Magnesium is an essential mineral for humans, playing a key role in many biological processes through its function in enzyme activities. For example, those involved in energy production, neuromuscular excitability, muscle contraction, blood coagulation, protein and nucleic acid metabolism. It has been suggested that aging, stress and various diseases may increase magnesium requirements. Inadequate intake and impaired absorption of magnesium are thought to contribute to disorders in humans such as osteoporosis, hypertension and atherosclerotic vascular diseases.
It is recognized that changes in lifestyle since the middle of the 20th century has led to a decrease in dietary magnesium intake. In the USA, it is reported that the dietary intake of magnesium decreased from 450-480 mg/day at the beginning of the 20th century to 185-260 mg/day at the end of the 1980s. Recommended dietary allowances in the USA show 400- 420 mg for men and 310-320 mg for women aged 19-30 years and above 31 years respectively. In most industrialized countries, it has been shown that magnesium intake is below dietary recommendations, due to an increased consumption of refined, fat-rich and processed foods.
Magnesium intake was assessed over a one-year period in 5,448 French volunteers participating in an epidemiological study called SU.VI.MAX. In this cohort, 77% of women and 72% of men had dietary magnesium intake lower than the French recommended dietary allowances (RDAs), i.e. 380 mg for men and 350 mg for women. Furthermore, 23% of women and 18% of men consumed less than two-thirds of RDAs. In Switzerland, the mean daily dietary magnesium intake is 290 mg, with a range of 110- 475 mg/day, while RDAs are 300 and 350 mg/day for men and women respectively.
Magnesium-rich mineral waters provide significant amounts of calorie-free magnesium. It was shown by the SU.VI.MAX study, in which the Water Institute was involved, that natural mineral waters such as Contrex and Vittel Grande Source respectively provided 17% and 7% of total magnesium intake in subjects regularly drinking the two brands. It was also demonstrated earlier from animal experiments that magnesium from Hépar is well absorbed from the intestine and subsequently retained by the body, in particular being incorporated into the bones. However, no data on humans shows the absorption and retention (bioavailability) of magnesium from Hépar or more generally from water. It was one of the objectives of the research program of the Water Institute.
With a content of 110 mg/I of magnesium, Hépar, the mineral water chosen for the study, has the highest magnesium content among all mineral waters sold in France. The objectives of the study, carried out at Nestlé Research Centre (NRC), were first, to evaluate magnesium absorption and retention from drinking Hépar and second, to show whether the simultaneous consumption of a meal with mineral water has an effect on magnesium bioavailability. Magnesium absorption and retention by the body were calculated in 10 healthy women aged 25-45 years with stable isotope techniques. These naturally occurring elements are used as markers to follow the transit of magnesium through the body.
The results demonstrate the bioavailability of magnesium from mineral water in humans. In addition, an enhancement of magnesium absorption was observed when water was consumed with a meal [ from water alone: 45.7 ± 4.6% and with a meal 52.3 ± 3.9%; i.e. a mean absolute increase of the absorption of 6.6%, corresponding to a relative increase of 14.4%]. Magnesium body retention was also significantly higher when water was drunk with meals [ ± 4.2% and 37.4 ± 4.0% retention with and without a meal, respectively; i.e. a mean absolute increase in retention of 4.1%, corresponding to a relative increase of 11.0%].
This increased absorption and retention may be due to a slower gastrointestinal transit time, which enables a better contact of digested food with intestinal cells and/or the presence of products of digestion from meals such as carbohydrates, which may stimulate specific mechanisms of intestinal absorption. In conclusion, the regular consumption of a magnesium-rich mineral water (>50mg/l) would provide a valuable contribution to magnesium requirements. Thus, drinking magnesium-rich water with breakfast or other meals enhances the utilization of magnesium.
The new results were presented at conferences, e.g. that of the Federation of American Societies of Experimental Biology (EB99), Washington, D.C., April 17-21, 1999 (see poster). They have been accepted for publication in the American Journal of Clinical Nutrition (2001).
At the Western Human Nutrition Research Center of the US Department of Agriculture -- one of the most famous teams for mineral and micronutrient research into nutrition, new methods were developed for the determination of magnesium absorption, retention and metabolism in humans. A mathematical model of magnesium metabolism is to be established. It may be useful in detecting chronic magnesium deficiency.
The first part of this study (Preparation and ICP-MS Measurement of Magnesium Stable Isotopes in Human Samples, by M. Sabatier, W.R. Keyes, M.J. Arnaud and J.R. Turnlund) was presented at two congresses (Téma 10, May 2-7, 1999 and International Conference on Stable Isotopes and Isotopic Effects, Carry le Rouet, France, June 20-25, 1999).
This page was first uploaded to The Magnesium Web Site on November 14, 2002