EAL

BF: Dietary Factors, Breast Milk and Infant Outcomes (2008)

Citation:

Dusdieker LB, Hemingway DL, Stumbo PJ. Is milk production impaired by dieting during lactation? AJCN. 1994; 59: 833-840.

PubMed ID: 8147327

Study Design:

Before-After Study

Class:

D - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

Over a 10-week period of maternal energy restriction and weight loss, to determine 1) whether milk production and infant weight gains continues normally; and 2) whether the protein and fat contents of milk are adversely affected.

Inclusion Criteria:

Well-nourished (BMI>19) women, breastfeeding on demand, without chronic illness
Infants 30d to 100d old
Singleton pregnancies
Infants appropriate for- or large-for-gestational age at term and without chronic illness or major congenital anomalies
Infants consuming only breast milk and growing well (height and weight more than fifth percentile).

Exclusion Criteria:

Infant
- Failed to gain weight for two consecutive weeks without intercurrent illness
- Failed to gain weight at rate equal to or more than fifth percentile for age
- Received more than 120ml supplementary formula a day.
Mother
- Milk supply at end of each two-week segment was markedly less than preceding period
- Failed to lose 0.45kg per week (averaged every two weeks).

Description of Study Protocol:

Recruitment

Recruited from Pediatric Continuity Care Clinic, University of Iowa Hospitals and Clinics

Design

10-week cohort study

Intervention

10-week energy restriction of 25% less than predicted energy requirements (decreased fat intake, excessive E-intake)

Statistical Analysis

Descriptive statistics; paired and unpaired T-tests.

Data Collection Summary:

Timing of Measurements

Baseline (five days)

Mothers and infants weighed and measured
Skinfold thicknesses measured
Mother's waist and hip circumferences measured
Mothers instructed on diet recording and given scale to complete weighed food records for five days
Mothers to quantify five-day milk production via test weighing at home
Mothers' preliminary theoretical energy (E) needs calculated (E requirement both including and excluding lactation) and compared with five-day baseline weighed food records.

Energy restriction (10 weeks)

25% less than predicted E needs via decreasing fat intake and identifying and modifying eating behaviors contributing to excess energy intake
Target weight loss of 0.45kg per week
Personalized behavior therapy with dietitian
Three low-fat, portion-controlled frozen meals provided weekly
Weights of moms and infants measured weekly
Mothers recorded weekly two-day record
Every two weeks, repeated infant test-weighings to quantify milk production.

At four, eight and 10 weeks

Breast milk obtained for analysis via complete emptying of one breast using hand expression or hand pump
Women instructed to shake this sample well and collect 30ml aliquot to be analyzed.

At week 10

Repeat skinfold thickness, hip and waist measurements.

Post-study

Four-week phase for those who were dismissed before 10-week study ended
Resumed non-dieting E allowance, breastfeeding
Infants test-weighed weekly, two-day diet record reviewed weekly.

Dependent Variables

Milk volume
Milk composition
Infant growth.

Independent Variables

E restriction for 10 weeks.

Control Variables

Timing of measurements
Weighed food records
Infant test-weighings
Weight-loss goal.

Description of Actual Data Sample:

Initial N: 33

Attrition (final N): 22

Age: 32.1y±4.1y

Ethnicity: Not reported

Other relevant demographics:

Anthropometrics - Baseline Characteristics

Average gestational weight gain of women completing study was 14.5kg; women exceeded their pre-pregnancy weight at baseline by 5.18kg.

	N=22, Completers
	mean±SD
Weight, kg	68.6±9.6
Height, cm	165.0±6.0
Sum skinfold thicknesses, mm	79.4±18.2
E-intake, kcal/d	2,300±592
Milk production, ml/d	759±142
Infant age, d	56.2±25.6
Infant weight, kg	5.3±0.77
Birth weight, kg	3.54±0.28

Location: Department of Pediatrics and Clinical Research Center, University Iowa, Iowa City, IA, USA

Summary of Results:

33 mother-infant pairs enrolled in the study, and 22 women completed the 10-week study. The 11 women who dropped out before study completion were the same age, height and weight and had similar skinfold thicknesses as women who completed the study. Women who dropped out consumed significantly less energy than those women who completed the study. Compared with those women who remained in the study, those who dropped out had similar milk production, and their infants were the same age and had similar birth weights as well as similar weights at the start of the study.

For the 22 women completing the 10-week study:

Variables	Baseline (mean±SD)	End of 10-week Diet Phase (mean±SD)	Statistical Significance
Weight, kg	68.4±9.4	63.6±9.1	P=0.0001
Energy intake, kcal/d	2,303±602	1,765±419	P=0.0001
Sum of three skinfold thicknesses, mm	79.2±18.7	63.2±17.9	P=0.0001
Hip circumference, cm	104.7±7.2	100.3±6.8	P=0.0001
Waist circumference, cm	81.2±5.7	75.1±4.8	P=0.0001
Milk production, ml/d	759±142	802±189	P<0.05
N of milk, g/l	1.82±0.32	1.62±0.27	NS
Fat of milk, %	4.06±2.15	4.00±2.56	NS

For infants, weight-for-age percentiles at weeks zero and 10 did not differ for male infants; for female infants 83.7±12.0 at Baseline to 73.0±17.9 kg (P<0.05). Infants' sum of skinfolds was significantly greater at 10 weeks vs zero weeks (P=0.03).

Author Conclusion:

Well-nourished, healthy lactating women can safely lose 0.45kg per week while supplying adequate milk (quantity and quality) to maintain infant growth. To ensure safety, mother's diet and infant growth should be monitored and evaluated every one to two weeks by a registered dietitian or primary care physician.

Funding Source:

Reviewer Comments:

11 of 33 women did not complete the 10-week study. Four dropped out before the third week of the diet phase. Seven completed three or more weeks. Main reason for drop-out was inability or unwillingness to comply with study procedures (e.g., test-weighings); other reasons included difficulty with dietary compliance and using supplementary formula due to returning to workplace.

Limitation: Analyses were only done for the 22 women who completed the study.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	???

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	Yes
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	Yes
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		???
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	Yes
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	No
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	No
	8.6.	Was clinical significance as well as statistical significance reported?	???
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	Yes
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes