Dietary magnesium intake has declined in the United States, with a per capita decline of magnesium in the U.S. food supply (estimated as food flowing through the food distribution system) of from 408 mg/day in 1909 to 329 mg/day in 1986, almost a 20% decline. This is believed to be a relatively small decline when compared to many decades earlier when unrefined and unprocessed foods, along with a consumption of less meats and dairy products, were the dietary standard in the U.S. This closely correlates with the chemical analysis of typical U.S. diets in the Food and Drug Administration’s Total Diet Study of 1976, 1977, 1980, 1981 and 1982, and with the United States Department of Agriculture’s 1985 average magnesium intake of adult men, and the USDA’s 1987 mean magnesium intake for adult women. The U.S. decline in dietary magnesium intake is directly attributable to the dietary decrease of unprocessed whole grains, legumes, seeds, and green plant foods, with a concurrent dietary increase of refined and processed foods, meats, sodas, and dairy products.
In those with normal digestion and assimilation, magnesium absorption from food is believed to be from approximately 40 to 60% of that ingested, with a slight reduction in absorption in the presence of phytate (a negatively charged form of phytic acid, i.e., inositol hexaphosphate found in plant leaves) or in the presence of fiber.
Magnesium depletion in humans can occur in those with inadequate dietary intake, excessive calcium intake (which disrupts calcium metabolism), excessive or prolonged levels of stress, gastrointestinal tract abnormalities associated with malabsorption, renal reabsorption dysfunction, excessive fluid and electrolyte losses of systemic or diuretic drug causes, and by the interference of certain drugs.
Large oral intakes of magnesium are generally regarded as safe, with no evidence of harm in those with normal renal function. It is known that excessive oral intakes of magnesium may cause transitory diarrhea.
Oral intakes of magnesium are naturally difficult for the body to absorb. It is believed that only 3 to 12% of elemental magnesium is absorbed for use by the body. Past attempts to increase the amount of magnesium made available for absorption by the body have been only partially successful until the development of compound complex magnesium.
While there is evidence that magnesium chelated with protein amino acids is more effectively absorbed by the body, passing more efficiently through the intestinal membrane into the blood than elemental magnesium, it is not completely clear how much more effective this is. Accordingly, there has been a degree of uncertainty attached to the selection of proper dosages of magnesium prior to the development of compound complex magnesium.