People with low levels of magnesium in the diet are more likely to have cardiovascular disease (CVD), and those who take magnesium supplements have lower risk for CVD, according to two new studies. Researchers from the Medical University of South Carolina (MUSC), Charleston, noted that earlier studies showed a link between low magnesium levels and a type of protein (C-reactive protein, or CRP), that signals the acute inflammation doctors believe is a risk factor for CVD.

In the first study, researchers relied on data from the National Health and Nutrition Examination Survey (NHANES), a nationally representative study which has been continuously monitoring the health status of the U.S. population since 1959. The scientists examined the diets of adults aged 17 or older who, from 1999 to 2000, did not take magnesium in supplement form and found that 68% consumed less than the recommended daily allowance (RDA) for magnesium—which for adults is 310 mg to 420 mg per day—and 19% consumed less than half the RDA.

Compared to adults whose diets contained at least the RDA for magnesium, those who consumed less than the RDA were 48% to 75% more likely to have elevated CRP levels. Overweight adults over age 40 who consumed less than half the RDA for magnesium were more than twice as likely (124%) to have elevated CRP levels than were adults whose diets met or exceeded the RDA.

In the second study, the MUSC researchers wanted to gauge CRP levels in those who took magnesium supplements of at least 50 mg per day. Using NHANES data, doctors examined 10,024 adults and found that, from 1999 through 2002, 25.6% took a magnesium supplement of at least 50 mg per day. Those whose total magnesium from all sources was less than the RDA—from diet and/or supplements—were 40% more likely to have elevated CRP compared to those whose diets met the RDA. Among those whose diets had less than half the RDA for magnesium, those who took magnesium supplements were 22% less likely to have elevated CRP than were those who did not take a supplement. Doctors noted that only 21.9% of those who did not take magnesium supplements met the RDA compared to 60.2% of those who took a magnesium supplement.

Reference: Nutrition Research; 2006, Vol. 26, 193-6.

People who have higher calcium and magnesium levels from diet and/or supplements can better absorb sugar (glucose) and convert it to energy (insulin sensitivity) than can those who have lower calcium and magnesium levels. Researchers examined a multiethnic group of 1,036 U.S. adults who took part in the Insulin Resistance Atherosclerosis Study, and who did not have diabetes at the outset of the study in 1992. At the start of the study, and after five years, doctors measured the levels of dairy, calcium, and magnesium in the diet through a food questionnaire, and assessed the level of supplemental calcium and magnesium by reading the supplement labels. The scientists tested insulin sensitivity using a glucose tolerance test and found that those who had more calcium and magnesium from all sources had better insulin sensitivity, and that the effect appeared most reliably in those who had at least 325 mg of magnesium per day.

Reference: American Journal of Epidemiology; 2006, Vol. 164, No. 5, 449-58.

Magnesium supplements strengthened lungs, decreased allergic skin reactions, and reduced the need for medication in children with moderate persistent asthma. Researchers recruited 19 males and 18 females, aged 7 to 19, from a pediatric outpatient clinic and gave 300 mg of magnesium per day or a placebo. All patients also took 250 mcg of fluticasone, a prescription asthma drug, twice per day, and salbutamol, a short-acting, inhaled asthma-spasm medication, when necessary. After two months, researchers testing the magnesium group needed almost twice the amount of a lung-constricting drug (methacholine) to induce a 20% decrease in air expelled from the lung compared to the beginning of the study. The placebo group was unable to improve its response in the methacholine test. Compared to placebo, the magnesium group had an average of 28% fewer days of severe asthma, and reduced the need for salbutamol by almost 40%.

Reference: European Journal of Clinical Nutrition; June 21, 2006.