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


Okamura T, Takeuchi T, Nishi O, Yaginuma T, Kawana T.  Effects of low-caloric diet in puerperium on prolactin, TSH, estradiol and milk secretion.  Acta Obst Gynaec Jpn. 1987; 39(11): 2059-2055.


PubMed ID: 3123579
Study Design:
Randomized controlled trial
A - Click here for explanation of classification scheme.
Quality Rating:
Negative NEGATIVE: See Quality Criteria Checklist below.
Research Purpose:

To determine how a three-day low-calorie diet during puerperium (early postpartum period) affects prolactin and breastfeeding. 

Inclusion Criteria:

Not reported.

Exclusion Criteria:

Not reported.

Description of Study Protocol:

Recruitment: Not reported.

Design: Short-term (six-day) randomized trial.

Blinding used: Not reported.


Random assignment to one of two groups:

1)  Low-caloric (LC): 1,200kcal per day for three days followed by "ordinary" 1,800kcal per day for three days

2)  Ordinary-caloric (OC): 1,800kcal per day for six days.

Statistical Analysis: No analysis plan reported.


Data Collection Summary:

Timing of Measurements

Study began immediately after birth. Subjects randomly assigned to one of two diet groups; controlled diets for six days. 

For the first three days, women ate breakfast and had blood samples drawn. Women milked both breasts for one minute each via electric breast pump from day zero to day five postpartum; then they fed infants.

N=4 women in LC and OC groups; underwent thyrotropin-releasing hormone stimulation test on days one and three.


Dependent Variables

  • Prolactin
  • Milk composition (CHO, pro, fat)
  • Milk output: Both breasts were milked for one minute each via electric breast pump from day one to five postpartum; how total milk output measured is not clear (whether this was measured by infant test-weighing or the two one-minute pumpings)
  • TSH
  • Cortisol.

Independent Variables

Random assignment to one of two diets:


  Six-Day Ordinary (OC), N=15

Three-Day Low (LC), followed by Three-Day OC, N=10

kcal/day 1,800-1,900 1,200
Protein (g/day) 70-80 62
Fat (g/day) 55-60 39
CHO (g/day) 250 155

Control Variables

Timing of measurements.

Description of Actual Data Sample:


Initial N: N=25.

Attrition (final N): N=10 in LC, 15 in OC.

Age: Not reported.

Ethnicity: Not reported

Other relevant demographics: None reported.

Anthropometrics: None reported.

Location: Dept OB-GYN, University of Tokyo at Mejirodai, Tokyo, Japan.


Summary of Results:

Milk output gradually increased from day zero to six, although overall volume in LC was less than volume in OC (NS). On day one, LC volume (0.4±1.1ml) was significantly less than OC volume (4.5±3.7ml, P<0.01). 

No significant differences in milk composition on day four through six; no analysis on day zero through two due to low volume for analysis. LC group milk tended to contain less fat and protein than OC milk (NS). 

Prolactin levels in LC except at day zero tended to be less than OC; significant difference only at day one (P<0.05).  Serum TSH in LC tended to be less than OC during six days (NS).  No significant differences in estradiol or cortisol between groups. 


Author Conclusion:

Although there was little difference in milk composition between low- and ordinary-caloric diets, after three days of consuming a low-calorie diet (1,200kcal per day), prolactin, TSH and milk secretion were suppressed.  As such, a low-calorie diet may not be advisable for breastfeeding women during the early postpartum period. 

Funding Source:
Reviewer Comments:

Study conducted during the first week postpartum. 

Study population consisted of Japanese women, whose energy needs may be different from other groups of women due to their shorter stature, bone density, etc.

Basic demographic and reproductive variables not described for the two groups. 

How energy intake was controlled, determined and measured for the six days was not reported; feeding schedules for mothers and infants not reported; there was a range of intakes for women in the OC group vs. very specific intakes of carbohydrate, protein and fat for the LC group.

How energy intake determined appropriate for women was not determined; maternal body weight not reported to determine if intake of calories, carbohydrate, protein and fat was adequate. It may not have been the energy-intake deficit affecting hormone levels, but low protein intake. 

Very low milk volume (outputs). 

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) ???
  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) Yes
Validity Questions
1. Was the research question clearly stated? No
  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? No
2. Was the selection of study subjects/patients free from bias? No
  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? No
  2.2. Were criteria applied equally to all study groups? ???
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? ???
  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? N/A
  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? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  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? ???
  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.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  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? No
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? No
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  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? ???
  6.8. In diagnostic study, were details of test administration and replication sufficient? No
7. Were outcomes clearly defined and the measurements valid and reliable? ???
  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? ???
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  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? No
  8.1. Were statistical analyses adequately described and the results reported appropriately? No
  8.2. Were correct statistical tests used and assumptions of test not violated? ???
  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)? ???
  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? N/A
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