In the United States, however, the average daily magnesium intake is about 320 mg for men and about 230 mg for women, or 24% and 28%, respectively, below the RDAs. A recent study showed that elderly American men and women consume only about 225 and 166 mg/day of magnesium, respectively, or 46% and 48% below the RDAs.or adults aged 31 or older, the Food and Nutrition Board of the Institute of Medicine has set the Recommended Dietary Allowance (RDA) for magnesium at 420 mg/day for men and 320 mg/day for women (for adults aged 19–30, the figures are 400 and 310, respectively).