The human body contains around 25g of magnesium, whereof approximately 50 to 60% are in bones1. Magnesium is required in more than 300 enzyme processes1. A deficiency leads to a weakening of the body and diseases. An excess intake is not a problem.
Magnesium is important in many functions in the human body. The first recognizable symptom of a deficiency is often over-excitability of muscles and especially cramps.1.
Other symptoms are: loss of appetite, nausea, vomiting, fatigue and weakness2. As the deficiency progresses possible are: numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal hears rhythms, as well as coronary spasms2.
Longer term too low magnesium intake seems to be related to: heart attack, high blood pressure, bone fragility (osteoporosis), diabetes mellitus1.
As a consequence of magnesium deficiency often also calcium deficiency develops. The blood serum concentration of calcium can drop significantly even before any symptoms of magnesium deficiency become identifiable1.
It is not possible to eat too much magnesium with normal food1. The body excretes too much magnesium with urine1. As long as there are no intestine or kidney diseases, magnesium from food is absolutely harmless1.
The consequence of an overdose of supplements is usually diarrhea with sometimes nausea and stomach cramps1.
Life threatening much magnesium in the body usually only occurs with infusions or kidney problems1. It may be possible with oral supplements, but large quantities would have to be eaten and it almost never occurs.
Recommended Daily Intake (Total)
The recommended daily allowance from all sources (normal food, supplements etc. together) is according to the Institute of Medicine (US) as follows:
|Male 19-30 years||400mg per day1|
|Female 19-30 years||310mg per day|
|Male 31 and older||420mg per day1|
|Female 31 and older||320mg per day|
|Pregnant||from 360mg to 400mg per day|
|Lactating||from 320mg to 360mg per day|
The detailed tables by age and gender can be found here.
Assessment of Status
There are tests to inspect a possible magnesium deficiency.
Magnesium Blood Serum Test
It is the most common test. A result below 0.75 mmol/liter (1.8 mg/dl) shows a magnesium deficiency1. When having insufficient magnesium intake, the body can use up magnesium stored in bones, muscles and internal organs and stabilize the magnesium blood level in a normal range, although a deficiency exists3. That means it is possibly to have magnesium deficiency and still have blood serum levels in the normal range.
There is a multitude of other tests, which can theoretically be administered. Magnesium is stored to 90% in the muscles and bones1 and only 0.3% circulates in the blood serum4. Different kinds of cells in the body can be tested directly for their magnesium content, e.g. mouth mucosa, lymphocytes, muscle cells, red blood cells etc. Another test consists of consuming magnesium and then measuring in the following 24 hours how much is being excreted again with urine5. The less magnesium the body excretes again, the higher is his need for magnesium and therefore the stronger the deficiency.
There are different tests available. A single, simple, cheap, available and accurate test for the personal magnesium status does not exist, yet. Each test has his weaknesses in one or another aspect. The most common blood serum test is inaccurate.
In the table below some examples of the magnesium content of food is listed.
|Lettuce, green 11||13mg|
|Dark chocolate, 60-69% cacao14||176mg|
|Milk18 (ca. 1 dl)||10mg|
|Cheese, Gruyere 19||36mg|
|Cheese, Brie 20||20mg|
In a normal diet around 50% of the magnesium in the food is absorbed1.
Phytic acid occurs in many food types, like for example the outer shell of many grains (whole grains)21. Phytic acid reduces the magnesium absorption21. For grains sprouting before processing helps to reduce the amount of phytic acid22. Spinach contains much oxalic acid23. Oxalic acid also interferes with usage of magnesium by the body23,21.
Types of Supplements
There are different magnesium compounds sold as supplements.
- Magnesium citrate
- Magnesium oxide
- Magnesium chloride
- Magnesium lactate
- Magnesium aspartate
- ... others
For magnesium in normal food there are no adverse effects known1.
The Institute of Medicine (US) has published a maximal dosage for supplements. It is based on the intake from where upward diarrhea starts to occur.
The value is 350mg (8 years and older) 1.
More detailed tables by age and gender are available here.
Magnesium supplements are available in every grocery or drug store.
A light magnesium deficiency is often not recognized, because the symptoms are only weak and many other deficiencies or diseases have similar symptoms (e.g. fatigue). The first recognizable symptom are usually cramps.
A deficiency can be cured with supplements.
An overdose is not a health risk as long as there are no kidney diseases.