Magnesium

What is Magnesium and it’s functions?

Magnesium is an essential mineral for human nutrition and serves several important functions:

  • Contraction and relaxation of muscles
  • Function of certain enzymes in the body
  • Production and transport of energy
  • Production of protein

Food Sources

Most dietary magnesium comes from vegetables, such as dark green, leafy vegetables. Other foods that are good sources of magnesium:

  • Fruits or vegetables (such as bananas, dried apricots, and avocados)
  • Nuts (such as almonds and cashews)
  • Peas and beans (legumes), seeds
  • Soy products (such as soy flour and tofu)
  • Whole grains (such as brown rice and millet)

Approximately 30% to 40% of the dietary magnesium consumed is typically absorbed by the body.

Selected Food Sources of Magnesium
Food Milligrams
(mg) per
serving
Percent
DV*
Almonds, dry roasted, 1 ounce 80 20
Spinach, boiled, ½ cup 78 20
Cashews, dry roasted, 1 ounce 74 19
Peanuts, oil roasted, ¼ cup 63 16
Cereal, shredded wheat, 2 large biscuits 61 15
Soymilk, plain or vanilla, 1 cup 61 15
Black beans, cooked, ½ cup 60 15
Edamame, shelled, cooked, ½ cup 50 13
Peanut butter, smooth, 2 tablespoons 49 12
Bread, whole wheat, 2 slices 46 12
Avocado, cubed, 1 cup 44 15
Potato, baked with skin, 3.5 ounces 43 11
Rice, brown, cooked, ½ cup 42 11
Yogurt, plain, low fat, 8 ounces 42 11
Breakfast cereals, fortified with 10% of the DV for magnesium 40 10
Oatmeal, instant, 1 packet 36 9
Kidney beans, canned, ½ cup 35 9
Banana, 1 medium 32 8
Salmon, Atlantic, farmed, cooked, 3 ounces 26 7
Milk, 1 cup 24–27 6–7
Halibut, cooked, 3 ounces 24 6
Raisins, ½ cup 23 6
Chicken breast, roasted, 3 ounces 22 6
Beef, ground, 90% lean, pan broiled, 3 ounces 20 5
Broccoli, chopped and cooked, ½ cup 12 3
Rice, white, cooked, ½ cup 10 3
Apple, 1 medium 9 2
Carrot, raw, 1 medium 7 2

Side Effects of too Much Magnesium

Side effects from increased magnesium intake are not common because the body removes excess amounts. Magnesium excess almost always occurs only when magnesium is supplemented as a medication.

Lack of magnesium (deficiency) is rare. The symptoms include:

  • Hyperexcitability
  • Muscle weakness
  • Sleepiness

Deficiency of magnesium can occur in people who abuse alcohol or in those who absorb less magnesium due to:

  • Burns
  • Certain medications
  • Low blood levels of calcium
  • Problems absorbing nutrients from the intestinal tract (malabsorption)
  • Surgery

Symptoms due to a lack of magnesium have three categories.

Early symptoms:

  • Anorexia
  • Apathy
  • Confusion
  • Fatigue
  • Insomnia
  • Irritability
  • Muscle twitching
  • Poor memory
  • Reduced ability to learn

Moderate deficiency symptoms:

  • Heart (cardiovascular) changes
  • Rapid heartbeat

Severe deficiency:

  • Continued muscle contraction
  • Delirium
  • Numbness
  • Seeing or hearing things that aren’t there (hallucinations)
  • Tingling

Recommendations

These are the recommended daily requirements of magnesium:

  • Children
    • 1 – 3 years old: 80 milligrams
    • 4 – 8 years old: 130 milligrams
    • 9 – 13 years old: 240 milligrams
    • 14 – 18 years old (boys): 410 milligrams
    • 14 – 18 years old (girls): 360 milligrams
  • Adult females: 310 – 320 milligrams
  • Pregnancy: 350 – 400 milligrams
  • Breastfeeding women: 310 – 360 milligrams
  • Adult males: 400 – 420 milligrams

Magnesium and Health

Habitually low intakes of magnesium induce changes in biochemical pathways that can increase the risk of illness over time. This section focuses on four diseases and disorders in which magnesium might be involved: hypertension and cardiovascular disease, type 2 diabetes, osteoporosis, and migraine headaches.

Hypertension and cardiovascular disease

Hypertension is a major risk factor for heart disease and stroke. Studies to date, however, have found that magnesium supplementation lowers blood pressure, at best, to only a small extent. A meta-analysis of 12 clinical trials found that magnesium supplementation for 8–26 weeks in 545 hypertensive participants resulted in only a small reduction (2.2 mmHg) in diastolic blood pressure. The dose of magnesium ranged from approximately 243 to 973 mg/day. A diet containing more magnesium because of added fruits and vegetables, more low-fat or non-fat dairy products, and less fat overall has proven to lower systolic and diastolic blood pressure by an average of 5.5 and 3.0 mmHg, respectively.

Several prospective studies have examined associations between magnesium intakes and heart disease.  A systematic review and meta-analysis of prospective studies found that higher serum levels of magnesium were significantly associated with a lower risk of cardiovascular disease, and higher dietary magnesium intakes (up to approximately 250 mg/day) were associated with a significantly lower risk of ischemic heart disease caused by a reduced blood supply to the heart muscle.

Higher magnesium intakes might reduce the risk of stroke. In a meta-analysis of 7 prospective trials with a total of 241,378 participants, an additional 100 mg/day magnesium in the diet was associated with an 8% decreased risk of total stroke, especially ischemic rather than hemorrhagic stroke.

Type 2 diabetes

Diets with higher amounts of magnesium are associated with a significantly lower risk of diabetes, possibly because of the important role of magnesium in glucose metabolism. Hypomagnesemia might worsen insulin resistance, a condition that often precedes diabetes, or it might be a consequence of insulin resistance. Diabetes leads to increased urinary losses of magnesium, and the subsequent magnesium inadequacy might impair insulin secretion and action, thereby worsening diabetes control.

Most investigations of magnesium intake and risk of type 2 diabetes have been prospective cohort studies. In 2008, the American Diabetes Association stated in its nutrition recommendations for people with diabetes, “Health care providers should focus on nutrition counseling rather than micronutrient supplementation in order to reach metabolic control of their patients.

Osteoporosis

Magnesium is involved in bone formation and influences the activities of osteoblasts and osteoclasts. Magnesium also affects the concentrations of both parathyroid hormone and the active form of vitamin D, which are major regulators of bone homeostasis. Several population-based studies have found positive associations between magnesium intake and bone mineral density in both men and women. Other research has found that women with osteoporosis have lower serum magnesium levels than women with osteopenia and those who do not have osteoporosis or osteopenia. These and other findings indicate that magnesium deficiency might be a risk factor for osteoporosis.

Migraine headaches

Magnesium deficiency is related to factors that promote headaches, including neurotransmitter release and vasoconstriction. People who experience migraine headaches have lower levels of serum and tissue magnesium than those who do not.

However, research on the use of magnesium supplements to prevent or reduce symptoms of migraine headaches is limited.

In their evidence-based guideline update, the American Academy of Neurology and the American Headache Society concluded that magnesium therapy is “probably effective” for migraine prevention. Because the typical dose of magnesium used for migraine prevention exceeds the UL (upper limit), this treatment should be used only under the direction and supervision of a healthcare provider.

Resources

http://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/

http://www.nlm.nih.gov/medlineplus/ency/article/002423.htm