Adequacy and safety of α-lactalbumin–enriched low-protein infant formula: A randomized controlled trial

Nutrition 74 (2020) 110728

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Applied nutritional investigation

Adequacy and safety of a-lactalbumin
enriched low-protein infant formula: A randomized controlled trial Hanna Petersen M.D., M.Sc. a,*, Antonia Nomayo M.D. a, Richard Zelenka Ph.D. b, Janine Foster a, Josef Tvrdí k Ph.D. c, Frank Jochum M.D. a a b c

Department of Pediatrics, Evangelisches Waldkrankenhaus Spandau, Berlin, Germany DMK Baby GmbH, Bremen, Germany Department of Computer Sciences, University of Ostrava, Czech Republic

A R T I C L E

I N F O

Article History: Received 2 July 2019 Received in revised form 8 January 2020 Accepted 12 January 2020 Keywords: Infant formula Low protein a-lactalbumin Growth Weight gain

A B S T R A C T

Objectives: The aim of this study was to demonstrate suitability and safety of an infant formula enriched with a-lactalbumin with a reduced protein content of 1.89 g protein/100 kcal. Methods: This was a randomized, double-blind controlled trial with 80 healthy newborn infants who were assigned to receive either an isocaloric low- or high-protein content formula (1.89 versus 2.1 g/100 kcal). The low-protein content formula was enriched with a-lactalbumin. A breast-fed reference group of 40 infants was studied concurrently. Anthropometric measures were taken at inclusion, after 6 and 12 wk as well as after 6 and 12 mo of follow-up. Primary outcome was weight gain in g/d between study inclusion to 12 wk. Secondary outcomes included anthropometric measures expressed in Z-scores, mean formula consumption, and caloric intake as well as food tolerance. Results: Fifty-two infants in the formula group (low protein: 26, high protein: 26) and 32 in the breast-fed reference group completed the 3-mo intervention period. There was no difference in weight gain among feeding groups at the end of the intervention period. Mean weight gain in g/d was 32 in the low-protein, 31 in the high-protein, and 33 in the breast-fed reference group. No significant difference was found between study groups in Z-scores for weight, length, head circumference, weight-for-length, or body mass index nor for fat percentage at end of intervention and after follow-up. Conclusion: a-lactalbumin
enriched formula with a protein content of 1.89 g protein/100 kcal is safe and supports adequate growth. © 2020 Elsevier Inc. All rights reserved.

This study was sponsored by Humana/DMK Baby GmbH, Germany: supply of study formula and funding of study personnel as well as study grants. The sponsor was involved in study design as well as in critical reading of the manuscript and the decision to submit the article for publication. There was no sponsor involvement in the collection, analysis, or interpretation of data. HP reports honoraria from Humana GmbH and nonfinancial support from Humana GmbH. AN reports personal fees from Humana GmbH during the preliminary stages of the study, as well as honoraria and non-financial support from Humana GmbH outside the submitted work. RZ is an employee of DMK Baby GmbH. JT has nothing to declare. FJ reports grants, personal fees, and non-financial support from DMK Baby GmbH, Bremen, Germany, during the conduct of the study; personal fees and non-financial support from Nestle Nutrition, personal fees and nonfinancial support from Fresenius Kabi, personal fees and non-financial support from Humana (DMK Baby), outside the submitted work. In addition, FJ has a patent for a needle for blood collection in neonates with royalties paid to Promotec Medizintechnik, and a patent Tub for surfactant treatment in neonates issued and is working as head of a department of pediatrics. Evangelisches Waldkrankenhaus Spandau and its employee FJ have received support for scientific and educational activities by companies that market nutritional products. None of the support has influenced the writing or conclusions of the manuscript. FJ’s contribution to the study was financed by board resources supported by the Ev. Waldkrankenhaus Spandau, which is a non-profit hospital. JF reports personal fees from Humana GmbH. All authors have read and approved the final manuscript. *Corresponding author: Tel.: +49 30 3702 1037; Fax: +49 30 3702 2380. E-mail address: [email protected] (H. Petersen). https://doi.org/10.1016/j.nut.2020.110728 0899-9007/© 2020 Elsevier Inc. All rights reserved.

Introduction Early childhood nutrition can have long-term health effects. For these so-called programming effects, the first 1000 d after conception are considered a particularly vulnerable period [1]. Breast milk is regarded as the gold standard for early childhood nutrition. However, exclusive breastfeeding cannot be achieved at all times. Therefore, further research related to the ideal composition of infant formula is warranted. To ensure adequate supply with all essential and semi-essential amino acids, conventional cow’s milk
based formulas have so far contained significantly higher total protein concentrations than breast milk. As a result, formula-fed infants receive a significantly higher total protein intake in the first months of life than exclusively breast-fed infants [2]. Higher protein intake in bottle-fed infants seems to contribute to higher increase in body weight observed in formula-fed infants. According to the so-called “earlyprotein hypothesis,” an increased protein intake via early childhood nutrition promotes insulin and insulin-like growth factor

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H. Petersen et al. / Nutrition 74 (2020) 110728

(IGF)-1 secretion, resulting in faster weight gain and increased fat deposition [3]. Rapid first-year growth may lead to a predisposition for adult obesity [4
6]. The ideal amount of protein in infant formulas is still being debated [7]. At present, protein content in infant formulas is set at a range between 1.8 and 3.0 g/100 kcal [8
10]. According to recommendations from medical societies and European regulatory bodies, formulas with a protein content of <2 g/100 kcal should be subject to nutritional validation [8,11]. Enrichment with bovine a-lactalbumin provides sufficient quantities of essential amino acids in the context of a reduced total protein concentration. This prospective randomized, double-blind, controlled trial aimed to demonstrate that an a-lactalbumin
enriched infant formula, with a protein content of 1.89 g protein/100 kcal, is suitable and safe for the exclusive nutrition of infants in the first months of life and supports adequate growth. Methods Study design In a randomized, double-blind controlled trial, healthy newborn infants were assigned to receive either a low- or high-protein content formula (1.89 versus 2.1 g/100 kcal). A breast-fed reference group was studied concurrently. The study € was submitted to the ethics committee (Ethik-Kommission der Arztekammer Berlin), where ethical approval was obtained and was registered with Clinical Trials. After parental informed consent and upon enrollment, formula-fed study participants were randomly assigned to receive one of the study formulas. Randomization was done using a computer-generated randomization list with a permuted block size of four, after sex stratification. Two letters each were used to label the low- and high-protein content formula. Study staff and parents of study participants were blinded for coding and formula type. Letter codes were only disclosed to the statistician performing final analysis. The study protocol was left unchanged after commencement of trial. Participants Infants where recruited from the maternity ward of our institution. Only mothers who had decided to stop breastfeeding were approached for enrollment in the formula groups. In the breast-fed reference group, infants had to be predominantly breast-fed (maximum 20% of additional formula feeding). Included were healthy, full-term infants (gestational age 37/0 to 41/6 wk), with a birthweight adequate for gestational age (>3 and <97 percentile according to Voigt et al. [12]), aged
30 d of life. Infants with a family history of atopic disease or diagnosed with congenital, chromosomal, or metabolic disorders influencing growth were excluded from study participation. Study feedings Composition of study formulas complied with the 2006 EU Directive on Infant Formulae and Follow-on Formulae [13]. Study formulas were manufactured and provided to the families free of charge during the first 6 mo by Humana, DMK Baby GmbH (Bremen, Germany). Study formula was fed on demand from the time of enrollment to 6 mo of age. The primary intervention period was 3 mo after study enrollment. A change of formula of up to 10 meals per month was tolerated, without making study exclusion mandatory. Premature introduction of complementary foods during the intervention period led to study exclusion. Compositional differences of the isocaloric formulas consisted in protein (1.89 versus 2.1 g/100 kcal), carbohydrates (12.3 versus 12.1 g/100 kcal), and protein composition (whey-to-casein ratio 40:60 versus 58:40, a-lactalbumin amount of 1.67 g/ 100 g versus 1.23 g/100 g in the final formula; main components are listed in Table 1). The source of the a-lactalbumin was an a-lactalbumin
enriched whey protein isolate (a-lactalbumin content = 53.49 g / 100 g raw material). The experimental lowprotein formula contained skim milk and the a-lactalbumin-enriched whey protein isolate, whereas the commercial high-protein formula contained skim milk, demineralized whey powder, and 0.14 g added amino acids per 100 g of finished powder formula Amino acid compositions of the formulas are listed in Table 2). Procedures Growth parameters Birth weight and length were recorded from patient records. All other anthropometric measurements (weight, length, and head circumference) and skinfold thickness were performed by four trained medical investigators, using standard procedures. Anthropometric measurements were recorded at study enrollment,

Table 1 Composition of the study formulas

Energy Lipids Carbohydrates Protein Whey Casein Whey:Casein a-lactalbumin a-lactalbumin

Unit

Low-protein formula

High-protein formula

kcal/100 mL g/100 kcal g/100 kcal g/100 kcal g/100 g g/100 g g/100 g

65 4.8 12.3 1.89 9.33 3.72 5.61 40:60 1.67 18

65 4.8 12.1 2.1 10.54* 6.16 4.24 58:40* 1.23 12

in g/100 g in % of total protein

*Amino acids added.

after 6 (data not shown) and 12 wk of study participation, and at follow-up. Baseline anthropometric measurements were obtained at randomization. Measurement of body weight was carried out on a calibrated electronic scale (seca 336, Hamburg, Germany) measured to the nearest 1 g. Recumbent length was recorded to the nearest 1 mm by means of a measuring rod with a fixed head part and movable foot part (seca 232 measuring rod). Head circumference was measured to the nearest 1 mm using non-stretch measuring tape (seca 212 measuring tape). Weight gain was calculated as the difference of body weight from the assessment at 12 wk to the weight at study inclusion, divided by the time interval in days. Growth velocity and increase in head circumference were calculated, respectively. Measurement of skinfold thickness was performed using a caliper (Harpenden Skinfold Caliper, HaB International, Warwickshire, UK) at two body sites (supscapular and triceps) on the right-hand side of the body. Fat percentage was determined using the Slaughter formula [14] via an online calculator [15] using a weight rounded to the nearest 10 g. To improve comparability with other studies, outcomes were expressed as SD scores (Z-scores) using the calculator provided by the World Health Organization (WHO Anthro version 3.2.2). Formula consumption and caloric intake Parents of formula-fed infants were asked to record daily quantities of milk consumption for a 3-d period before the corresponding study visit. The average of each 3-d protocol was taken to calculate average daily fluid intake and caloric intake per kilogram current body weight recorded at the correspondent study visit. Food-related complaints All parents were asked to record any food-related complaints in the daily frequency of their occurrence as part of the 3-d documentation. Food-related complaints were defined as colic (crying episodes of >30 min duration without any other recognizable cause), heavily distended abdomen, and flatulence, as well as posseting after the meal. Statistical analysis The primary endpoint was the average weight gain in g/d during the 12-wk intervention period. Sample size was calculated to detect a growth difference of 3 g/d. Assuming a standard deviation of §4.5 g/d, inclusion of 28 infants per formula group was necessary (one-sided testing, a-level 0.05, power 0.8). Estimating a dropout rate of 30%, this number was enhanced to a target of 40 infants in each group. Statistical analysis was carried out by a statistical investigator independent of the study group with the NCSS statistical system [16]. Data are provided as mean § SD. For statistical comparison of normally distributed continuous data of the three study groups, parametric one- or two-way analysis of variance (ANOVA) were used. Four tests were applied before the application of parametric one-way ANOVAs to assess the assumptions required for parametric one-way ANOVA: Skewness Normality of Residuals, Kurtosis Normality of Residuals, Omnibus Normality of Residuals, and modified Levene Equal Variance Test. Otherwise Kruskal
Wallis non-parametric ANOVAs were used. The difference between the two formula groups was assessed by two-sample t test or its non-parametric counterpart (i.e., Wilcoxon rank sum test depending on the tests of assumption for applicability of t test). The assumptions were tested by the following tests of normality in each group: Skewness-, Kurtosis, and Omnibus Normality. For the equivalence of variances, two tests were used: Variance Ratio Equal Variance Test and Modified Levene Equal Variance Test. Analysis of dropout was done using x2 test or Fisher’s exact test. Analysis was only performed in per protocol cases because infants who changed type of feeding after randomization were excluded from further follow-up according to study protocol.

H. Petersen et al. / Nutrition 74 (2020) 110728

Results Eighty infants were randomized to receive one of the study formulas: 41 in the low-protein group and 39 in the high-protein group. The non-randomized reference group consisted of 40 breast-fed infants. Fifty-two infants in the formula group (low protein: 26, high protein: 26) and 32 in the breast-fed reference group completed the 3-mo intervention period. Of the study participants in the formula group, 35% (low protein: 37%, high protein: 33%) did not complete the intervention period. In the breast-fed reference group, 20% did not complete the intervention period. Attrition during the intervention period in the

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formula-fed group was mainly due to change of formula type (low protein: 8, high protein: 9), or due to loss to follow-up (low protein: 7, high protein: 4). Breast-fed infants mainly dropped out owing to discontinuation of breastfeeding/insufficient milk production (n = 5) and lost to follow-up (n = 3). When all participants had completed their first year of life, follow-up data for 31 infants in the formula-fed group (low protein: 16 of 41, high protein: 15 of 39) and 30 infants in the breast-fed reference group were obtained (for flow diagram of participants see Fig. 1). Randomization was successful, and baseline characteristics of both formula groups showed a similar distribution (Table 3).

Fig. 1. Flowchart of randomization and follow-up of study participants in all three feeding groups.

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feeding groups. Mean length gain during the intervention period was identical (1.2 mm/d) in all three feeding groups. Increase in head circumference was assessed using parametric one-way ANOVA and showed no significant difference during the intervention period. Mean daily increase in head circumference was 0.6 mm in all three feeding groups. One-way ANOVA was applied to assess Z-scores of anthropometric parameters and body composition. No significant difference was found between the study groups in Z-scores for weight, length, head circumference, weight-for-length, and body mass index (BMI) nor for fat percentage at end of intervention (3 mo), and after 6 and 12 mo of follow-up. (Table 5 provides anthropometric measurements).

Table 2 Amino acid compositions of the formulas compared with reference Amino acid

Unit

Low-protein formula

High-protein formula

Reference*

28 49 96 188 164 42 86 86 33 85 107

30 49 114 202 163 46 86 111 34 87 123

38 40 90 166 113 23 83 77 32 76 88

mg/100 kcal Cysteine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Tyrosine Valine

Safety parameters

*Reference values from EFSA [9].

Average weight gain

Mean formula consumption was 161 and 143 mL/kg body weight in the low-protein group and 156 and 138 mL/kg body weight in the high-protein group at 6 and 12 wk, respectively. There was no statistically significant difference in the formula uptake between the two groups using two-sample t test (Wilcoxon rank sum test). Mean caloric intake in the low-protein group was 104 and 93 kcal/kg body weight and 101 and 90 kcal/kg body weight in the high-protein group at 6 and 12 wk, respectively. There was no statistically significant difference in mean caloric intake between the two groups using two-sample t test (Wilcoxon rank sum test).

Regarding the primary endpoint of weight gain at the end of the intervention period (12 wk), no statistically significant difference was found among the feeding groups using parametric one-way ANOVA. Mean weight gain was 32, 31, and 33 g/d in the low-protein group, high-protein group, and breast-fed reference group, respectively (Table 4). Mean weight gain in boys was significantly higher than in girls in all feeding groups. Mean weight gain in the low-protein formula group was 36 and 27 g/d, in the high-protein group 32 and 30 g/d, and in the breast-fed reference group 36 and 31 g/d for boys and girls, respectively.

Food tolerance Regarding food-related complaints (colic, flatulence, or posseting), no statistically significant difference was found among the three feeding groups at 6 and 12 wk using Kruskal
Wallis nonparametric one-way ANOVA.

Other anthropometric measurements Differences in length gain were assessed using the Kruskal
Wallis one-way ANOVA. There was no significant difference among the

Table 3 Baseline characteristics of study participants by feeding group Interventional group Low-protein group

Birth weight (Z-score) Length (Z-score) Head circumference (Z-score) Weight-for-length (Z-score) BMI (Z-score) Fat percentage

Observational group

High-protein group

Human milk

n

Mean § SD

n

Mean § SD

n

Mean § SD

P-value*

26 26 26 26 26 26

0.17 § 0.75 0.7 § 0.95 0.64 § 0.75
0.58 § 1.26
0.33 § 1.02 8.7 § 1.7

26 26 26 26 26 26

0.20 § 0.54 0.97 § 1.00 0.88 § 0.81
0.82 § 1.17
0.43 § 0.80 8.8 § 1.9

32 32 32 32 32 32

0.20 § 0.77 0.77 § 0.91 0.78 § 1.10
0.55 § 1.00
0.42 § 1.17 8.6 § 1.5

0.98 0.58 0.64 0.64 0.93 0.96

ANOVA, analysis of variance; BMI, body mass index. *Parametric one-way ANOVA.

Table 4 Average weight gain (g/d), growth, and increase in head circumference by feeding group Interventional group Low-protein group

Weight gain (g/d) 12 wk Growth (mm/d) 12 wk Increase head circumference (mm/d) 12 wk

Observational group

High-protein group

Human milk

n

Mean § SD

n

Mean § SD

n

Mean § SD

P-value

26 26 26

32 § 7 1.2 § 0.3 0.6 § 0.2

26 26 26

31 § 7 1.2 § 0.2 0.6 § 0.1

32 32 32

33 § 7 1.2 § 0.2 0.6 § 0.1

0.66* 0.96y 0.25*

ANOVA, analysis of variance. *Parametric one-way ANOVA for the three feeding groups. y Kruskal
Wallis one-way ANOVA.

H. Petersen et al. / Nutrition 74 (2020) 110728

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Table 5 Anthropometric measurements by feeding group at 3, 6, and 12 mo Interventional group Low-protein group n Weight (g) (Z-score)

3 mo

26

6 mo

22

6 mo

3 mo

26

22

12 mo

25

3 mo 6 mo 12 mo 3 mo

16

26 22 16 26

26 25 15 26

16.11 § 1.25
0.41 § 0.83 6 mo

22

(kg/m2) (Z-score) 12 mo

3 mo 6 mo 12 mo

26 22 16

32 31

26 25 15

68.19 § 3.45 0.52 § 1.46


0.91

74.25 § 2.70
0.36 § 0.92


0.49

40.17 § 1.33 0.26 § 1.02


0.99

43.34 § 1.43 0.34 § 0.96


0.99

45.80 § 1.42 0.23 § 0.93
0.26 § 1.18 0.09 § 0.92 0.27 § 0.99


0.45 0.35 0.20 0.15

16.20 § 1.63
0.3 § 1.11


0.63

17.08 § 1.42
0.05 § 0.96


0.20

17.07 § 1.4 0.34 § 0.97 16.9 § 2.7 17.93 § 2.9 16.28 § 3.9


0.16 0.37 0.39 0.87

31 16.62 § 1.76
0.40 § 1.17

15 17.58 § 1.19 0.63 § 0.81 15.9 § 3.1 16.9 § 2 16.75 § 3.2


0.84

32

25

16

61.24 § 2.06 0.46 § 0.94

30 46.22 § 1.44 0.48 § 1.20
0.69 § 1.17
0.30 § 1.18 0.36 § 1.17 15.76 § 1.59
0.56 § 1.13

17.36 § 1.29 0.12 § 0.87


0.26

31 43.35 § 1.25 0.38 § 0.98

15 46.88 § 1.14 0.82 § 0.91
0.49 § 0.92 0.20 § 0.85 0.66 § 0.83

9432 § 1174 0.04 § 0.98

32 40.17 § 1.11 0.24 § 0.94

43.62 § 1.20 0.36 § 0.92


0.53

30 75.21 § 2.73
0.08 § 0.97

40.35 § 1.20 0.23 § 0.98 6 mo

(kg/m2) (Z-score) Fat percentage

15

26

7965 § 1028 0.24 § 1.01

31 68.40 § 2.01 0.65 § 1.03

76.47 § 2.76 0.35 § 1.09

(cm) (Z-score)

BMI (kg/m2) (Z-score)

25

16


0.84

32 61.57 § 2.24 0.62 § 1.22

68.84 § 1.57 0.52 § 1.11 12 mo

(cm) (Z-score) Weight-for-length (Z-score)

26

22

(cm) (Z-score)

6081 § 744 0.04 § 0.97

30 9712 § 1261 0.23 § 1.06

61.67 § 1.69 0.49 § 0.82

P value*

31 7790 § 1024 0.06 § 1.11

15

26

Mean § SD

32

25

16

Human milk n

5985 § 761
0.10 § 1.05

10291 § 1025 0.65 § 0.89 3 mo

Mean § SD

26

8230 § 707 0.39 § 0.83 12 mo

(cm) (Z-score) Head circumference (cm) (Z-score)

High-protein group n

6124 § 547
0.03 § 0.64

(g) (Z-score) (g) (Z-score) Length (cm) (Z-score)

Mean § SD

Observational group

30 17.15 § 1.71 0.37 § 1.18 16.1 § 2.9 17.03 § 3.9 16.05 § 4.3

32 30 30

ANOVA, analysis of variance; BMI, body mass index. *Parametric one-way ANOVA.

Discussion The present study demonstrated that a modified infant formula, with a reduced protein content of 1.89 g protein/100 kcal and enrichment with a-lactalbumin, was suitable and safe for the exclusive nutrition of infants in the first months of life. No significant difference in growth was found among feeding groups during the intervention period or the follow-up period of 1 y. Study formula was fed on demand and in terms of safety we demonstrated that there was no significant difference in formula and caloric uptake between the two formula groups. No relevant adverse events were reported in either of the feeding groups and parental report did not indicate any untoward effects. Results from the present study, indicating the safety of lowprotein formula in healthy full-term infants, are compatible with previous studies. In a systematic review including four trials with 1399 healthy full-term infants, Abrams et al. concluded that lowprotein formula leads to adequate growth during infancy and early childhood [17].

Although most studies demonstrate similar growth between infants in the low-protein group and breast-fed infants, some studies show a significant effect on growth. It could be shown that by reducing the protein concentration in formula, slower weight gain, similar to breast-fed children, could be induced [18
20]. As discussed by Abrams et al., previously mentioned trials were characterized by larger differences in protein content between study groups and higher number of study participants in addition to longer intervention and follow-up periods [17]. CHOP (European Childhood Obesity Trial) was a randomized, double-blind controlled trial with 1138 healthy full-term infants [6,18,19]. During an intervention period of 12 mo, infants were fed two stages of isocaloric formulas with a considerable difference in protein concentration (~65
100% higher protein content in the high-protein formula, compared with the low-protein formula). At the ages of 1, 2 and 6 y, children in the high-protein group showed higher Z-scores for BMI and an increased risk for obesity [6,7,18]. Consistent with the present results, other studies did not demonstrate a significant effect on growth in the first 12 mo of life

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[21
23]. These studies were of small sample size and had shorter intervention and follow-up periods and lower differences in protein content (~5
45%) between study groups [17]. In the present study, the distinction between the high- and low-protein groups was rather scant, with a mere ~14% difference in protein concentration between the two protein concentrations. In combination with a short intervention period, this could explain similar growth in all study groups. However, despite the duration of the intervention period being defined as 3 mo, because during this time period formula was the near exclusive nutrient source, formulas were provided free of charge for the duration of 6 mo and were continuously fed in the intervention groups. Because there was no significant difference in formula volume and caloric uptake between the two formula groups, the lack of difference in growth was unlikely due to increased formula volume intake in the low-protein group. Fomon et al. studied the nutritional adequacy of a formula with a protein-energy ratio of 1.7 g/100 kcal [24]. In their study, infants fed a low-protein formula demonstrated adequate growth. However, in feeding on demand, an increased formula intake (and thus higher caloric intake) was registered in the low-protein group. This was interpreted as a possible compensatory mechanism to an inadequate intake, thereby questioning safety of this formula. In addition to protein quantity, protein quality is an important aspect that needs to be considered to ensure a sufficient intake of essential amino acids. A-lactalbumin is rich in essential amino acids [12] and is the major protein in breast milk (20
25% of total protein) [25]. In the present study, the low-protein formula was enriched by a-lactalbumin. Previous trials have demonstrated safety and age-appropriate growth in infants fed formula enriched with a-lactalbumin and a lower protein concentration [26,27]. In one trial, an increased energy efficiency was observed in infants fed an a-lactalbumin
enriched formula, supposedly due to an improvement in the formula protein composition [27]. This could explain the unexpected tendency for higher means in body weight in the low- compared with the high-protein group in the present study. One strength of our trial is the low risk of selection bias owing to randomization and a low risk for performance bias owing to double blinding for the intervention group. Outcome assessors were blinded, thereby minimizing detection bias. On the other hand, the present study results are subject to several limitations, the most important of which is the high dropout rate. Attrition was higher than initially estimated. Switching of formula is a widespread phenomenon in the local population whenever parents discern a potential issue, such as prolonged crying or interrupted sleep. There was, however, no significant difference of attrition between the low- and high-protein formula groups, nor between any of the three study groups, indicating no difference in tolerance. Owing to limited sample size (caused by high attrition), the present study might be underpowered to detect any minor influence on growth. However, when comparing all feeding groups, not even a tendency of a diverging growth performance could be detected. To avoid false incentives against breastfeeding, there was no financial support for study participants in the intervention group other than provision of formula free of charge, whereas families of breast-fed infants received transport compensation. Conclusion The present study demonstrated that an a-lactalbumin
enriched infant formula, with a protein content of 1.89 g protein/100 kcal, is

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