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


Lauritzen L, Hope C, Straarup EM, Michaelsen KF. Maternal fish oil supplementation in lactation and growth during the first 2.5 years of life. 2005; Pediatr Res. 58 (2): 235-242.

PubMed ID: 16006428
Study Design:
Randomized controlled trial
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Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To study the effect of maternal fish oil consumption during zero to four months of lactation on growth in infant and early childhood development.

Inclusion Criteria:

Pregnant women in their eighth month of gestation; fish intake below the median (less than 0.40g/d n-3 long chain polyunsaturated fatty acid -LCPUFA) and fish intake in the upper quartile (greater than 0.82g/d n-3 LCPUFA); uncomplicated pregnancy, BMI less than 30kg/m2, no metabolic disorders and intention to breastfeeding for at least four months. Healthy newborns (no admission to neonatal department); term; singleton infants with normal weight for gestation and an Apgar score less than seven to five minutes after delivery. 

Exclusion Criteria:
  • None except not meeting all inclusion criteria
  • Excluded from analysis: All drop-outs are reported in another article from the same authors using the same population.
Description of Study Protocol:


From April 1999 to 2000 pregnant women with eight month of pregnancy, all from the Copenhagen area, were recruited from the Danish National Birth Cohort (DNBC).


The diet of the pregnant women was determined in the 25th week of gestation by a food frequency questionnaire. After birth, the women with a fish intake less than the 50th percentile were randomly allocated to supplementation with fish or olive oil in blocks of two in five strata according to mean parental education. Women with a high fish intake (less than 0.82g/d n-3 LCPUFA) were the reference group for the study. The fish oil group received an equivalent amount of n-3 LCPUFA which is the habitual intake of the women in the DNBC population with the highest fish intake (greater than the 90th percentile). Supplements were given in as müsli bars or homemade cookies or as capsules in a daily basis for the first four months of lactation. The lower amount of oil supplied by the capsules was taken into account in the calculation of overall supplement compliance. Supplements were taken within two weeks after birth. Infants who took part in the study were either exclusively breastfeeding or not during the first four months. Most of the infants who were breast-fed during this period were from the fish oil group. Degree of breastfeeding was taking into account in the analysis. The newborns were followed-up for nine months and when they completed 2.5 years old, all families were invited to participate in the follow-up. The dietary intake of the 2.5 years old children was assessed for seven consecutive days using a pre-coded dietary questionnaire.

Blinding used

Investigators and families were blinded to the randomization throughout the first year of life of the infants.


Müsli bar and homemade cookies (microencapsulated oils):

  • Fish oil group: 4.5 grams per day (1.5g n-3 LCPUFA: 0.62g EPA and 0.79g DHA
  • Olive oil group: 4.5 grams per day of olive oil.


  • Fish oil group: 4.0 grams per day (1.4g of n-3 LCPUFA: 0.36 EPA and 0.99g DHA)
  • Olive oil group: 4.0 grams per day of olive oil.

Statistical Analysis

T-test or ANOVA combined with Bonferroni post-hoc tests were used for comparisons between groups for all normally distributed continuous variables. Nominal variables were compared by X2 analysis, and variables in the ordinal scales and those without normal distribution were compared by a Mann-Whitney U test. Multiple regression analysis of observed differences in the head circumference and body composition were measured at  2.5 years of age using a general linear model. The same model was used when energy intake was added to analyze body composition at the same age. All multiple models were checked for absence of heroscedasticity because the groups presented homogeneous variances. When evaluating the possible associations between anthropometric measures and biochemical effect of the intervention Pearson analysis of univariate correlation was used, as well a multiple general linear model with inclusion of these variables plus the degree of breastfeeding.


Data Collection Summary:

Timing of Measurements

Blood was collected at the end of four month-intervention period to measure the red blood cells (RBC) fatty acids from the mothers. Anthropometric measures and body composition were measured in children at birth, two, four and nine months and at two and one-half years old.

Dependent Variables

  • Maternal RBC-DHA
  • Total saturated fat 
  • Total monounsaturated fat
  • Total n-6 PUFA
  • Total n-3 PUFA
  • Head circumference
  • Weight
  • Length or height
  • BMI
  • Waist circumference
  • Triceps and sub-scapular skin fold
  • Percent body fat
  • Lean body mass.

Independent Variables

Fish oil: n-3 LCPUFA vs. olive oil

 Control Variables

  • Age
  • Energy intake
  • Estimated energy intake from breast milk during intervention.


Description of Actual Data Sample:

Initial N

175  women  (122 intervention trial; 53 reference group)

Attrition (final N)

150 women (100 intervention trial; 50 reference group); 101 children at 2.5 years old (72 intervention trial; 58 reference group).

Family drop-out after four-month intervention and children at 2.5 years of age at follow-up: 11 were lost at follow-up, six had moved far away from the area, 15 did not wish to attend the follow-up examination for various personal reasons and 13 did not give any reason for the lack of participation. Four children were uncooperative during the examination.


Mean age (mother): 30.56±4.1


Not mentioned

Other relevant demographics

A total of 107 mothers complied with the criterion for exclusive breastfeeding for four months. However, mothers, who did not fulfill this criterion were not excluded from the trial or analysis. Breast milk covered more than 90% of the intake for 16 non-exclusively breast-fed infants, 75-90% for nine of the infants, 50-75% for three infants and less than 50% for 15 infants. The degree of breastfeeding during the four months intervention and the maternal n-3 LCPUFA intake during lactation were the same for all three groups.


Age, mean parental education, maternal pre-pregnancy BMI, paternal height, numbers of siblings, sex ratio in group and weeks of gestation were well-matched for all three groups in the beginning of the study. However, maternal height was higher among pregnant women in the high fish intake group compared to those in the fish oil group. The weight, height and head circumference of infants at birth did not differ from those who participated and those who did not, however there was a slight over-representation of boys in the follow-up group.


Copenhagen, Denmark


Summary of Results:

Fatty acid composition of maternal red blood cells before and after the intervention trial period

The DHA content of RBC fatty acid was significantly increased after intervention period in the fish oil group; from 7.7±1.1% in the beginning of the trial to 8.8±1.2% at the end of intervention period. However, in the olive oil group the concentration of DHA in the RBC after the intervention period was significantly decreased when compared to the beginning of the trial; 5.5±1.1% and 7.7±1.03% respectively. The fish oil supplement increased significantly the DHA content of RBC fatty acid compared to the olive oil supplement; P<0.00.

  • Growth in weight, length, and head circumference did not differ between the randomized groups up to nine months
  • Growth and body composition of children at two and one-half years old.
Variables Hig Fish Group Fish Oil Group (FO) Olive Oil Group (OO) Non-adjusted Mean Difference (P-value) Adjusted Mean Difference (P-value)
Head circumference (cm) 50.62±1.29 50.42±1.23*  49.74±1.34    
Height (cm) 93.74±2.93 92.58±3.14  92.65±3.04     
Weight (Kg) 14.18±1.43 14.16±1.26  13.71±1.26     
BMI 16.11±1.08  16.51±1.08*  15.86±1.21  0.65±0.28(0.022) 0.80±0.28(0.006)
Waist circumference (cm) 49.5±3.0  50.2±2.4 48.6±2.7 1.54±0.63(0.017 1.80±0.65(0.007)
Triceps skin fold thickness (mm) 9.3±2.2  9.7±1.8 8.9±1.7  0.79±0.44(0.076 1.14±0.44(0.012)
Number Sub-scapular skin fold (mm) 6.4, 4.1-8.7  6.5, 4.7-10.0 6.1, 4.7-7.8  (0.147) 1.06-1.21(0.020)
Sum of skin fold (mm) 15.7±3.6 16.5±3.3  15.0±2.6  1.47±0.76(0.057) 2.15±0.77(0.007)
Percent body fat 15.1±3.2 15.9±2.9   14.5±2.5 1.35±0.69(0.055) 1.65±0.69(0.021)
Lean body mass (kg) 12.0±1.0 11.9±1.1  11.7±1.0  0.15±0.25(0.553)       --

*The value of the FO-group is significantly different from that of the OO group (P<0.05); and differences in body composition between the two randomized groups (FO and OO) controlled for sex, ponderal index at birth and current energy intake; number median, 10th to 90th percentile.

  • The differences in body composition between the two randomized groups became evident when the comparisons were controlled for sex, ponderal index at birth and current energy intake
  • The difference in BMI remained when expressed as z scores, being 0.1±0.9 in the fish oil vs. -0.5±1.0 in the olive oil group; P<0.013. 

Other findings

  • BMI, waist circumference, and percentage of body fat at 2.5 years old were positively associated with the DHA content of maternal RBCs at the end of the intervention period (r=0.238, P=0.021; r=0.301, P=0.007; and r=0.264, P=0.035, respectively). BMI and waist circumference were also positively associated with the DHA content in a sample of breast milk at four months.
  • All associations between BMI, waist circumference, TST; percentage of body fat and maternal RBC-DHA were significantly after control for sex, ponderal index at birth, current energy intake, and degree of breastfeeding; P=0.003, 0.002, 0.001 and 0.002 respectively.
  • In the randomized groups, head circumference at 2.5 years of age was positively associated with maternal RBC-DHA at the end of the intervention period (r=0.257, P=0.017). When these parameters were controlled for sex, head circumference at two months, and the degree of breastfeeding during the intervention period, the association was no longer significant. These parameters explained 63% of the variation in head circumference (P<0.001), with head circumference at two months being the most significant of the included determining factors.


Author Conclusion:

The n-3 LCPUFA intake of lactating mothers may be important for growth of young children. The long-term effect on weight and BMI remains to be investigated.

Funding Source:
Government: The Danish Research and Development Program for Food and Technology
Reviewer Comments:

The sample population is the same used in the study published before (2004). The drop-outs during the intervention period are not mentioned in this study. Methodology about the supplement amounts is very confusing. The supplements differed in composition when taken as capsule; DHA concentration is higher in the capsule supplement. The number of children in the fish oil group was higher than in the olive oil group.

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? 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? Yes
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) Yes
  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? 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? 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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  4.4. Were reasons for withdrawals similar across groups? ???
  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? Yes
  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.) Yes
  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? 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? N/A
  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? N/A
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)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  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? ???
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? No