The levels of magnesium in the body are depleted due to a number of factors, such as stress – physical and mental, certain medications (e.g. insulin, diuretics, some asthma medications, birth control pills, corticosteroids), extreme physical training, chemical toxins getting into the body from the environment, excessive intake of sodium chloride (table salt), sugar, caffeine, alcohol, nicotine, cocaine, fizzy drinks (especially colas), intense sweating, diarrhoea, etc. Age is another factor which plays a major role in magnesium deficiency.
This information is quoted from the Office of Dietary Supplements website:
“…There is concern about the prevalence of sub-optimal magnesium stores in the body. For many people, dietary intake may not be high enough to promote an optimal magnesium status, which may be protective against disorders such as cardiovascular disease and immune dysfunction.
The health status of the digestive system and the kidneys significantly influence magnesium status. Magnesium is absorbed in the intestines and then transported through the blood to cells and tissues. Approximately one-third to one-half of dietary magnesium is absorbed into the body. Gastrointestinal disorders that impair absorption such as Crohn’s disease can limit the body’s ability to absorb magnesium. These disorders can deplete the body’s stores of magnesium and in extreme cases may result in magnesium deficiency. Chronic or excessive vomiting and diarrhoea may also result in magnesium depletion.
Healthy kidneys are able to limit urinary excretion of magnesium to compensate for low dietary intake. However, excessive loss of magnesium in urine can be a side effect of some medications and can also occur in cases of poorly-controlled diabetes and alcohol abuse”. http://ods.od.nih.gov/factsheets/magnesium.asp