Infant Feeding Practices and Their Association with Early-Life Nutrient Intake: Baseline Findings from the Baby-Act Trial

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This great article attempts to evaluate energy intake in the context of infant feeding. The tables are well informative. I have some remarks:

Results: although breastfeeding appears to deliver less energy, this does not need to be a disadvantage, as it also provides for several immune factors, not present in artificial formulas.

Statistics: you are using the ANCOVA, but would the MANOVA not be a more accurate alternative?

Author Response

Comment 1

Results: although breastfeeding appears to deliver less energy, this does not need to be a disadvantage, as it also provides for several immune factors, not present in artificial formulas.

RESPONSE: please see revisions to clarify that this is not a disadvantage but the other way around. 

 

Comment 2

Statistics: you are using the ANCOVA, but would the MANOVA not be a more accurate alternative?

RESPONSE: as suggested, we changed the analyses to MANCOVA. Please see updated results. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Congratulations on taking on an important topic from the public health perspective. The following comments are intended to strengthen the article:

Introduction: In this section, I suggest adding a little more information about the influence of different macronutrient intakes (especially protein) on the growth and weight of infants and young children - it is worth familiarizing the reader with basic information about metabolic programming.

Materials and methods: I suggest adding a graphical representation of the study design - this makes it much easier for the reader to familiarize with the study.

The authors mention the division into children receiving complementary food and those not receiving it. According to the recommendations, infants aged 0-2 months should not receive such food. Can the authors clarify what they meant by complementary food: solid meals or maybe fluids other than breast milk or milk formula? In the case of infant formula feeding, was data collected on a specific product? In such a case, could the nutritional value of the formula declared by the manufacturer be used? The authors used a single value for milk/formula consumption for all infants. In the case of newborns, this value may be lower in practice. This should be taken into account in the study limitations.

Results: Table 1: What does Technical/associate education mean? Is it at the high school level or is it vocational education? To make the level of education more understandable to a wider group of readers, also outside the US, it might be worth indicating the years of education?

Table 4: Table 4: I wonder why the values ​​for infants fed exclusively breast milk were different for boys and girls? If for each infant regardless of sex the amount of milk was the same - 780.7 ml? Please explain.

Table 4: The large differences in energy and macronutrient intake between breastfed and formula-fed and mixed-fed infants are very intriguing (472 kcal vs. 622 vs. 712 kcal/day). Did the authors observe differences in the infants' body weight? How can the authors explain this?

Discussion: The discussion lacked some reference to nutrtional standards and recommendations - the authors indicated lower energy and macronutrient intake by breastfed infants and higher in the rest. So did breastfed infants receive a sufficient amount of diet/nutrients compared to nutritional standards? Or maybe their intake was below the recommended values? Or did formula-fed infants receive more energy and nutrients compared to recommendations?

Author Response

Comment 1

Introduction: In this section, I suggest adding a little more information about the influence of different macronutrient intakes (especially protein) on the growth and weight of infants and young children - it is worth familiarizing the reader with basic information about metabolic programming.

RESPONSE: Thanks for your comment. The following was added at the end of the 1st paragraph in the introduction:

"For many years, studies have attributed these differences in growth trajectory to differences in protein intake among infants fed formula [9, 10], but more recent studies have not found that a higher protein intake is associated with greater weight gain or higher weight velocity among healthy infants [11, 12]."

 

Comment 2

Materials and methods: I suggest adding a graphical representation of the study design - this makes it much easier for the reader to familiarize with the study.

RESPONSE: Thanks for your comment. Since this was a cross-sectional analysis of the baseline visit of the Baby-Act trial, we considered that providing the reference for the protocol would be sufficient . In future publications on the effects of the intervention on diet or weight gain, we will definitively consider adding a graphical representation of the study design. 

 

Comment 3

The authors mention the division into children receiving complementary food and those not receiving it. According to the recommendations, infants aged 0-2 months should not receive such food. Can the authors clarify what they meant by complementary food: solid meals or maybe fluids other than breast milk or milk formula? In the case of infant formula feeding, was data collected on a specific product? In such a case, could the nutritional value of the formula declared by the manufacturer be used? The authors used a single value for milk/formula consumption for all infants. In the case of newborns, this value may be lower in practice. This should be taken into account in the study limitations.

RESPONSE: Thanks for your comment. Yes, we meant by complementary food the consumption of foods other than milk. Although the recommendation is clear that infants this age should only consume milk, some caregivers (n=10) were already introducing those foods. We clarified this in the methods section. The FFQ did not ask about the brand of the infant formula but we added in methods more information of how this was calculated: 

"This database was created for all the foods included in the FFQ based on foods typically consumed by infants in this age group [17]. For the infant formula, this database averaged the energy and nutrient values from the 10 most consumed infant formulas available in NDSR."

Nevertheless, we added in limitations the following: "For infant formula, we did not collect specific brands but used an average nutritional value for several formulas included in the NDSR".

 

Comment 4

Results: Table 1: What does Technical/associate education mean? Is it at the high school level or is it vocational education? To make the level of education more understandable to a wider group of readers, also outside the US, it might be worth indicating the years of education?

RESPONSE: this was added as suggested. 

 

Comment 5

Table 4:  I wonder why the values ​​for infants fed exclusively breast milk were different for boys and girls? If for each infant regardless of sex the amount of milk was the same - 780.7 ml? Please explain.

RESPONSE: We apologize, this was a mistake. We used breast milk data per month from a recent meta-analysis. Although most infants were 0-2 months, there were a few that were 3 or 4 months, which explains the variability (see table 1 for mean and sd age for infants). The corrected version was added in the revised manuscript as:

"For breastmilk volume intake, this was first calculated using the data from a recent meta-analysis of 167 studies conducted by Rios-Leyvraz and Yao [19] with breastmilk data for infants for each month from 0 to 24 months. The volume reported in the Rios-Leyvraz and Yao [19] was used as the breastmilk volume by the age in months, if infants were exclusively breastfed. If infants were partially breastfed, the volume in formula was subtracted from the volume as per that study [19] and what remained was considered as breastmilk volume intake. If the daily volume of formula exceeded the estimated total daily milk intake volume, a rule of 3 ounces (88.7 ml) per feeding was implemented, which was derived from the Feeding Infants and Toddlers Study (FITS) 2008 and 2016, the largest US cross-sectional surveys of caregivers of children from 0-48 months of age [20]".

 

Comment 6

Table 4: The large differences in energy and macronutrient intake between breastfed and formula-fed and mixed-fed infants are very intriguing (472 kcal vs. 622 vs. 712 kcal/day). Did the authors observe differences in the infants' body weight? How can the authors explain this?

RESPONSE: we did review body weight differences by feeding type but because these were very young infants, the body weight at this age is very much influenced by pregnancy. We are completing the data collection for the visit at 12 months to be able to conduct a longitudinal analysis of diet and weight changes at 12 months. 

 

Comment 7

Discussion: The discussion lacked some reference to nutrtional standards and recommendations - the authors indicated lower energy and macronutrient intake by breastfed infants and higher in the rest. So did breastfed infants receive a sufficient amount of diet/nutrients compared to nutritional standards? Or maybe their intake was below the recommended values? Or did formula-fed infants receive more energy and nutrients compared to recommendations?

RESPONSE: thanks for your comment. Based on your comment, we calculated the estimated energy requirements per infant as per the Dietary Reference Intake and all infants met this. This was added in methods, results, and discussion.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Thank to the Authors for responding the comments