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TABLE 3-1 Illustration of Observed Mean Intakes of Magnesium That Would Be Necessary to Have 85 Percent or 97.5 Percent Confidence That Usual Intake Is Greater Than the Requirement for a Woman 40 Years of Age

 

Using SD of Intake from CSFIIa

Assuming the SD is 25 Percent Larger

Assuming the SD is 50 Percent Larger

 

mg

% RDAb

mg

% RDA

mg

% RDA

Magnesium EARc

265

 

265

 

265

 

SD of requirement

26.5

 

26.5

 

26.5

 

Magnesium RDA

320

 

320

 

320

 

Assumed SD of intaked

86

 

107

 

129

 

Observed mean intake with 85 % confidence of adequacy of usual intake

1 d of intake

355

111

376

117

397

124

3 d of intake

321

100

332

104

344

107

7 d of intake

307

96

313

98

320

100

Observed mean intake with 97.5 % confidence of adequacy of usual intake

1 d of intake

445

139

486

152

528

165

3 d of intake

377

118

400

125

423

132

7 d of intake

349

109

362

113

376

117

NOTE: Observed mean intake with xx percent confidence of adequacy = observed mean intake necessary to have approximately xx percent confidence that the woman's intake is greater than her requirement.

aSD = standard deviation; CSFII = Continuing Survey of Food Intake by Individuals.

b RDA = Recommended Dietary Allowance for women 31 through 50 years of age

c EAR = Estimated Average Requirement for women 31 through 50 years of age.

dSD of magnesium intake for women 19 through 50 years of age taken from CSFII (Appendix Table B-2).

is not the best estimate of the individual's SD of daily intake, the Subcommittee still recommends its use in individual assessment.

Table 3-1 expands this example to further illustrate the effect of day-to-day variation on the evaluation of magnesium intake for a woman in the 31–50 years age group.

  • For a given confidence level, the number of days of intake data affects the level of nutrient intake judged to be adequate. Based on the SD in intake of 85.9 mg/day for an individual (again using the information in Appendix Table B-2), observed intake would need



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