Determination of the RDA: Ages 19 through 30 Years

The variance in requirements cannot be determined from the data available for either men or women. Thus, a CV of 10 percent is assumed in both cases. This results in an RDA for magnesium in men ages 19 through 30 years of 400 mg (16.7 mmol)/day, and for women ages 19 through 30 years of 310 mg (12.9 mmol)/day.

RDA for Men

19 through 30 years

400 mg (16.7 mmol)/day

RDA for Women

19 through 30 years

310 mg (12.9 mmol)/day

Ages 31 through 50 Years
Indicators Used to Set the EAR in Men

Balance Studies. The results of five balance studies in men aged 31 through 50 years, which met the criteria for inclusion, are shown in Table 6-3. Two controlled-intake studies which looked at the influence of dietary oxalate and fiber on mineral balances, included magnesium balances for men aged 34 to 58 years who were consuming either high-fiber (Kelsay et al., 1979) or high-oxalate (Kelsay and Prather, 1983) diets. Intakes ranged from 308 to 356 mg (12.8 to 14.8 mmol)/day. On a low, nondigestible fiber diet (4.9 g/day), average magnesium balance was positive; but the magnesium intake was not sufficient on the high-fiber or high-oxalate diets to maintain magnesium balance. Magnesium balance in male subjects aged 19 to 64 years given lower magnesium intakes (229 or 258 mg [9.5 or 10.8 mmol]) at two levels of dietary protein has also been estimated (Mahalko et al., 1983). Average magnesium balance at either protein level was at equilibrium for this wider-age-range group, indicating that, at least based on crude magnesium balance, dietary intake was near adequacy overall. However, in another study, magnesium intakes of 240 to 264 mg (10 to 11 mmol)/day resulted in net negative balances (−23 mg [1 mmol]/day and −26 mg [1.1 mmol]/day) in the five subjects studied (Spencer et al., 1994). Magnesium intakes of 789 to 826 mg (32.9 to 34.4 mmol)/day resulted in positive balances in these same subjects. Finally, in a year-long study of magnesium intakes by individuals on self-selected diets with periodic measurements of balance, average intake of seven male subjects aged 35 to 53 years, was 310 ± 88 mg (12.9 ± 3.7 mmol)/day (Lakshmanan et al., 1984). The individual averages of the four 1-week balance periods during the year resulted in a group mean negative magnesium balance, although three subjects had average positive balances or were in equilibrium and four were in negative balance.

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