Every organ in the body, especially the heart, muscles, and kidneys, needs magnesium. This mineral also contributes to the makeup of teeth and bones. Magnesium activates enzymes, contributes to energy production, and helps regulate levels of calcium, copper, zinc, potassium, vitamin D, and other important nutrients in the body.
You can get magnesium from many foods. However, most people in the U.S. probably do not get as much magnesium as they should from their diet. Foods rich in magnesium include whole grains, nuts, and green vegetables. Green leafy vegetables are particularly good sources of magnesium.
Although you may not get enough magnesium from your diet, it is rare to be deficient in magnesium. However, certain medical conditions can upset the body's magnesium balance. For example, an intestinal virus that causes vomiting or diarrhea can cause a temporary magnesium deficiency. Some health conditions can lead to deficiencies, including:
- Gastrointestinal diseases, such as irritable bowel syndrome (IBS) and ulcerative colitis
- Hyperthyroidism (high thyroid hormone levels)
- Kidney disease
- Taking diuretics
Other factors that can lower magnesium levels include:
- Drinking too much coffee, soda, or alcohol
- Eating too much sodium (salt)
- Heavy menstrual periods
- Excessive sweating
- Prolonged stress
Symptoms of magnesium deficiency may include:
- Agitation and anxiety
- Restless leg syndrome (RLS)
- Sleep disorders
- Nausea and vomiting
- Abnormal heart rhythms
- Low blood pressure
- Muscle spasm and weakness
- Poor nail growth
Getting enough magnesium may enhance the effectiveness of conventional treatment for the following conditions:
Several studies show that intravenous (IV) magnesium and magnesium inhaled through a nebulizer can help treat acute attacks of asthma in adults and children, 6 to 18 years of age. But there is no evidence that taking oral magnesium helps control asthma symptoms. Low levels of magnesium may increase the risk of developing asthma. A population-based clinical study of more than 2,500 children, 11 to 19 years of age, found that low dietary magnesium intake may be associated with the risk of asthma. The same was found in a group of more than 2,600 adults, 18 to 70 years of age.
Inadequate magnesium appears to reduce serotonin levels, and antidepressants have been shown to raise brain magnesium. One study found that magnesium was as effective as tricyclic antidepressants in treating depression among people with diabetes.
People who have type 2 diabetes often have low blood levels of magnesium. A large clinical study of more than 2,000 people found that getting more magnesium in the diet may help protect against type 2 diabetes. Some studies suggest that taking magnesium supplements may help blood sugar control and insulin sensitivity in people with diabetes or prediabetes.
A preliminary clinical study of 24 people with fibromyalgia found that a proprietary tablet containing both malic acid and magnesium improved pain and tenderness associated with fibromyalgia when taken for at least 2 months. Other studies suggest the combination of calcium and magnesium may be helpful for some people with fibromyalgia. More studies are needed. Other studies suggest that magnesium supplementation helped improve muscle strength in children with cystic fibrosis.
Noise-related hearing loss
One study suggests that taking magnesium may prevent temporary or permanent hearing loss due to very loud noise.
Arrhythmia and heart failure
Magnesium is essential to heart health. Studies suggest a possible association between a modestly lower risk of coronary heart disease (CHD) in men and increased magnesium intake. In one study of women, higher dietary intake of magnesium was associated with a lower risk of sudden cardiac death. Magnesium helps maintain a normal heart rhythm and doctors sometimes administer it intravenously (IV) in the hospital to reduce the chance of atrial fibrillation and cardiac arrhythmia (irregular heartbeat). People with congestive heart failure (CHF) are often at risk for developing cardiac arrhythmia. For this reason, doctors may decide that magnesium should be a part of the treatment of CHF. One well-designed study found that taking magnesium orotate for a year reduced symptoms and improved survival rates in people with CHF when compared to placebo. Magnesium and calcium work together at very precise ratios to ensure your heart functions properly. Talk to your doctor before taking magnesium supplements if you have a history of cardiac issues.
Results of studies using magnesium to treat heart attack survivors have been mixed. Some studies reported lower death rates, as well as fewer arrhythmias and improved blood pressure when magnesium is used as part of the treatment following a heart attack. But one study found that magnesium slightly increased the risks of sudden death, the chance of another heart attack, or the need for bypass surgery in the year after a heart attack. If you have had a heart attack, your doctor will decide if magnesium supplementation is right for you.
High blood pressure (hypertension)
Eating low-fat dairy products and lots of fruits and vegetables on a regular basis is associated with lower blood pressure. All of these foods are rich in magnesium, as well as calcium and potassium. A large clinical study of more than 8,500 women found that a higher intake of dietary magnesium may reduce the risk of high blood pressure in women. A few studies also suggest that magnesium supplements may help lower blood pressure, although not all studies agree.
A few studies suggest that taking magnesium supplements may help prevent migraine headaches. In addition, research suggests that magnesium supplements may shorten the duration of a migraine and reduce the amount of medication needed. People who have migraine headaches tend to have lower levels of magnesium compared to those with tension headaches or no headaches at all.
Some experts recommend combining magnesium with vitamin B2 (riboflavin) and the herb feverfew when you have a headache.
However, some studies suggest that magnesium sulfate may be less effective than prescription medications for preventing migraines in those who have 3 or more headaches per month. The only exception to this may be women who get migraine headaches around the time of their period.
Not getting enough calcium, vitamin D, magnesium, and other micronutrients may play a role in the development of osteoporosis. To prevent osteoporosis, it is important to:
- Get enough calcium, magnesium, and vitamin D
- Eat a well-balanced diet
- Do weight bearing exercises throughout life
Preeclampsia and eclampsia
Preeclampsia is characterized by a sharp rise in blood pressure during the third trimester of pregnancy. Women with preeclampsia may develop seizures, which is then called eclampsia. Magnesium, given in the hospital by IV, is the treatment of choice to prevent or treat seizures associated with eclampsia or to prevent complications from preeclampsia. Some physicians also use magnesium sulfate to manage pre-term labor.
Premenstrual syndrome (PMS)
Scientific studies suggest that magnesium supplements may help relieve symptoms associated with PMS, particularly:
- Leg swelling
- Weight gain
- Breast tenderness
One study suggests that a combination of magnesium and vitamin B6 may work better than either one alone.
Restless legs syndrome (RLS)
A study including only 10 people found that magnesium improved insomnia related to RLS, a disorder characterized by uncomfortable sensations in the legs, which are worse during periods of inactivity, rest, or while sitting or lying down.
Preliminary studies suggest that higher intakes of dietary magnesium are associated with a lower risk of colorectal tumors. While this is a new area of research, scientists say consuming magnesium-rich foods may be another avenue to explore in the search for cancer prevention strategies.
Rich sources of magnesium include:
- Whole grains
- Green leafy vegetables
- Wheat bran
- Brazil nuts
- Soybean flour
- Blackstrap molasses
- Pumpkin and squash seeds
- Pine nuts
- Black walnuts
Other good dietary sources of this mineral include:
- Whole wheat flour
- Oat flour
- Beet greens
- Pistachio nuts
- Shredded wheat
- Bran cereals
- Baked potatoes (with skin)
- Cocoa powder
Also, many herbs, spices, and seaweeds supply magnesium, such as:
- Agar seaweed
- Dill weed
- Celery seed
- Dried mustard
- Fennel seed
- Cumin seed
- Poppy seed
Magnesium is available in many forms. Recommended forms include magnesium citrate, magnesium gluconate, and magnesium lactate, all of which are more easily absorbed into the body than other forms. Time release preparations may improve absorption. Ask your health care provider.
Other familiar sources are magnesium hydroxide (often used as a laxative or antacid) and magnesium sulfate (generally used orally as a laxative or in multivitamins, or added to a bath). Some magnesium, such as Epsom salts, can be absorbed through the skin. Preliminary research suggests Epsom salts can relieve swelling, inflammation, and ease muscle aches and pains.
How to Take It
Be sure to check with your health care provider before taking magnesium supplements and before giving them to a child. Under certain circumstances, such as certain heart arrhythmias or preeclampsia, a doctor will give magnesium by IV in the hospital.
It is a good idea to take a B-vitamin complex, or a multivitamin containing B vitamins, because the level of vitamin B6 in the body determines how much magnesium will be absorbed into the cells.
Dosages are based on the dietary reference intakes (DRIs) issued from the Food and Nutrition Board of the United States Government's Office of Dietary Supplements, part of the National Institutes of Health (NIH).
DO NOT give magnesium supplements to a child without a doctor's supervision.
- Children, 1 to 3 years of age: 80 mg daily
- Children, 4 to 8 years of age: 130 mg daily
- Children, 9 to 13 years of age: 240 mg daily
- Males, 14 to 18 years of age: 410 mg daily
- Females, 14 to 18 years of age: 360 mg daily
- Pregnant females, 14 to 18 years of age: 400 mg daily
- Breastfeeding females, 14 to 18 years of age: 360 mg daily
- Males, 19 to 30 years of age: 400 mg daily
- Females, 19 to 30 years of age: 310 mg daily
- Males, 31 years of age and over: 420 mg daily
- Females, 31 years of age and over: 320 mg daily
- Pregnant females, 19 to 30 years of age: 350 mg daily
- Pregnant females, 31 and over: 360 mg daily
- Breastfeeding females, 19 to 30 years of age: 310 mg daily
- Breastfeeding females, 31 years of age and over: 320 mg daily
A person's need for magnesium increases during pregnancy, recovery from surgery and illnesses, and athletic training. Speak with your doctor.
Because of the potential for side effects and interactions with medications, you should only take dietary supplements under the supervision of a knowledgeable health care provider.
Since magnesium is excreted by the kidneys, people with heart or kidney disease should not take magnesium supplements except under their doctors' supervision.
It is very rare to overdose on magnesium from food. However, people who ingest large amounts of milk of magnesia (as a laxative or antacid), Epsom salts (as a laxative or tonic), or magnesium supplements may overdose, especially if they have kidney problems. Too much magnesium can cause serious health problems, including:
- Severely lowered blood pressure
- Slowed heart rate
- Respiratory paralysis
- Deficiencies of other minerals
- Cardiac arrhythmias
- Cardiac arrest
More common side effects from magnesium include upset stomach and diarrhea.
Magnesium competes with calcium for absorption and can cause a calcium deficiency if calcium levels are already low. Some medications may lower magnesium levels in the body. These include:
- Chemotherapy drugs
- Digoxin (Lanoxin)
- Certain antibiotics
If you are currently being treated with any of the following medications, you should not use magnesium without talking to your health care provider first.
Aminoglycosides: Concomitant use with magnesium may cause neuromuscular weakness and paralysis.
Antibiotics: Taking magnesium supplements may reduce the absorption of quinolone antibiotics, tetracycline antibiotics, and nitrofurantoin (Macrodandin). Magnesium should be taken 1 hour before or 2 hours after taking these medications. Quinolone and tetracycline antibiotics include:
- Ciprofloxacin (Cipro)
- Moxifloxacin (Avelox)
- Tetracycline (Sumycin)
- Doxycycline (Vibramycin)
- Minocycline (Minocin)
Blood pressure medications, calcium channel blockers: Magnesium may increase the risk of negative side effects (such as dizziness, nausea, and fluid retention) from calcium channel blockers (particularly nifedipine or Procardia) in pregnant women. Other calcium channel blockers include:
- Aamlodipine (Norvasc)
- Diltiazem (Cardizem)
- Felodipine (Plendil)
- Verapamil (Calan)
Medications for diabetes: Magnesium hydroxide, commonly found in antacids such as Alternagel, may increase the absorption of some medications used to control blood sugar levels (particularly glipizide or Glucatrol and glyburide or Micronase). If you take these medications to control blood sugar, your doctor may need to adjust your dose.
Digoxin (Lanoxin): Low blood levels of magnesium can increase negative effects from digoxin, including heart palpitations and nausea. In addition, digoxin can cause more magnesium to be lost in the urine. A doctor will monitor magnesium levels in people taking digoxin to see whether they need a magnesium supplement.
Diuretics: Loop diuretics (such as furosemide and bumetanide) and thiazide (including hydrochlorothiazide) can lower magnesium levels. For this reason, doctors who prescribe diuretics may recommend magnesium supplements as well.
Fluoroquinones: Concomitant use with magnesium may decrease absorption and effectiveness. Fluoroquinones should be taken at least 4 hours before any products containing magnesium.
Hormone replacement therapy (HRT): Magnesium levels tend to decrease during menopause. Clinical studies suggest, however, that HRT may help prevent the loss of this mineral. Postmenopausal women, or those taking HRT, should talk with their doctors about the risks and benefits of magnesium supplementation.
Labetol: Concomitant use with magnesium can abnormally slow your heart beat and reduce cardiac output.
Levomethadyl: Concomitant use with magnesium may precipitate a heart condition called QT prolongation.
Levothyroxine: There have been case reports of magnesium-containing antacids reducing the effectiveness of levothyroxine, a medication that treats underactive thyroid.
Penicillamine: Penicillamine, a medication used to treat rheumatoid arthritis (RA) and Wilson's disease (a condition characterized by high levels of copper in the body), can deactivate magnesium, particularly when high doses of the medicine are used over a long period of time. Supplementation with magnesium and other nutrients may reduce side effects associated with penicillamine. If you take penicillamine, your doctor should determine whether magnesium supplements are right for you.
Tiludronate (Skelid) and alendronate (Fosamax): Magnesium may interfere with absorption of medications used for osteoporosis, including alendronate (Fosamax). Magnesium or antacids containing magnesium should be taken 1 hour before or 2 hours after taking these medications.
Others: Aminoglycoside antibiotics (such as gentamicin and tobramycin), amphotericin B, corticosteroids (prednisone or Deltasone), antacids, and insulin may lower magnesium levels.
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