TABLE 5-3 Accretion of Phosphorus (P) in Bone and Lean Tissue of Children Aged 1 to 3 Years Using Growth and Body Composition Data from Fomon et al. (1982)

Gender/Age (y)

Change in Weight (g/y)

Change in Lean (FFBM-osseous) (g/y)

Lean-Tissue Pa (g/y)

Osseous P (g/y)

Bone Pb (g/y)

Total P Gainc (mg/d [mmol/d])

Males

1–2

2,440

1,539

3.54

94

17.8

58 (1.9)

2–3

2,085

2,001

4.60

84

16.0

56 (1.8)

Females

1–2

2,730

2,397

5.51

75

14.2

54 (1.7)

2–3

2,190

1,950

4.48

67

12.7

47 (1.5)

Mean, both sexes

54 (1.7)

NOTE: Based on recent data (Ellis et al., 1997), the daily accretion of phosphorus in bone is calculated from cross-sectional measures of whole body bone mineral content in children. The values are almost identical to those calculated using Fomon et al. (1982) body composition data. Compared were the values listed vertically in the Bone P column above, the data from Ellis yield values of 16 g and 14 g for males, and 15 g and 12 g for females, at the respective ages. This comparability of values obtained by two very different methods gives credence to the method applied for this report in deriving the EARs.

a Assuming a phosphorus content of soft tissue of 0.23 percent.

b Assuming a phosphorus content of bone of 19 percent.

c Calculated from sum of accretion of P in lean and bone/year divided by 365 days.

excretion would be 213 mg (6.9 mmol)/day. At this intake of phosphorus, obligatory losses and predicted accretion values will be generously covered. Phosphorus intakes in excess of this amount would simply lead to increased urinary loss. When urinary excretion is added to the accrued phosphorus of 54 mg (1.74 mmol)/day (Table 5-3), there is a daily need for dietary phosphorus of 267 mg (8.6 mmol)/day.

A conservative estimate of efficiency of phosphorus absorption of 70 percent was used, as suggested for children aged 9 through 18 years, which is slightly higher than the 60 percent figure for adults (Lemann, 1996). No data are available that provide a value for percent efficiency of absorption from the typical mixed diet in early childhood. Using the equation: EAR = (accretion + urinary loss)



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