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.⁷ 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.⁸ Many doctors suggest magnesium supplements of 300 mg per day.

Magnesium deficiency has been proposed as one cause of the symptoms that occur in association with MVP.⁹ 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.¹⁰

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.¹¹ Lower serum concentrations of magnesium were found to be associated with a higher incidence of arrhythmia in a large population study.¹² 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,¹³ but it does not appear to prevent atrial fibrillation.¹⁴ A doctor should supervise any use of magnesium for cardiac arrhythmia.

Magnesium deficiency may be a contributing factor for spasms that occur in coronary arteries, particularly in variant angina.^15,16 While studies have used injected magnesium to stop such attacks effectively,^17,18 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.¹⁹

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.²⁴ Protection from stroke associated with drinking water high in magnesium has also been reported.²⁵ Intravenous magnesium given immediately after a stroke has been proposed as a treatment for reducing stroke deaths,²⁶ but results so far have been inconclusive.²⁷

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.²⁸ 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.²⁹

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.³⁰ One group of researchers reported that 47% of people with COPD had a magnesium deficiency.³¹ 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.³² 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.³³ The effect of oral magnesium supplementation in people with COPD has yet to be investigated.

Abnormalities of magnesium metabolism have been reported in people with Raynaud’s disease.³⁴ Symptoms similar to those seen with Raynaud’s disease occur in people with magnesium deficiency,³⁵ probably because a deficiency of this mineral results in spasm of blood vessels.³⁶ 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.

Magnesium plays a role in controlling muscle tone and could be important in preventing menstrual cramps.^37,38 Magnesium supplements have been reported in preliminary and double-blind European research to reduce symptoms of dysmenorrhea.^39,40,41 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.⁴⁰

Women with PMS have been reported to be at increased risk of magnesium deficiency.^42,43 Supplementing with magnesium may help reduce symptoms.^44,45 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).⁴⁶ Magnesium has also been reported to be effective in reducing the symptoms of menstrual migraine headaches.⁴⁷ While the ideal amount of magnesium has yet to be determined, some doctors recommend 400 mg per day.⁴⁸ Effects of magnesium may begin to appear after two to three months.

Numerous studies have shown that poor magnesium status is associated with insulin resistance and type 2 diabetes.^53,54,55,56 Furthermore, diabetes itself causes increased magnesium loss, resulting in a vicious cycle of dropping magnesium levels and worsening insulin resistance.^57,58 Low magnesium levels have also been correlated with poor blood glucose control and increased risk of complications such as heart disease, kidney disease, and nerve damage in those with type 2 diabetes.^{59,60,61,62,63} Moreover, meta-analyses of randomized controlled trials have concluded that magnesium supplementation can lower blood pressure and decrease the risk of diabetes-related cardiovascular disease in people with type 2 diabetes.^64,65

Taking 250 mg of elemental magnesium (from magnesium oxide, gluconate, and lactate) per day for three months improved glycemic control and insulin sensitivity in a randomized controlled trial with 42 participants with type 2 diabetes.⁶⁶ In a placebo-controlled trial, patients with diabetes-related kidney failure taking 250 mg of elemental magnesium (from magnesium oxide) per day for 24 weeks had improved vascular health, as well as reduced insulin, total cholesterol, LDL-cholesterol, and C-reactive protein levels, Hgb1c values, and insulin resistance scores, and increased antioxidant capacity.⁶⁷ However, another placebo-controlled trial that included people with type 2 diabetes and related kidney disease found the combination of 250 mg magnesium (from magnesium oxide) plus 47 mg calcium (from calcium carbonate) per day improved lipid profiles but had no effect on glucose control and worsened insulin resistance after 12 weeks.⁶⁸ Many doctors recommend that people with diabetes supplement with 200 to 600 mg per day of elemental magnesium from a highly bioavailable magnesium salt without added calcium.

Research has shown that supplementing with chromium (200 mcg per day)⁷³ or magnesium (340 mg per day)⁷⁴ 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.⁷⁵ Other nutrients, including vitamin C, vitamin E, zinc, copper, manganese, and vitamin B6, may help control blood sugar levels in diabetics.⁷⁶ 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.

Low blood levels of magnesium have been found to be a risk factor for retinopathy in white people with diabetes,^77,78 but not in black people with diabetes.⁷⁹ So far, no studies have determined whether supplementing with magnesium would help prevent the development of retinopathy.

Magnesium plays a role in controlling muscle tone and could be important in preventing menstrual cramps.^80,81 Magnesium supplements have been reported in preliminary and double-blind European research to reduce symptoms of dysmenorrhea.^82,83,84 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.⁸³

Women with PMS have been reported to be at increased risk of magnesium deficiency.^85,86 Supplementing with magnesium may help reduce symptoms.^87,88 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).⁸⁹ Magnesium has also been reported to be effective in reducing the symptoms of menstrual migraine headaches.⁹⁰ While the ideal amount of magnesium has yet to be determined, some doctors recommend 400 mg per day.⁹¹ Effects of magnesium may begin to appear after two to three months.

Compared with healthy people, people with migraines have been found to have lower blood and brain levels of magnesium.^92,93,94,95 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.⁹⁶ 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.⁹⁷ Another double-blind trial found that taking 360 mg of magnesium per day decreased the number of days on which premenstrual migraines occurred.⁹⁸ 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.⁹⁹ Intravenous magnesium has been reported to produce marked and sometimes complete symptom relief during acute migraines, usually within 15 minutes or less.¹⁰⁰

People who suffer from cluster headaches often have low blood levels of magnesium, and preliminary trials^104,105 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.

Magnesium deficiency has also been implicated as a possible cause of GH.^106,107,108 Dietary intake of magnesium is below recommended levels for many women during pregnancy.^109,106 Magnesium supplementation has been reported to reduce the incidence of GH in preliminary¹⁰⁶ and many double-blind trials.^112,113,114 In addition to preventing GH, magnesium supplementation has also been reported to reduce the severity of established GH in one study.¹¹⁵ Amounts used in studies on GH range from 165 to 365 mg of supplemental magnesium per day.

Magnesium deficiency has been implicated as a possible cause of preeclampsia.^{116,117,118,119,120} Magnesium supplementation has been shown to reduce the incidence of preeclampsia in high-risk women in one trial,¹²¹ but not in another double-blind trial.¹¹⁷

In a preliminary study, people with osteoporosis were reported to be at high risk for magnesium malabsorption.¹²⁴ Both bone¹²⁵ and blood¹²⁶ levels of magnesium have been reported to be low in people with osteoporosis. Supplemental magnesium has reduced markers of bone loss in men.¹²⁷ 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.¹²⁸ 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.¹²⁹ 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.¹³⁰ 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.

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.¹³¹ Compared with 25 other magnesium-deficient ADHD children, those given magnesium supplementation had a significant decrease in hyperactive behavior.

Some researchers have added magnesium to vitamin B6, reporting that taking both nutrients may have better effects than taking B6 alone.¹³² 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).¹³³

Magnesium levels are frequently low in asthmatics.¹³⁴ 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,^{135,136,137,138} but not all,¹³⁹ 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.¹⁴⁰ 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.¹⁴¹ 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.¹⁴²

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.¹⁴³Zinc malabsorption also occurs frequently in celiac disease¹⁴⁴ and may result in zinc deficiency, even in people who are otherwise in remission.¹⁴⁵ 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.¹⁴⁶

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.¹⁴⁷ 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.¹⁴⁸ 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.¹⁴⁹ 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.^150,151,152 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.

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.¹⁵³

Low blood levels of magnesium have been found to be a risk factor for retinopathy in white people with diabetes,^154,155 but not in black people with diabetes.¹⁵⁶ So far, no studies have determined whether supplementing with magnesium would help prevent the development of retinopathy.

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).¹⁵⁷

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).¹⁵⁸

Many years ago, magnesium was reported to be relaxing for people with mild anxiety.¹⁷¹ 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.

Many years ago, magnesium was reported to be relaxing for people with mild anxiety.¹⁷² 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.