Magnesium plays an important role in over 300 enzymatic reactions within the body including the metabolism of food, synthesis of fatty acids and proteins, and the transmission of nerve impulses.
Magnesium is one of the seven essential macrominerals; these are minerals that need to be consumed in relatively large amounts - at least 100 milligrams per day.
The human body contains approximately 25 grams of magnesium. Over 50 percent of that magnesium is stored in the skeletal system, and the rest is found in muscle, soft tissues, and bodily fluids.
Magnesium deficiency, especially prevalent in older populations, is linked to insulin resistance, metabolic syndrome, coronary heart disease, and osteoporosis.
This MNT Knowledge Center feature is part of a collection of articles on the health benefits of key vitamins and minerals. It provides an in-depth look at recommended intake of magnesium, its effects on health, foods high in magnesium, and any potential health risks of consuming too much magnesium.
Contents of this article:
Here are some key points about magnesium. More detail and supporting information is in the main article.
- Magnesium is vital for the proper functioning of hundreds of enzymes
- Consuming adequate magnesium might help reduce premenstrual symptoms
- For adult males, the recommended daily allowance of magnesium is 400-420 milligrams
- Sunflower seeds, almonds, and shrimp are some of the foods high in magnesium
Possible health benefits of magnesium
Magnesium supplements are available from stores, but it is best to obtain it through food.
The following health benefits have been associated with magnesium.
1) Bone health
Optimal magnesium intake is associated with greater bone density and improved bone crystal formation, as well as a lower risk of osteoporosis in postmenopausal women.
Magnesium plays an important role in carbohydrate and glucose metabolism, so it is no wonder magnesium status has an effect on diabetes.
Several studies have confirmed the inverse relationship between magnesium intake and the risk of diabetes. For every 100 milligrams per day increase in magnesium intake (up to a point), the risk of developing type 2 diabetes decreases by approximately 15 percent.
Most magnesium intake in these studies was from dietary sources, not supplements. Clinical studies have shown improvement in insulin sensitivity with a magnesium supplement intake of between 300 and 365 milligrams per day.
Researchers were also able to show that low magnesium levels resulted in impaired insulin secretion and lower insulin sensitivity.
3) Heart health
Magnesium is necessary to maintain the health of muscles, including the heart, and for the transmission of electrical signals in the body. Adequate magnesium intake has been associated with a lower risk of atherosclerosis (fatty buildup on the walls of arteries) and hypertension (high blood pressure).
More recently, several studies have found that a high intake of calcium without sufficient magnesium could increase the risk of arterial calcification and cardiovascular disease, as well as kidney stones.
In the Framingham Heart Study, people with the highest intake of magnesium were found to have a 58 percent lower chance of having coronary artery calcification and a 34 percent lower chance of abdominal artery calcification.
Rapid post-heart attack administration of magnesium reduces the risk of mortality, and magnesium is sometimes used as part of the treatment for congestive heart failure in order to lessen the risk of arrhythmia (abnormal heart rhythm).
Improvement in lipid profiles has been seen with an intake of 365 milligrams of magnesium per day.
4) Premenstrual syndrome
Research suggests that people experiencing premenstrual syndrome may be able to alleviate symptoms such as bloating, insomnia, leg swelling, weight gain, and breast tenderness by ensuring adequate intake of magnesium. Magnesium combined with vitamin B6 appears to be more effective.
5) Relieving anxiety
Reductions in magnesium, or alterations in the way that it is processed have been found to increase levels of anxiety. This appears to be through activity in the hypothalamic-pituitary-adrenal (HPA) axis - a set of three glands that controls our reaction to stress.
Research has shown that a low-magnesium diet alters the types of bacteria present in the gut and alters anxiety-based behavior.
Recommended magnesium intake
The Recommended Daily Allowance (RDA) for magnesium depends on age and gender. The National Institutes of Health recommend that children 1-3 years of age get 80 milligrams of magnesium a day, rising to 130 milligrams for children aged 4-8, and 240 milligrams for children aged 9-13.
After the age of 14, RDAs diverge for men and women, with men typically requiring more magnesium than women due to a larger average body mass. At the age of 14-18, the RDA for males is 410 milligrams, and 360 milligrams for females.
Adult females are advised to get 310-320 milligrams per day. An RDA of 350-400 milligrams is advised during pregnancy, and 310-360 milligrams when breastfeeding.
The RDA of magnesium for adult males is 400-420 milligrams.
The "bioavailability" of a nutrient refers to the degree to which it is absorbed and retained in the body for use. Magnesium has a medium level bioavailability; it is predominantly absorbed by the small intestine, with the efficiency of absorption depending on the amount of magnesium in the diet, the health of the gastrointestinal tract, the overall magnesium status of a person, and their diet as a whole. Unabsorbed magnesium is excreted in the feces.
Magnesium supplements are available, but it is best to obtain any vitamin or mineral through food as this increases the likelihood of ingesting optimal levels of other required and beneficial nutrients.
Many vitamins, minerals, and phytonutrients work synergistically, in other words, their benefits for health, when taken together, are greater than simply the sum of their individual benefits. As such, it is recommended to focus on meeting daily requirements for magnesium from foods before resorting to supplements as a backup.
Foods high in magnesium
Magnesium is found in a wide variety of foods, such as green leafy vegetables, nuts, seeds, brown rice, meat, and dairy.
The best sources of magnesium are nuts and seeds, dark green vegetables, whole grains, and legumes. Magnesium is also added to some breakfast cereals and other fortified foods.
- Sunflower seeds, dry roasted, 1/4 cup: 128 milligrams
- Almonds, dry-roasted, 1/4 cup: 105 milligrams
- Sesame seeds, roasted whole, 1 ounce: 101 milligrams
- Spinach, boiled, 1 cup: 78 milligrams
- Cashews, dry-roasted, 1 ounce: 74 milligrams
- Shredded wheat cereal, two large biscuits: 61 milligrams
- Soymilk, plain, 1 cup: 61 milligrams
- Black beans, cooked, 1/2 cup: 60 milligrams
- Oatmeal, cooked, 1 cup: 58 milligrams
- Broccoli, cooked, 1 cup: 51 milligrams
- Edamame, shelled, cooked, 1/2 cup: 50 milligrams
- Peanut butter, smooth, 2 tablespoons: 49 milligrams
- Shrimp, raw, 4 ounces: 48 milligrams
- Black-eyed peas, cooked, 1/2 cup: 46 milligrams
- Brown rice, cooked, 1/2 cup: 42 milligrams
- Kidney beans, canned, 1/2 cup: 35 milligrams
- Cow's milk, whole, 1 cup: 33 milligrams
- Banana, one medium: 33 milligrams
- Bread, whole-wheat, one slice: 23 milligrams
Magnesium is lost during the refinement process of wheat, so it is best to opt for cereals and bread products made with whole grains. Most common fruits, meat, and fish, are low in magnesium.
Possible health risks of consuming magnesium
Large doses of magnesium can cause a loss of central nervous system control. People with renal (kidney) insufficiency should not take magnesium supplements unless advised to do so by their physician.
No cases of magnesium toxicity from food intake have ever been reported, and such an occurrence seems highly unlikely to arise in any normal diet. However, if you are considering taking a supplement, there are certain drug interactions that people should be aware of.
Individuals taking any of the following medications should discuss magnesium supplements with their doctor before taking them:
- Mycophenolate Mofetil
- Mycophenolic Acid
It is the total diet or overall eating pattern that is most important in disease prevention and achieving good health. It is better to eat a diet with a variety than to concentrate on individual nutrients as the key to good health.