Amino Acid Requirement for Infants and Children

The 9 indispensable amino acids need to be obtained from the diet and, therefore, requirements have been defined for them. The amino acid requirements (AI) for young infants (0–6 months) are based on average human milk intake of 0.78 liters/day and the mean content of each indispensable amino acid in human milk (table 3).

The EAR for IAA in older infants (7–12 months) and children (1–18 years) are calculated using the factorial method (table 4). The method assumes that the maintenance requirement for each IAA is similar to adults and the requirements differ in children only by the growth needs. The requirement for growth is estimated from the rate of protein deposition, amino acid composition of whole body protein and the efficiency of protein utilization.

Recently we provided evidence that the maintenance requirements for adults and children are similar [6–8]. For a detailed review on the methods to determine amino acid requirements refer to Pencharz and Ball [9].

The conditionally indispensable amino acids (table1) are those that the infant or child is unable to produce in sufficient amounts and hence all or part of the daily needs for those amino acids must be provided by the diet.
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Key Messages

Diet must contain a balanced mixture of all amino acids.

This can most easily be achieved by daily ingestion of animal protein: an alternative is a complementary mixture of plant proteins.

Table 3. Indispensable amino acid requirements for young infants at 0–6 months of age

 

Adequate intake mg/kg per day Intake per day mg/day
 
Histidine
Isoleucine
Leucine
Lysine
Methionine + cysteine
Phenylalanine + tyrosine
Threonine
Tryptophan
Valine
36
88
156
107
59
135
73
28
87
214
529
938
640
353
807
436
167
519
Data from Dietary Reference Intakes 2002/2005 [3]. Adequate intake calculated from the average volume of human milk intake and the mean indispensable amino acid content of human milk.

Table 4. Indispensable amino acid requirement for older infants, children and adolescents

Age Average requirement (EAR) mg/kg per day Safe level of intake (RDA) mg/kg per day
7-12 months
Histidine
Isoleucine
Leucine
Lysine
Methionine + cysteine
Phenylalanine + tyrosine
Threonine
Tryptophan
Valine

22
30
65
62
30
58
34
 9
39

32
43
93
89
43
84
49
13
58
1–3 years
Histidine
Isoleucine
Leucine
Lysine
Methionine + cysteine
Phenylalanine + tyrosine
Threonine
Tryptophan
Valine

16
22
48
45
22
41
24
 6
28

21
28
63
58
28
54
32
 8
37
4–8 years
Histidine
Isoleucine
Leucine
Lysine
Methionine + cysteine
Phenylalanine + tyrosine
Threonine
Tryptophan
Valine

13
18
40
37
18
33
19
 5
23

16
22
49
46
22
41
24
 6
28
9–13 years, boys
Histidine
Isoleucine
Leucine
Lysine
Methionine + cysteine
Phenylalanine + tyrosine
Threonine
Tryptophan
Valine

13
18
40
37
18
33
19
 5
23

17
22
49
46
22
41
24
 6
28
 
Age Average requirement (EAR) mg/kg per day Safe level of intake (RDA) mg/kg per day
9-13 years, girls
Histidine
Isoleucine
Leucine
Lysine
Methionine + cysteine
Phenylalanine + tyrosine
Threonine
Tryptophan
Valine

12
17
38
35
17
31
18
 5
22

15
21
47
43
21
38
22
 6
27
14-18 years, boys
Histidine
Isoleucine
Leucine
Lysine
Methionine + cysteine
Phenylalanine + tyrosine
Threonine
Tryptophan
Valine

12
17
38
35
17
31
18
 5
22

15
21
47
43
21
38
22
 6
27
14-18 years, girls
Histidine
Isoleucine
Leucine
Lysine
Methionine + cysteine
Phenylalanine + tyrosine
Threonine
Tryptophan
Valine

12
16
35
32
16
28
17
 4
20

14
19
44
40
19
35
21
 5
24
Data from Dietary Reference Intakes 2002/2005 [3]. EAR = Estimated average requirement, calculated from maintenance + growth (rate of protein deposition x efficiency of protein utilization); RDA = recommended dietary allowance, calculated from EAR + 2 x SD of EAR.