Magnesium in foodstuffs and beverages
Magnesium is the eighth most common element of the earth and is found in its natural state as a mineral in the form of carbonates, silicates, chlorides and sulphates. Magnesium is commonly found both in fauna and flora.
Physiological function
In the human body, the most important intracellular cations are magnesium and potassium. Depending on a person's body weight and constitution, a human body contains 20 - 28g of magnesium. About 60% of it is found in the form of hydroxylapatite in the bones and teeth. Another 35% is intracellularly localised, especially in soft tissue such as muscles. The remaining 5% is found in extracellular fluids.
As an essential co-factor, magnesium is involved in more than 300 enzymatic reactions. Magnesium plays an important role in muscular metabolism. In addition, magnesium is a physiological calcium antagonist and impedes calcium-dependent excitation states in the body, which is of much significance for
neuromuscular stimuli transfer.
This mineral substance also has cardioprotective properties, for example by expanding coronary and peripheral blood vessels, reducing thrombocyte aggregation and lowering blood lipid levels.
Magnesium and nutrition
Magnesium is found in foodstuffs of vegetable and animal origin. In plant tissues it mainly occurs as a central atom of the chlorophyll, which means that all green vegetables are important sources of magnesium. Mineral and spa waters (> 100 mg/l), which are rich in magnesium, can make a major contribution to the body's magnesium supply when consuming 1 - 1.5 litres per day. Drinking water, on the other hand, usually only contains low levels of this mineral.
Metabolism
The absorption of magnesium takes place all along the small intestine, with an average absorption rate of approximately 30 to 40%. The exact transport mechanisms have not been finally established, but it is thought that low concentrations of magnesium are absorbed by an active mechanism, while higher concentrations are passively absorbed by diffusion.
The availability of magnesium in food is reduced by various dietetic factors. These include, for example, a diet containing high levels of free fatty acids, fibre, zinc, oxalate or phytate. Alcohol, too, impedes intestinal resorption.
Contrary to long-held opinions, long-term magnesium balance studies have found that a diet rich in calcium does not inhibit magnesium absorption.
Recommendations for magnesium supply
The exact magnesium requirements are difficult to determine, as this depends on various factors (e.g. state of health, diet composition, alcohol consumption, stress, pregnancy / lactation). The dietary reference values used in Germany recommend a daily supply of 350 mg for men and 300 mg for women. The American health authorities, on the other hand, recommend 310 - 320 mg/d for women and 400 - 420 mg/d for men.
In some metabolic situations, the need for magnesium is increased. During lactation, for example, it is significantly higher, i.e. 390 mg/d. Intensive sports activities result in a higher demand for magnesium.
Other causes of increased magnesium demand could include, for example, growth or the use of diuretics and laxatives.
Magnesium deficiency
An important function of magnesium as a physiological calcium antagonist is that it blocks the absorption of calcium by muscle cells, which depends on the ion channel. A magnesium deficit will result in an extracellular ion imbalance between the calcium and magnesium, with the muscle cell becoming constantly excited, which may result in painful muscle contractions. This results in accelerated muscular fatigue as well as muscle hardening and cramps.
Symptoms
Central nervous system and muscles
- Nervous problems (shaking, tingling, numbness, restlessness, dizziness)
- Neuromuscular overexcitation, tremors
- Hyperactivity, impulsivity
- Migraine, headaches
- Cramps in the neck and calf muscles
- Muscle tension
- Sensitivity to noise, low stress tolerance
Gastro-intestinal tract
- Obstipation
- Cramps ("gut cramps")
Cardiovascular system
- Blood circulation problems
- Heart and blood vessel spasms (vascular spasms), especially
- Coronary spasms with tightness of the chest, pain in the heart region, rapid heart beat (tachycardia) and pressure in the heart region.
- Disturbance of the heart rhythm, arrhythmia
In the nervous system, a magnesium deficiency increases nervous excitation via the mechanism as described above, increasing the neuron conduction speed and resulting in nervous problems.
A magnesium deficiency can also result in a lack of perfusion and disturbances of the heart rhythm. Where heart problems occur, the magnesium content of the blood serum should be measured.
In addition, numerous epidemiological studies have shown that people suffering from high blood pressure, arteriosclerosis, heart attacks, osteoporosis or eclampsia frequently also suffer from a magnesium deficiency.
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