Magnesium and Health : From the Aspects of Nutrition, Medical Supplies, and Environment

摘要

Magnesium (Mg) has been recognized as an essential element since 1926. The standard daily intake of Mg is 340mg for males and 270 mg for females in Japan. Recently, food customs have changed and consumption of barley and miscellaneous cereals has been reduced. This has resulted in low Mg intake; one of the causes of type 2 diabetes.In north-east Thailand, there has been an endemic health problem of sudden unexplained death syndrome (SUDS); called Lai Tai in the local language. In 1990s our project proceeded to clarify the cause. We assumed it might be due to food customs, and we hypothesized potassium (K) deficiency as a specific cause. But we noticed low levels of Mg in materials analyzed such as salt and the meals of local residents. First we tried analyses of two kinds of rice, regular rice and glutinous rice. Local residents in north-east Thailand consume much glutinous rice. Mg and K concentrations were analyzed according to the cooking process: soaking in water for one night and then steaming. In the case of glutinous rice, Mg concentrations were 41.6% after soaking, and 24.7% after soaking and steaming, compared with the uncooked value. K concentrations were 20.5% after soaking, and 11.7% after soaking and steaming, compared with the uncooked value. These values were lower than the values of regular rice prepared with the same process. Mg and K were similar levels in raw materials. It was clear that much Mg and K were lost during cooking. Then we tried an animal experiment. Mice at 8 weeks old were fed Mg-deficient or Mg/K-deficient diet. Mortality rate was higher in the Mg-deficient group than in the Mg/K-deficient group, and there were no sexual differences. In the Mg/K-deficient group the mortality rate was higher in males than in females. After one week of feeding with the Mg/K-deficient diet, some element concentrations were determined. Plasma Mg concentrations were 1/3 of those of the control, and in spite of this fact, heart muscle and kidney kept normal values in both sexes. The other elements determined were all statistically low in males, except for cobalt, which was higher, but in females molybdenum was lower and iron and cobalt were higher. After feeding a Mg-deficient diet for 2 weeks, testosterone was strongly reduced, but estrogen showed no change. These results suggested that homeostasis ability is lower in males than females, and that the cause of SUDS might correlate with Mg- and/or K- deficiency.