A relevant selection of human and animal studies (years 1990 and later) examining the effectiveness of magnesium intake in providing resilience or treating TBI in the acute phase of injury is presented in Table 12-1. This table elaborates on the treatment methodology and includes review articles on magnesium intake in humans for other central nervous system (CNS) injuries such as subarachnoid hemorrhage, stroke, and hypoxia in the case of human studies. The occurrence or absence of adverse effects in humans is included if reported by the authors.

USES AND SAFETY

The Recommended Dietary Allowance (RDA) for magnesium ranges from 80 mg/day in children between the ages of one and three, to 420 mg/day in males over the age of 30 and 320 mg/day in females over the age of 30. Recommendations for military personnel in garrison training are the same as those for adults over 30 years of age (IOM, 2006). Good dietary sources of magnesium include green leafy vegetables, beans, nuts, seeds, and unrefined whole grains.

According to 2005–2006 data from the National Health and Nutrition Examination Survey (NHANES), just more than half (56 percent) of all individuals aged one year and older had inadequate intakes of magnesium.1 The percentage below the Estimated Average Requirement (EAR) was greatest among 14- to 18-year-olds and adults aged 71 years and over. Two small research studies assessing dietary intake of Army Rangers and Special Forces soldiers in garrison found that approximately 40 percent of these individuals were not meeting the EAR for magnesium, and about 60 percent were not meeting the RDA (IOM, 2006). Although a 2006 analysis found that First Strike Rations and Meals, Ready-to-Eat (MREs) contained sufficient magnesium (IOM, 2006), the Institute of Medicine Committee on Mineral Requirements for Cognitive and Physical Performance of Military Personnel concluded that the information on magnesium status of military personnel in various types of training was too limited to provide evidence of magnesium sufficiency (IOM, 2006).

Magnesium toxicity is not a problem in the context of normal dietary intake. However, intake of magnesium supplements can lead to decreased blood pressure, abdominal cramping, and nausea. These adverse effects have been observed primarily with pharmacological uses of magnesium, rather than intake from food and water. Derived from studies on excessive intake from nonfood sources, the Tolerable Upper Intake Level (UL) of 350 mg/day for individuals nine years of age and over is based on diarrhea as the critical endpoint (IOM, 1997). The risk of magnesium-induced diarrhea mediates against the use of high-dose magnesium supplements. Symptoms of magnesium toxicity are more likely to occur in individuals suffering from renal failure, when the kidney loses its ability to remove excess magnesium (Fleet and Cashman, 2001; IOM, 1997).2

EVIDENCE INDICATING EFFECT ON RESILIENCE

Human Studies

The committee’s review of the literature found no clinical trials investigating the effects of magnesium on resilience for TBI or related diseases or conditions (i.e., subarachnoid hemorrhage, intracranial aneurysm, stroke, anoxic or hypoxic ischemia, or epilepsy). An

1

Available online at http://www.cdc.gov/nchs/nhanes.htm (accessed December 22, 2010).

2

Available online at http://ods.od.nih.gov/factsheets/magnesium/ (accessed December 22, 2010).



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