Magnesium absorption from mineral water

Intestinal Absorption and Factors Influencing Bioavailability of Magnesium-An Update

Background:

Information on the bioavailability of the essential mineral Mg2+ is sparse.

Objective/Method:

Evaluation of the present knowledge on factors influencing the bioavailability and intestinal absorption of Mg2+.

Results:

Mg2+ is absorbed via a paracellular passive and a transcellular active pathway that involves TRPM6/7 channel proteins. The bioavailability of Mg2+ varies within a broad range, depending on the dose, the food matrix, and enhancing and inhibiting factors. Dietary factors impairing Mg2+ up-take include high doses of other minerals, partly fermentable fibres (e.g., hemicellulose), non-fermentable fibres (e.g., cellulose, lignin), phytate and oxalate, whereas proteins, medium-chain-triglycerides, and low- or indigestible carbohydrates (e.g., resistant starch, oligosaccharides, inulin, mannitol and lactulose) enhance Mg2+ uptake. The Mg2+ dose is a major factor controlling the amount of Mg2+ absorbed. In principle, the relative Mg2+ uptake is higher when the mineral is in-gested in multiple low doses throughout the day compared to a single, large intake of Mg2+. The type of Mg2+ salt appears less relevant than is often thought. Some studies demonstrated a slightly higher bioavailability of organic Mg2+ salts compared to inorganic compounds under standardized conditions, whereas other studies did not.

Conclusion:

Due to the lack of standardized tests to assess Mg2+ status and intestinal absorption, it remains unclear which Mg2+ binding form produces the highest bioavailability. The Mg2+ intake dose combined with the endogenous Mg2+ status is more important. Because Mg2+ cannot be stored but only retained for current needs, a higher absorption is usually followed by a higher excretion of the mineral.

Magnesium absorption from mineral waters of different magnesium content in healthy subjects

OBJECTIVE

To assess the absorption of magnesium (Mg) from mineral waters of different Mg content in comparison to low mineralized water and a Mg capsule.

MATERIALS AND METHODS

DESIGN

Randomized, controlled, double- blind trial in a crossover design with an additional control with a Mg capsule.

SETTING

Institute of Balneology and Medical Climatology, Medical School of Hanover, Germany.

SUBJECTS

22 healthy male volunteers aged between 23-46 years.

INTERVENTION

After a standardized breakfast, each participant received, in Latin square order, 500 ml of either of two Mg-rich mineral waters (281 or 120 mg/l). As a control condition, a mineral water of low Mg content (8 mg/l) was used. A Mg capsule (Magnesium-Diasporal 150, Protina, Ismaning, Germany) was used for further comparisons.

RESULTS

Changes in serum Mg levels in the first 4 hours after intake differed significantly between the groups (p = 0.030; ANOVA). Mean values differed between the Mg-rich mineral water conditions and the control conditions though did not reach statistical significance (p = 0.055), however, mean values did not differ between the test waters and the capsule (p = 0.338).

CONCLUSION

Magnesium from mineral waters can easily be absorbed and its absorption rate is similar to that from a pharmaceutical Mg preparation.

Small bowel absorption of magnesium and calcium sulphate from a natural mineral water in subjects with ileostomy

BACKGROUND

In many developed countries, magnesium and calcium intakes do not reach recommendations for a large part of the population. Mineral water may be a useful alternative source of dietary minerals, especially in groups of people at risk for developing deficiency due to low intakes.

AIM

To assess if the addition of a natural and mineral-rich water increased small bowel mineral absorption in people with ileostomy.

METHODS

A controlled randomised crossover study with two periods of two days each and a minimum 5 days of washout was performed in six ileostomy subjects. Apparent mineral absorption from 0.5 L of natural mineral water with either a high or a low mineral content consumed in the fasting state was compared. The daily addition of minerals corresponded to 2.3mmol magnesium, 6.9 mmol calcium and 7.7mmol sulphate. Ileostomy effluents were sampled and analysed for magnesium, calcium and total sulphate.

RESULTS

When compared with the control, the median absorbed amount of magnesium increased from 0.8 (0-1.34) mmol/d to 1.2 (0.8-1.9) mmol/d,which corresponded to a 30% increase (P = 0.028). Median amount of calcium absorbed increased from 8.3 (6.7-13.6) mmol/d to 14.8 (8.3-20.4) mmol/d, i. e. a 45% increase (P = 0.027). The sulphate absorption increased from 1.9 (1.3-2.2) mmol/d to 5.1 (4.2-6.8) mmol/d,which corresponded to 197 % increase (P = 0.028).

CONCLUSIONS

The mineral-rich water increased absorption of both magnesium and calcium and can therefore be used as an additional source of minerals. However, consumption with meals may be preferred.