Magnesium Overview

Magnesium is an essential nutrient, meaning that your body needs it for healthy functioning. It is found in significant quantities throughout the body and used for numerous purposes, including muscle relaxation, blood clotting, and the manufacture of ATP (adenosine triphosphate, the body's main energy molecule).

It has been called nature's calcium channel blocker. The idea refers to magnesium's ability to block calcium from entering muscle and heart cells. A group of prescription heart medications work in a similar way, although much more powerfully. This may be the basis for some of magnesium's effects when it is taken as a supplement in fairly high doses.

Requirements for magnesium increase as we grow and age. The official US and Canadian recommendations for daily intake are as follows:

• Infants

• 0-6 months: 30 mg

• 7-12 months: 75 mg

• Children

• 1-3 years: 80 mg

• 4-8 years: 130 mg

• Males

• 9-13 years: 240 mg

• 14-18 years: 410 mg

• 19-30 years: 400 mg

• 31 years and older: 420 mg

• Females

• 9-13 years: 240 mg

• 14-18 years: 360 mg

• 19-30 years: 310 mg

• 31 years and older: 320 mg

• Pregnant Women

• 18 years and younger: 400 mg

• 19-30 years: 350 mg

• 31-50 years: 360 mg

• Nursing Women

• 18 years and younger: 360 mg

• 19-30 years: 310 mg

• 31-50 years: 320 mg

Note: These recommendations refer to total intake from food plus supplements. The average diet provides a daily intake of magnesium very close to these amounts.

In the United States, the average dietary intake of magnesium is lower than the recommended daily allowance; however, it is unclear whether this truly indicates deficiency, or if the recommended allowance is too high. ¹ Alcohol abuse , surgery , diabetes , zinc supplements, certain types of diuretics ( thiazide and loop diuretics , but not potassium-sparing diuretics ), estrogen and oral contraceptives , and the medications cisplatin and cyclosporin have been reported to reduce the body's level of magnesium or increase magnesium requirements. ² If you are taking potassium supplements, you may receive greater benefit from them if you take extra magnesium as well.

While it is sometimes said that calcium interferes with magnesium absorption, this effect is apparently too small to have a significant effect on overall magnesium status. ³

Kelp is very high in magnesium, as are wheat bran, wheat germ, almonds, and cashews. Other good sources include blackstrap molasses, brewer's yeast (not to be confused with nutritional yeast), buckwheat, nuts, and whole grains. You can also get appreciable amounts of magnesium from collard greens, dandelion greens, avocado, sweet corn, cheddar cheese, sunflower seeds, shrimp, dried fruit (figs, apricots, and prunes), and many other common fruits and vegetables.

A typical supplemental dosage of magnesium ranges from the nutritional needs described above to as high as 600 mg daily. For premenstrual syndrome (PMS) and dysmenorrhea (painful menstruation), an alternative approach is to start taking 500 to 1,000 mg daily, beginning on day 15 of the menstrual cycle and continuing until menstruation begins.

Magnesium citrate may be slightly more absorbable than other forms of magnesium. ⁴

Migraine Headaches

A double-blind study found that regular use of magnesium helps prevent migraine headaches . In this 12-week trial, 81 people with recurrent migraines were given either 600 mg of magnesium daily or placebo. ⁵ By the last 3 weeks of the study, the treated group's migraines had been reduced by 41.6%, compared to a reduction of 15.8% in the placebo group. The only side effects observed were diarrhea (in about one-fifth of the participants) and, less often, digestive irritation.

Similar results have been seen in other smaller double-blind studies. ⁶ One study found no benefit, ⁷ but it has been criticized on many significant points, including using an excessively strict definition of what constituted benefit. ⁸

Noise-related Hearing Loss

One double-blind, placebo-controlled study on 300 military recruits suggests that 167 mg of magnesium daily can prevent hearing loss due to exposure to high-volume noise. ⁹

Kidney Stones

Magnesium inhibits the growth of calcium oxalate stones in the test tube ¹⁰ and decreases stone formation in rats. ¹¹ However, human studies have had mixed results. In one 2-year open study, 56 people taking magnesium hydroxide had fewer recurrences of kidney stones than 34 people not given magnesium. ¹² In contrast, a double-blind (and, hence, more reliable) study of 124 people found that magnesium hydroxide was essentially no more effective than placebo. ¹³

Hypertension

Magnesium works with calcium and potassium to regulate blood pressure . Several studies suggest that magnesium supplements can reduce blood pressure in people with hypertension, ^{14 15 16} although some have not.

Angina

In a double-blind, placebo-controlled trial of 187 people with angina , 6 months of treatment with magnesium at a dose of 730 mg daily improved exercise tolerance and enhanced overall quality of life. ¹⁷ Benefits were also seen in a similar, smaller double-blind trial. ¹⁸

After a Heart Attack

In a 1-year, double-blind, placebo-controlled trial of 468 individuals who had just experienced a heart attack , use of a magnesium supplement at a dose of 360 mg daily failed to prevent heart-related events (defined as heart attack, sudden cardiac death, or need for cardiac bypass), and actually may have increased the risk slightly. ¹⁹

Dysmenorrhea

A 6-month, double-blind, placebo-controlled study of 50 women with menstrual pain found that treatment with magnesium significantly improved symptoms. ²⁰ The researchers reported evidence of reduced levels of prostaglandin F 2 alpha, a hormone-like substance involved in pain and inflammation.

Similarly positive results were seen in a double-blind, placebo-controlled study of 21 women. ²¹

Premenstrual Syndrome Symptoms

A double-blind, placebo-controlled study of 32 women found that magnesium taken from day 15 of the menstrual cycle to the onset of menstrual flow could significantly improve PMS symptoms, specifically mood changes. ²² Another small double-blind preliminary study found that regular use of magnesium could reduce symptoms of PMS-related fluid retention. ²³ In this study, 38 women were given magnesium or placebo for 2 months. The results showed no effect after one cycle, but by the end of two cycles, magnesium significantly reduced weight gain, swelling of extremities, breast tenderness, and abdominal bloating.

In addition, one small double-blind study (20 participants) found that magnesium supplementation can help prevent menstrual migraines. ²⁴ Preliminary evidence suggests that the combination of magnesium and vitamin B 6 might be more effective than either treatment alone. ²⁵

Pregnancy-induced Leg Cramps

Pregnant women frequently experience painful leg cramping. One double-blind trial of 73 pregnant women found that 3 weeks of magnesium supplements significantly reduced leg cramps as compared to placebo. ²⁶

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