes complete symptom relief during acute migraines, usually within 15 minutes or less.³⁰

Magnesium deficiency has been proposed as one cause of the symptoms that occur in association with MVP.³¹ In a study of people with severe MVP symptoms, blood levels of magnesium were low in 60% of cases. Those people with low magnesium levels participated in a double-blind trial, in which they received a placebo or magnesium (500 mg per day for one week, then about 335 mg per day for four weeks). People receiving magnesium experienced a significant reduction in symptoms of weakness, chest pain, anxiety, shortness of breath, and palpitations.³²

People with type 2 diabetes tend to have low magnesium levels.³⁸ Double-blind research indicates that supplementing with magnesium overcomes this problem.³⁹ Magnesium supplementation has improved insulin production in elderly people with type 2 diabetes.⁴⁰ However, one double-blind trial found no effect from 500 mg magnesium per day in people with type 2 diabetes, although twice that amount led to some improvement.⁴¹ Elders without diabetes can also produce more insulin as a result of magnesium supplements, according to some,⁴² but not all, trials.⁴³ However, in people with type 2 diabetes who nonetheless require insulin, Dutch researchers have reported no improvement in blood sugar levels from magnesium supplementation.⁴⁴ The American Diabetes Association acknowledges strong associations between magnesium deficiency and insulin resistance but has not said magnesium deficiency is a risk factor⁴⁵ Many doctors, however, recommend that people with diabetes and normal kidney function supplement with 200 to 600 mg of magnesium per day.

Diabetes-induced damage to the eyes is more likely to occur in magnesium-deficient people with type 1 diabetes.⁴⁶ In magnesium-deficient pregnant women with type 1 diabetes, the lack of magnesium may even account for the high rate of spontaneous abortion and birth defects associated with type 1 diabetes.⁴⁷ The American Diabetes Association admits “strong associations...between magnesium deficiency and insulin resistance” but will not say magnesium deficiency is a risk factor.⁴⁸ Many doctors, however, recommend that people with diabetes and normal kidney function supplement with 200–600 mg of magnesium per day.

Magnesium deficiency may be a contributing factor for spasms that occur in coronary arteries, particularly in variant angina.^{51, 52} While studies have used injected magnesium to stop such attacks effectively,^{53, 54} it is unclear whether oral magnesium would be effective in preventing or treating blood vessel spasms. One double-blind study of patients with exercise-induced angina, however, showed that oral magnesium supplementation (365 mg twice a day) for 6 months significantly reduced the incidence of exercise-induced chest pain, compared with a placebo.⁵⁵

Magnesium levels are frequently low in asthmatics.⁵⁶ Current evidence suggests that high dietary magnesium intake may be associated with better lung function and reduced bronchial reactivity. Intravenous injection of magnesium has been reported in most,^{57, 58, 59, 60} but not all,⁶¹ double-blind trials to rapidly halt acute asthma attacks. Magnesium supplements might help prevent asthma attacks because magnesium can prevent spasms of the bronchial passages. In a preliminary trial, 18 adults with asthma took 300 mg of magnesium per day for 30 days and experienced decreased bronchial reactivity.⁶² However, a double-blind trial investigated the effects of 400 mg per day for three weeks and found a significant improvement in symptoms, but not in objective measures of airflow or airway reactivity.⁶³ The amount of magnesium used in these trials was 300 to 400 mg per day. Children usually take proportionately less based on their body weight, but one study of asthmatic children between the ages of 17 and 19 used 300 mg of magnesium per day.⁶⁴

Some children with ADHD have lowered levels of magnesium. In a preliminary, controlled trial, children with ADHD and low magnesium status were given 200 mg of magnesium per day for six months.⁶⁵ Compared with 25 other magnesium-deficient ADHD children, those given magnesium supplementation had a significant decrease in hyperactive behavior.

The malabsorption that occurs in celiac disease can lead to multiple nutritional deficiencies. The most common nutritional problems in people with celiac disease include deficiencies of essential fatty acids, iron, vitamin D, vitamin K, calcium, magnesium, and folic acid.⁶⁶ Zinc malabsorption also occurs frequently in celiac disease⁶⁷ and may result in zinc deficiency, even in people who are otherwise in remission.⁶⁸ People with newly diagnosed celiac disease should be assessed for nutritional deficiencies by a doctor. Celiac patients who have not yet completely recovered should supplement with a high-potency multivitamin-mineral. Some patients may require even higher amounts of some of these vitamins and minerals—an issue that should be discussed with their healthcare practitioner. Evidence of a nutrient deficiency in a celiac patient is a clear indication for supplementation with that nutrient.

After commencement of a gluten-free diet, overall nutritional status gradually improves. However, deficiencies of some nutrients may persist, even in people who are strictly avoiding gluten. For example, magnesium deficiency was found in 8 of 23 adults with celiac disease who had been following a gluten-free diet and were symptom-free. When these adults were supplemented with magnesium for two years, their bone mineral density increased significantly.⁶⁹

NADH (nicotinamide adenine dinucleotide) helps make ATP, the energy source the body runs on. In a double-blind trial, people with CFS received 10 mg of NADH or a placebo each day for four weeks.⁷⁰ Of those receiving NADH, 31% reported improvements in fatigue, decreases in other symptoms, and improved overall quality of life, compared with only 8% of those in the placebo group. Further double-blind research is needed to confirm these findings.

Magnesium levels have been reported to be low in CFS sufferers. In a double-blind trial, injections with magnesium improved symptoms for most people.⁷¹ Oral magnesium supplementation has improved symptoms in those people with CFS who previously had low magnesium levels, according to a preliminary report, although magnesium injections were sometimes necessary.⁷² These researchers report that magnesium deficiency appears to be very common in people with CFS. Nonetheless, several other researchers report no evidence of magnesium deficiency in people with CFS.^{73, 74, 75} The reason for this discrepancy remains unclear. If people with CFS do consider magnesium supplementation, they should have their magnesium status checked by a doctor before undertaking supplementation. It appears that only people with magnesium deficiency benefit from this therapy.

In a preliminary study, people with osteoporosis were reported to be at high risk for magnesium malabsorption.⁷⁶ Both bone⁷⁷ and blood⁷⁸ levels of magnesium have been reported to be low in people with osteoporosis. Supplemental magnesium has reduced markers of bone loss in men.⁷⁹ Supplementing with 250 mg up to 750 mg per day of magnesium arrested bone loss or increased bone mass in 87% of people with osteoporosis in a two-year, preliminary trial.⁸⁰ Supplementing with magnesium (150 mg per day for one year) also increased bone mass in pre-adolescent and adolescent girls in a double-blind study.⁸¹ Some doctors recommend that people with osteoporosis supplement with 350 mg of magnesium per day.

One trial studying postmenopausal women combined hormone replacement therapy with magnesium (600 mg per day), calcium (500 mg per day), vitamin C, B vitamins, vitamin D, zinc, copper, manganese, boron, and other nutrients for an eight- to nine-month period.⁸² In addition, participants were told to avoid processed foods, limit protein intake, emphasize vegetable over animal protein, and limit consumption of salt, sugar, alcohol, coffee, tea, chocolate, and tobacco. Bone density increased a remarkable 11%, compared to only 0.7% in women receiving hormone replacement alone.

Women with PMS have been reported to be at increased risk of magnesium deficiency.^{83 , 84} Supplementing with magnesium may help reduce symptoms.^{85 , 86} In one double-blind trial using only 200 mg per day for two months, a significant reduction was reported for several symptoms related to PMS (fluid retention, weight gain, swelling of extremities, breast tenderness, and abdominal bloating).⁸⁷ Magnesium has also been reported to be effective in reducing the symptoms of menstrual migraine headaches.⁸⁸ While the ideal amount of magnesium has yet to be determined, some doctors recommend 400 mg per day.⁸⁹ Effects of magnesium may begin to appear after two to three months.

Test tube studies have shown that propionyl-L-carnitine (a form of L-carnitine) protects red blood cells of people with thalassemia against free radical damage.⁹⁰ In a preliminary study, children with beta thalassemia major who took 100 mg of L-carnitine per 2.2 pounds of body weight per day for three months had a significantly decreased need for blood transfusions.⁹¹ Some studies have found people with thalassemia to be frequently deficient in folic acid, vitamin B12,⁹² and zinc.^{93 , 94} Researchers have reported improved growth rates in zinc-deficient thalassemic children who were given zinc supplements of 22.5 to 90 mg per day, depending on age.^{95 , 96} Magnesium has been reported to be low in thalassemia patients in some,^{97 , 98} but not all,⁹⁹ studies. A small, preliminary study reported that oral supplements of magnesium, 7.2 mg per 2.2 pounds of body weight per day, improved some red blood cell abnormalities in thalassemia patients.¹⁰⁰

Alcoholics are sometimes deficient in magnesium, and some researchers believe that symptoms of withdrawal may result in part from this deficiency.¹⁰¹ Nonetheless, a double-blind trial reported that magnesium injections did not reduce symptoms of alcohol withdrawal.¹⁰²

Many years ago, magnesium was reported to be relaxing for people with mild anxiety.¹⁰³ Typically, 200 to 300 mg of magnesium are taken two to three times per day. Some doctors recommend soaking in a hot tub containing 1–2 cups of magnesium sulfate crystals (Epsom salts) for 15 to 20 minutes, though support for this approach remains anecdotal.

Some researchers have added magnesium to vitamin B6, reporting that taking both nutrients may have better effects than taking B6 alone.¹¹⁶ The amount of magnesium—10 to 15 mg per 2.2 pounds of body weight—is high enough to cause diarrhea in some people and should be administered by a doctor. Doctors will often try vitamin B6 or the combination of B6 and magnesium for at least three months to see whether these nutrients help autistic children. In a preliminary trial, one group of researchers found that relatively small daily amounts of magnesium (6 mg per 2.2 pounds of body weight) and vitamin B6 (0.6 mg per 2.2 pounds of body weight) improved symptoms by about 50% in children with autism or a related condition (pervasive developmental disorder).¹¹⁷

Many prescription drugs commonly taken by people with COPD have been linked to magnesium deficiency, a potential problem because magnesium is needed for normal lung function.¹¹⁸ One group of researchers reported that 47% of people with COPD had a magnesium deficiency.¹¹⁹ In this study, magnesium deficiency was also linked to increased hospital stays. Thus, it appears that many people with COPD may be magnesium deficient, a problem that might worsen their condition; moreover, the deficiency is not easily diagnosed.

Intravenous magnesium has improved breathing capacity in people experiencing an acute exacerbation of COPD.¹²⁰ In this double-blind study, the need for hospitalization also was reduced in the magnesium group (28% versus 42% with placebo), but this difference was not statistically significant. Intravenous magnesium is known to be a powerful bronchodilator.¹²¹ The effect of oral magnesium supplementation in people with COPD has yet to be investigated.

People who suffer from cluster headaches often have low blood levels of magnesium, and preliminary trials^{122 , 123} show that intravenous magnesium injections may relieve a cluster headache episode. However, no trials have investigated the effects of oral magnesium supplementation on cluster headaches.

A preliminary trial found that a combination of magnesium and malic acid might lessen muscle pain in people with fibromyalgia.¹²⁴ The amounts used in this trial were 300–600 mg of elemental magnesium and 1,200–2,400 mg of malic acid per day, taken for eight weeks. A double-blind trial by the same research group using 300 mg magnesium and 1,200 mg malic acid per day found no reduction in symptoms, however.¹²⁵ Though these researchers claimed that magnesium and malic acid appeared to have some effect at higher levels (up to 600 mg magnesium and 2,400 mg malic acid), the positive effects were not demonstrated under blinded study conditions. Therefore, the evidence supporting the use of these supplements for people with fibromyalgia remains weak and inconclusive.

Magnesium can dilate blood vessels. One study looked at whether magnesium might improve vision in people with glaucoma by enhancing blood flow to the eyes. In that trial, participants were given 245 mg of magnesium per day. Improvement in vision was noted after four weeks, but the change did not reach statistical significance.¹²⁶

Research has shown that supplementing with chromium (200 mcg per day)¹³¹ or magnesium (340 mg per day)¹³² can prevent blood sugar levels from falling excessively in people with hypoglycemia. Niacinamide (vitamin B3) has also been found to be helpful for hypoglycemic people.¹³³ Other nutrients, including vitamin C, vitamin E, zinc, copper, manganese, and vitamin B6, may help control blood sugar levels in diabetics.¹³⁴ Since there are similarities in the way the body regulates high and low blood sugar levels, these nutrients might be helpful for hypoglycemia as well, although the amounts needed for that purpose are not known.

Some people have difficulty sleeping because of a problem known as period limb movements during sleep (PLMS) or another condition called restless legs syndrome (RLS). In a preliminary trial, people with PLMS or RLS who suffered from insomnia had a significant improvement in sleep efficiency after supplementing with magnesium (about 300 mg each evening for four to six weeks).¹³⁵

Magnesium deficiency can reduce insulin sensitivity,¹³⁶ and low dietary intake¹³⁷ and low blood levels¹³⁸ of magnesium have been associated with greater insulin resistance in nondiabetic people. However, no studies of magnesium supplementation in people with IRS have been done.

Magnesium may increase blood flow by helping to dilate blood vessels. A preliminary trial found that magnesium supplementation may increase walking distance in people with intermittent claudication.¹³⁹ Many doctors suggest that people with atherosclerosis, including those with intermittent claudication, take approximately 250 to 400 mg of magnesium per day.

In a preliminary trial, supplementing with evening primrose oil (approximately 1,600 mg per day) led to a 10% increase in exercise tolerance in people with intermittent claudication.¹⁴⁰

In a small preliminary trial, people with MS were given 20 grams of cod liver oil, as well as approximately 680 mg of magnesium and 1,100 mg of calcium per day in the form of dolomite tablets.¹⁴¹ After one year, the average number of MS attacks decreased significantly for each person. Unlike fish oil capsules, the cod liver oil in this trial contained not only eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), but 5,000 IU of vitamin D. Therefore, it is not known whether the vitamin D or fatty acids were responsible for the cod liver oil’s effects. (One preliminary study found that giving vitamin D-like drugs to animals with MS was helpful.)¹⁴² It is also possible that the magnesium and/or calcium given to these people reduced MS attacks. Magnesium¹⁴³ and calcium¹⁴⁴ levels have been reported to be lower in the nerve tissue of people with MS compared with healthy people.

Magnesium deficiency has been implicated as a possible cause of preeclampsia.^{145, 146, 147, 148, 149} Magnesium supplementation has been shown to reduce the incidence of preeclampsia in high-risk women in one trial,¹⁵⁰ but not in another double-blind trial.¹⁵¹

Abnormalities of magnesium metabolism have been reported in people with Raynaud’s disease.¹⁵² Symptoms similar to those seen with Raynaud’s disease occur in people with magnesium deficiency,¹⁵³ probably because a deficiency of this mineral results in spasm of blood vessels.¹⁵⁴ Some doctors recommend that people with Raynaud’s disease supplement with 200–600 mg of magnesium per day, although no clinical trials support this treatment.

In a preliminary trial, people with period limb movements during sleep (PLMS) or RLS who suffered from insomnia had a significant improvement in sleep efficiency after supplementing with magnesium (about 300 mg each evening for four to six weeks).¹⁵⁵

Low blood levels of magnesium have been found to be a risk factor for retinopathy in white people with diabetes,^{156 , 157} but not in black people with diabetes.¹⁵⁸ So far, no studies have determined whether supplementing with magnesium would help prevent the development of retinopathy.

Low concentrations of red blood cell magnesium have been noted in patients with sickle cell anemia.^{159 , 160} Low magnesium, in turn, is thought to contribute to red blood cell dehydration and a concomitant increase in symptoms. In a preliminary trial, administration of 540 mg of magnesium per day for six months to sickle cell anemia patients reversed some of the characteristic red blood cell abnormalities and dramatically reduced the number of painful days for these patients.¹⁶¹ The form of magnesium used in this trial, magnesium pidolate, is not supplied by most magnesium supplements; it is unknown whether other forms of magnesium would produce similar results.

Researchers have found an association between diets low in magnesium and increased risk of stroke, an effect explained partially, but not completely, by the ability of magnesium to reduce high blood pressure.¹⁶² Protection from stroke associated with drinking water high in magnesium has also been reported.¹⁶³ Intravenous magnesium given immediately after a stroke has been proposed as a treatment for reducing stroke deaths,¹⁶⁴ but results so far have been inconclusive.¹⁶⁵