April 1978
614
The Journal o f P E D I A T R I C S
Plasma amino acid concentrations in newborn infants breast-fed ad libitum Plasma amino acid concentrations were measured in peripheral venous blood of 40 newborn infants breast-fed ad libitum. When these data are compared with amino acid concentrations of umbilical cord artery plasma, only lysine and threonine show a striking decrease after birth; the concentrations of hydroxyproline, asparagine, glutamine, proline, cystine, leucine, tyrosine, and ornithine significantly increase during the first days of life. The high-protein concentration of colostrum and transitional milk may explain this observation.
F r a n k P o h l a n d t , M . D . , Dipl.-Chem., U l m / D o n a u , Federal R e p u b l i c o f G e r m a n y
THE DEVELOPMENT of the brain is not completed at birth, postnatally the brain undergoes a growth spurt. 1 During this time protein deficiency as well as protein overload and hyperaminoacidemia may impair the normal maturation of the brain, resulting in intellectual deficits.2-5 In addition to weight gain and nitrogen retention, therefore, plasma amino acid concentrations should be considered as criteria of optimal nutrition when formulas or amino acid solutions are used in infants. We have suggested that plasma amino acid concentrations of the umbilical artery and of peripheral veins of infants breast-fed ad lib be used as reference values for nutritional studies in infants. ~-~ The present paper reports data on amino acid concentrations in breast-fed newborn infants, in comparison with the previously reported values from the umbilical cord artery. 7, MATERIAL
AND METHODS
Forty healthy term infants born at the Department of Obstetrics and Gynecology of University Hospital Ulm were studied. The infants were breast-fed ad libitum, receiving no additional formula within 24 hours before From the Section of Neonatology, Department of Pediatrics, University of Ulm. Presented in part at the annual meeting, European Society for Pediatric Research, June 20-24, 1976, Rotterdam. Supported by Deutsche Forschungsgemeinschaft, SFB 87, Projekt D5. Reprint address: Universitaets-Kinderklinik, ,grittwitzstrasse 43, D-7900 Ulm/Donau, Federal Republic of Germany.
Vol. 92, No. 4, pp. 614-616
blood was drawn. The milk intake was determined to the nearest 10 gm by weighing the infants before and after nursing. One milliliter of blood was drawn from a carpal or cubital vein into heparinized tubes at variable time intervals from the last feeding, between 9:30 AM and 12 noon. The samples were analyzed by ion exchange column chromatography, as previously reported. ~ The Mann-Whitney rank sum test was used to validate differences between samples. Percentiles were calculated according to Herrera? RESULTS
The values of plasma amino acids of peripheral venous blood taken from nonfasting healthy term infants breastfed ad lib between one and 21 days of age are recorded in Table I. A further analysis o f these data was done to disclose any possible influence of the volume of ingested milk, the time interval between feeding and drawing blood, the age, and the birth weight on the amino acid concentrations. The group of infants receiving a lower milk intake (median 85 ml/kg/day) had no significant differences in the concentrations of most amino acids compared with those (n = 22) who had a higher milk intake (median 121 ml/kg/day) and were older. Since the blood samples were taken shortly after nursing (median 90 minutes, n = 23), the concentrations of most amino acids were slightly higher than in the group of infants in whom blood was taken after a longer time span (median 150 mintues) subsequent to the last feeding, but this difference was significant for isoleucine only. The younger group
0022-3476/78/0492-0614500.30/0 9 1978 The C. V. Mosby Co.
Volume 92 Number 4
Plasma concentrations in breast-fed newborn infants
6 15
Table I. Plasma amino acid values in breast-fed newborn infants (/~mol/1)
I Amino acid Taurine Urea Hydroxyproline Threonine Serine Asparagine Gtutamic acid Glutamine a-NH2-adipic acid Proline Gtycine Alanine Citrulline a-NH2-n-butyric acid Valine Cystine Methionine Cystathionine Isoleucine Leucine Tyrosine Phenylalanine Tryptophan Ornithine Lysine Histidine 3-Methylhistidine Arginine Birthweight (gm) Gestational age (wk) Age (days) Milk intake (gm/kg body weight day) Time from last feeding to taking blood (min) ND
n 40 40 37 40 40 38 22 38 34 40 40 40 37 40 40 39 40 33 40 40 40 40 27 40 40 40 35 38
Minimum value
Tenth percentile
19 900 18 65 62 36 30 243 ND 144 106 132 3.4 3.9 78 26 6.3 0.3 27 61 32 16 17 38 71 32 0.3 17 2,430 38 0.7 25
27 1,000 28 76 80 43 36 468 ND 162 120
0
Median
5.8 7.8 108 34 13 0.4 32 73 45 23 25 49 92 44 0.7 30 3,100 38.8 3.4 72
50 2,300 40 104 109 53 56 610 ND 212 183 235 13 14 153 52 20 1.0 49 103 72 41 44 84 148 66 3.0 47 3,595 40 4.4 103
30
115
163
Ninetieth percen tile
Maxim um value
96 4,600 55 134 143 87 98 755 ND 283 228
265 13,000 72 147 161 191 103 822 ND 329 254
387
455
20 21 184 62 29 3.1 71 160 117 63 69 116 210 85 5.4 84 3,940 42 7.5 137
36 24 264 71 36 5.5 80 183 124 71 71 207 272 107 5.9 119 4,110 43 20.9 168
191
240
= Not detected.
(median 4.2 days, n = 26) had a significantly lower milk intake (median 93 m l / k g / d a y ) , yet had amino acid concentrations similar to those in the older group. Furthermore, we found no influence of birth weight on the plasma amino acid concentrations. DISCUSSION Our data on plasma a m i n o acid values in breast-fed infants may be compared with the published values for umbilical cord artery after elective cesarean section determined in our laboratory by the same analytical m e t h o d ? The comparison of the median values shows that postnatally there is a marked decrease of lysine ( - 9 3 /~mol/1) and threonine ( - 8 9 / ~ m o l / 1 ) only in infants breast-fed ad lib. Phenylalanine values also fall slightly but significantly (--7 /~mol/1), as do those for histidine ( - 2 3 /~mol/1,
P < 0.01). The concentrations of the other amino acids, however, do not decrease; those of hydroxyproline, asparagine, glutamine, proline, cystine, leucine, tyrosine, and ornithine even increase significantly (P < 0.01), if one compares the plasma concentrations of amino acids in peripheral venous blood of nonfasting breast-fed infants, 4 and 5 days of age, with the concentrations in umbilical cord artery plasma. This group (n = 26) was choosen for statistical reason, i.e., to obtain samples of equal size. The presented results could be used as reference values for nutritional studies in newborn infants. Moreover, equal levels of plasma amino acids in the umbilical artery at term and in peripheral veins of newborn infants breastfed ad lib have been established. The reported dose of amino acids required for maintenance of amino acids at the levels o f the umbilical cord artery, 8 therefore, could be
6 16
Pohlandt
used as a guideline in parenteral nutrition of newborn infants. Our results seem to conflict with the data of Lindblad and Baldesten. TM These authors studied the amino acid concentrations in venous plasma o f five term newborn infants receiving breast milk at 24 and 72 hours o f age, three to four hours after the last meal. A decrease of all amino acid values was found, except for glycine. These results are in good agreement with data on newborn infants receiving a hypocaloric infusion of a carbohydrate-electrolyte solution? The marked drop o f the essential amino acids and the increase of glycine which these authors found was also observed subsequent to protein deficiency.", 12 Perhaps the infants studied by Lindblad and Baldesten were in a somewhat fasting state. In fact, these authors gave no information on the amount of milk intake and the kind of breast milk. Since they c o m m e n t e d on adoption cases, it seems possible that their infants received pooled breast milk rather than their mother's milk. The protein content of breast milk decreases during lactation~:~. 44; colostrum contains 2.1 to 2.0 g m / d l protein and mature milk 0.8 to 0.9 gm/dl. This difference, aside from possibly different volumes of ingested milk, likely explains the seemingly conflicting results. Ghadimi and Pecora 1~ rePorted amino acid concentrations in term newborn infants quite similar to our o w n ? ~ After a decrease on the second day they observed an increase of most amino acids above the range of cord blood at the fifth and ninth day of age, except for lysine and threonine. A detailed comparison, however, is hampered by the lack of data on milk intake and protein content of the evaporated milk formula ingested by their subjects. The amount of protein supplied to newborn infants depends on the volume and protein concentration of the milk. Despite a striking increase of milk intake during the first days of life, the amount of protein ingested changes only slightly because of the simultaneous decrease of protein concentration. In breast-fed newborn infants the high-protein concentration of colostrum effects an appropriate protein supply despite the low volume ingested during the first days of life. it may be speculated that nature in this way ensures a continuity of plasma amino acid concentrations before and after birth.
The Journal of Pediatrics April 1978
I gratefully appreciate the technical assistance of Ms. O. Seitz and the secreterial help of Ms. H. Stfitzle. REFERENCES
1. Dobbing J: The later development of the brain and its vulnerability, in Davis JA, and Dobbing J, editors: Scientific foundations of paediatrics, London, 1974, Heinemann Medical Books. 2. Chase HP: The effects of intrauterine and postnatal undernutrition on normal brain development, Ann NY Acad Sci 205:231, 1973. 3. Stoch MB, and Smythe PM: 15-year developmental study on effects of severe undernutrition during infancy on subsequent physical growth and intellectual functioning, Arch Dis Child 51"327, 1976. 4. Menkes JH, Welcher DW, Levi HS, et al: Relationship of elevated blood tyrosine to the ultimate intellectual performance of premature infants, Pediatrics 49:218, 1972. 5. Mammunes P, Prince PE, Thornton NH, et al: Intellectual deficits after transient tyrosinemia in the term neonate, Pediatrics 57:675, 1976. 6. Pohlandt F: Zur Vermeidung yon Aminos~iurenimbalanzen bei Neugeborenen mit parenteraler Ern~hrung, Monatschr Kinderheitkd 123:448, 1975. 7. Pohlandt F: Reference values of plasma amino acid concentrations during parenterat nutrition in premature newborns and infants, Pediatr Res 11:891, 1976 (abstr). 8. Pohlandt F: Plasma amino acid concentrations in umbilical cord vein and artery of newborn infants after elective cesarean section or spontaneous delivery, J PEDIATR.92:617, 1978. 9. Herrera L: The precision of percentiles in establishing normal limits in medicine, J Lab Clin Med 52:34, 1958. 10. Lindblad BS, and Baldesten A: Time studies on free amino acid levels of venous plasma during the neonatal period, Acta Paediatr Scand 58:252, 1969. 11. Saunders SJ, Truswell AS, Barbezat GO, et al: Plasma free aminoacid pattern in protein-calorie malnutrition, Lancet 2:795, 1967. 12. Snyderman SE, Holt LE, Norton PM, et al: The plasma aminogram. I. Influence of the level of protein intake and a comparison of whole protein and amino acid diets, Pediatr Res 2:131, 1968. 13. Agarwal KN, Khurana V, and Agarwal DK: Protein and free amino acids content of human milk, Ind Pediatr 12:4t5, 1975. 14. L6nnerdal B, Forsum E, and Hambraeus L: A longitudinal study of the protein, nitrogen, and lactose contents of human milk from Swedish well-nourished mothers, Am J Clin Nutr 29:1127, 1976. 15. Ghadimi H, and Pecora P: Plasma amino acids after birth, Pediatrics 33:182, 1964.
614
The Journal o f P E D I A T R I C S
Plasma amino acid concentrations in newborn infants breast-fed ad libitum Plasma amino acid concentrations were measured in peripheral venous blood of 40 newborn infants breast-fed ad libitum. When these data are compared with amino acid concentrations of umbilical cord artery plasma, only lysine and threonine show a striking decrease after birth; the concentrations of hydroxyproline, asparagine, glutamine, proline, cystine, leucine, tyrosine, and ornithine significantly increase during the first days of life. The high-protein concentration of colostrum and transitional milk may explain this observation.
F r a n k P o h l a n d t , M . D . , Dipl.-Chem., U l m / D o n a u , Federal R e p u b l i c o f G e r m a n y
THE DEVELOPMENT of the brain is not completed at birth, postnatally the brain undergoes a growth spurt. 1 During this time protein deficiency as well as protein overload and hyperaminoacidemia may impair the normal maturation of the brain, resulting in intellectual deficits.2-5 In addition to weight gain and nitrogen retention, therefore, plasma amino acid concentrations should be considered as criteria of optimal nutrition when formulas or amino acid solutions are used in infants. We have suggested that plasma amino acid concentrations of the umbilical artery and of peripheral veins of infants breast-fed ad lib be used as reference values for nutritional studies in infants. ~-~ The present paper reports data on amino acid concentrations in breast-fed newborn infants, in comparison with the previously reported values from the umbilical cord artery. 7, MATERIAL
AND METHODS
Forty healthy term infants born at the Department of Obstetrics and Gynecology of University Hospital Ulm were studied. The infants were breast-fed ad libitum, receiving no additional formula within 24 hours before From the Section of Neonatology, Department of Pediatrics, University of Ulm. Presented in part at the annual meeting, European Society for Pediatric Research, June 20-24, 1976, Rotterdam. Supported by Deutsche Forschungsgemeinschaft, SFB 87, Projekt D5. Reprint address: Universitaets-Kinderklinik, ,grittwitzstrasse 43, D-7900 Ulm/Donau, Federal Republic of Germany.
Vol. 92, No. 4, pp. 614-616
blood was drawn. The milk intake was determined to the nearest 10 gm by weighing the infants before and after nursing. One milliliter of blood was drawn from a carpal or cubital vein into heparinized tubes at variable time intervals from the last feeding, between 9:30 AM and 12 noon. The samples were analyzed by ion exchange column chromatography, as previously reported. ~ The Mann-Whitney rank sum test was used to validate differences between samples. Percentiles were calculated according to Herrera? RESULTS
The values of plasma amino acids of peripheral venous blood taken from nonfasting healthy term infants breastfed ad lib between one and 21 days of age are recorded in Table I. A further analysis o f these data was done to disclose any possible influence of the volume of ingested milk, the time interval between feeding and drawing blood, the age, and the birth weight on the amino acid concentrations. The group of infants receiving a lower milk intake (median 85 ml/kg/day) had no significant differences in the concentrations of most amino acids compared with those (n = 22) who had a higher milk intake (median 121 ml/kg/day) and were older. Since the blood samples were taken shortly after nursing (median 90 minutes, n = 23), the concentrations of most amino acids were slightly higher than in the group of infants in whom blood was taken after a longer time span (median 150 mintues) subsequent to the last feeding, but this difference was significant for isoleucine only. The younger group
0022-3476/78/0492-0614500.30/0 9 1978 The C. V. Mosby Co.
Volume 92 Number 4
Plasma concentrations in breast-fed newborn infants
6 15
Table I. Plasma amino acid values in breast-fed newborn infants (/~mol/1)
I Amino acid Taurine Urea Hydroxyproline Threonine Serine Asparagine Gtutamic acid Glutamine a-NH2-adipic acid Proline Gtycine Alanine Citrulline a-NH2-n-butyric acid Valine Cystine Methionine Cystathionine Isoleucine Leucine Tyrosine Phenylalanine Tryptophan Ornithine Lysine Histidine 3-Methylhistidine Arginine Birthweight (gm) Gestational age (wk) Age (days) Milk intake (gm/kg body weight day) Time from last feeding to taking blood (min) ND
n 40 40 37 40 40 38 22 38 34 40 40 40 37 40 40 39 40 33 40 40 40 40 27 40 40 40 35 38
Minimum value
Tenth percentile
19 900 18 65 62 36 30 243 ND 144 106 132 3.4 3.9 78 26 6.3 0.3 27 61 32 16 17 38 71 32 0.3 17 2,430 38 0.7 25
27 1,000 28 76 80 43 36 468 ND 162 120
0
Median
5.8 7.8 108 34 13 0.4 32 73 45 23 25 49 92 44 0.7 30 3,100 38.8 3.4 72
50 2,300 40 104 109 53 56 610 ND 212 183 235 13 14 153 52 20 1.0 49 103 72 41 44 84 148 66 3.0 47 3,595 40 4.4 103
30
115
163
Ninetieth percen tile
Maxim um value
96 4,600 55 134 143 87 98 755 ND 283 228
265 13,000 72 147 161 191 103 822 ND 329 254
387
455
20 21 184 62 29 3.1 71 160 117 63 69 116 210 85 5.4 84 3,940 42 7.5 137
36 24 264 71 36 5.5 80 183 124 71 71 207 272 107 5.9 119 4,110 43 20.9 168
191
240
= Not detected.
(median 4.2 days, n = 26) had a significantly lower milk intake (median 93 m l / k g / d a y ) , yet had amino acid concentrations similar to those in the older group. Furthermore, we found no influence of birth weight on the plasma amino acid concentrations. DISCUSSION Our data on plasma a m i n o acid values in breast-fed infants may be compared with the published values for umbilical cord artery after elective cesarean section determined in our laboratory by the same analytical m e t h o d ? The comparison of the median values shows that postnatally there is a marked decrease of lysine ( - 9 3 /~mol/1) and threonine ( - 8 9 / ~ m o l / 1 ) only in infants breast-fed ad lib. Phenylalanine values also fall slightly but significantly (--7 /~mol/1), as do those for histidine ( - 2 3 /~mol/1,
P < 0.01). The concentrations of the other amino acids, however, do not decrease; those of hydroxyproline, asparagine, glutamine, proline, cystine, leucine, tyrosine, and ornithine even increase significantly (P < 0.01), if one compares the plasma concentrations of amino acids in peripheral venous blood of nonfasting breast-fed infants, 4 and 5 days of age, with the concentrations in umbilical cord artery plasma. This group (n = 26) was choosen for statistical reason, i.e., to obtain samples of equal size. The presented results could be used as reference values for nutritional studies in newborn infants. Moreover, equal levels of plasma amino acids in the umbilical artery at term and in peripheral veins of newborn infants breastfed ad lib have been established. The reported dose of amino acids required for maintenance of amino acids at the levels o f the umbilical cord artery, 8 therefore, could be
6 16
Pohlandt
used as a guideline in parenteral nutrition of newborn infants. Our results seem to conflict with the data of Lindblad and Baldesten. TM These authors studied the amino acid concentrations in venous plasma o f five term newborn infants receiving breast milk at 24 and 72 hours o f age, three to four hours after the last meal. A decrease of all amino acid values was found, except for glycine. These results are in good agreement with data on newborn infants receiving a hypocaloric infusion of a carbohydrate-electrolyte solution? The marked drop o f the essential amino acids and the increase of glycine which these authors found was also observed subsequent to protein deficiency.", 12 Perhaps the infants studied by Lindblad and Baldesten were in a somewhat fasting state. In fact, these authors gave no information on the amount of milk intake and the kind of breast milk. Since they c o m m e n t e d on adoption cases, it seems possible that their infants received pooled breast milk rather than their mother's milk. The protein content of breast milk decreases during lactation~:~. 44; colostrum contains 2.1 to 2.0 g m / d l protein and mature milk 0.8 to 0.9 gm/dl. This difference, aside from possibly different volumes of ingested milk, likely explains the seemingly conflicting results. Ghadimi and Pecora 1~ rePorted amino acid concentrations in term newborn infants quite similar to our o w n ? ~ After a decrease on the second day they observed an increase of most amino acids above the range of cord blood at the fifth and ninth day of age, except for lysine and threonine. A detailed comparison, however, is hampered by the lack of data on milk intake and protein content of the evaporated milk formula ingested by their subjects. The amount of protein supplied to newborn infants depends on the volume and protein concentration of the milk. Despite a striking increase of milk intake during the first days of life, the amount of protein ingested changes only slightly because of the simultaneous decrease of protein concentration. In breast-fed newborn infants the high-protein concentration of colostrum effects an appropriate protein supply despite the low volume ingested during the first days of life. it may be speculated that nature in this way ensures a continuity of plasma amino acid concentrations before and after birth.
The Journal of Pediatrics April 1978
I gratefully appreciate the technical assistance of Ms. O. Seitz and the secreterial help of Ms. H. Stfitzle. REFERENCES
1. Dobbing J: The later development of the brain and its vulnerability, in Davis JA, and Dobbing J, editors: Scientific foundations of paediatrics, London, 1974, Heinemann Medical Books. 2. Chase HP: The effects of intrauterine and postnatal undernutrition on normal brain development, Ann NY Acad Sci 205:231, 1973. 3. Stoch MB, and Smythe PM: 15-year developmental study on effects of severe undernutrition during infancy on subsequent physical growth and intellectual functioning, Arch Dis Child 51"327, 1976. 4. Menkes JH, Welcher DW, Levi HS, et al: Relationship of elevated blood tyrosine to the ultimate intellectual performance of premature infants, Pediatrics 49:218, 1972. 5. Mammunes P, Prince PE, Thornton NH, et al: Intellectual deficits after transient tyrosinemia in the term neonate, Pediatrics 57:675, 1976. 6. Pohlandt F: Zur Vermeidung yon Aminos~iurenimbalanzen bei Neugeborenen mit parenteraler Ern~hrung, Monatschr Kinderheitkd 123:448, 1975. 7. Pohlandt F: Reference values of plasma amino acid concentrations during parenterat nutrition in premature newborns and infants, Pediatr Res 11:891, 1976 (abstr). 8. Pohlandt F: Plasma amino acid concentrations in umbilical cord vein and artery of newborn infants after elective cesarean section or spontaneous delivery, J PEDIATR.92:617, 1978. 9. Herrera L: The precision of percentiles in establishing normal limits in medicine, J Lab Clin Med 52:34, 1958. 10. Lindblad BS, and Baldesten A: Time studies on free amino acid levels of venous plasma during the neonatal period, Acta Paediatr Scand 58:252, 1969. 11. Saunders SJ, Truswell AS, Barbezat GO, et al: Plasma free aminoacid pattern in protein-calorie malnutrition, Lancet 2:795, 1967. 12. Snyderman SE, Holt LE, Norton PM, et al: The plasma aminogram. I. Influence of the level of protein intake and a comparison of whole protein and amino acid diets, Pediatr Res 2:131, 1968. 13. Agarwal KN, Khurana V, and Agarwal DK: Protein and free amino acids content of human milk, Ind Pediatr 12:4t5, 1975. 14. L6nnerdal B, Forsum E, and Hambraeus L: A longitudinal study of the protein, nitrogen, and lactose contents of human milk from Swedish well-nourished mothers, Am J Clin Nutr 29:1127, 1976. 15. Ghadimi H, and Pecora P: Plasma amino acids after birth, Pediatrics 33:182, 1964.
