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OCR for page 485
PART IV: APPENDIX H 485
H
STANDARD DEVIATION OF
REQUIREMENTS FOR
NUTRIENTS WITH AN EAR
Standard Deviation (SD) of requirements is calculated from the Coefficient of
Variation (CV) and the Estimated Average Requirement (EAR) as:
SD = CV ¥ EAR
Basis if not 10 percenta
Nutrient with an EAR CV (percent)
MACRONUTRIENTS
Dietary Carbohydrate 15 Variation in brain glucose
utilization
Protein 12 Skewed distribution; calculated
as half distance from 16th to
84th percentile of protein
requirement distributionb
VITAMINS
Vitamin A 20 Half-life for liver vitamin A
in adults
Vitamin B6 10
Vitamin B12 10
Vitamin C 10
Vitamin E 10
Folate 10
OCR for page 486
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
486
Basis if not 10 percenta
Nutrient with an EAR CV (percent)
Niacin 15 Limited studies suggest greater
variation than 10 percent,
partly from wide variation in
conversion efficiency of
tryptophan to niacin
Riboflavin 10
Thiamin 10
MINERALS
Copper 15 Limited data to set EAR
Iodine 20 Calculation that subtracts out
variation due to experimental
design
Iron Skewed distribution; calculated
by modeling components of
requirement distribution,
estimating the requirement for
absorbed iron at the 97.5
percentile, and with use of an
upper limit of 18 percent iron
absorption, and rounding
Magnesium 10
Molybdenum 15 Limited data to set EAR (few Mo
levels in depletion/repletion
study and small number of
subjects)
Phosphorus 10
Selenium 10
Zinc 10
a The assumption of 10 percent is based on extensive data on the variation in basal
metabolic rate and on a similar CV of 12 percent for protein requirements in adults.
b Rand and colleagues demonstrated that the natural logarithm of requirements in
mg nitrogen/kg/day has a normal distribution with a mean of 4.65 and a standard devia-
tion of 0.12. From this and because the skewness is not extreme, an approximate stan-
dard deviation can be calculated.
