GDM: Fat (2016)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To compare the effects of a MUFA-rich diet with the recommended high-carbohydrate diet on 24 hour ambulatory blood pressure, glycemic control, blood lipids, and insulin sensitivity in women with GDM.

Inclusion Criteria:
  • Women screened for gestational diabetes (GDM) before the 34th gestational week : history of obesity, diabetes mellitus in relatives, previous  GDM, birthweight >4500g, stillbirth, age above 38y or current glucosuria.

 

Exclusion Criteria:
  • Exclusion criteria were any hypoglycemic, anti-lipidemic or antihypertensive medication
Description of Study Protocol:

Recruitment

Women were recruited over a two year period from a clinic in Denmark.

Design

Randomization blocked (sizes 6 and 2) and stratified by prepregnancy weight (obese vs normal weight). 

Blinding used (if applicable)

None specified.

Intervention (if applicable)

After diagnosis with GDM, women were instructed to follow a high-carbohydrate diet until the 34th gestational week.  After randomization, they were treated with normo- and isocaloric diets containing either high carbohydrate (H-CHO) or high monounsaturated fatty acids (H-MUFA) during the last 7 weeks of the pregnancy.

Statistical Analysis

  • Two-way ANOVA and regression with post-hoc testing using Newman-Keuls' test
  • Non-normal data were log-transformed
  • Significance assessed by unpaired t-test or Mann-Whitney test
  • Sample size calculation : 80% power to detect 0.65 mmol/l difference in mean cholesterol with n=10 in each group
Data Collection Summary:

Timing of Measurements

33rd, 36th, 38th gestational week: clinical and 24 h ambulatory blood pressure and IVGTT

Dependent Variables

  • Insulin response and glucose via IVGTT - performed with infusion of 50% glucose solution over 1 min.  Blood samples taken at time 0, 2, 3, 4, 5, 6, 8, 10, 14, 19, 30, 40, 60, 90, 120, 180 min to measure insulin and glucose.
  • Blood pressure - portable automatic monitor by oscillometry.  The average of three oscillometric and ausculatory measurements was taken. 
  • Urinary albumin, glucose, sodium, potassium and creatinine measured via 24 h urine sample along with 24hr blood pressure measurement
  • Lipids measured with Enichom Chem 1 analyser; glucose by glucose oxidase method; serum insulin by radioimmunoassay; HbA1c by commercial kit

Independent Variables

  • High carbohydrate (H-CHO) or high monounsaturated fatty acids (H-MUFA) during the last 7 weeks of the pregnancy
  • Diet assessed by weighed food records for 3 days at study entry and gestational week 37. Coded by a dietitian using Dankost, 1980

Control Variables

  • Body mass index
Description of Actual Data Sample:

Initial N: 36 women had a positive oral glucose tolerance test.  27 enrolled.

Attrition (final N): 27.  1 missing IVGTT; 2 missed week 36 visit; two women missed week 38

Age: Mean (SD) : 31(1) H-MUFA, 29 (1) H-CHO

Ethnicity: not stated - study conducted in Denmark

Other relevant demographics: week 33 BMI 35.3 (2.4) in H-MUFA and 32.2 (1.5) in H-CHO

Anthropometrics no baseline differences mentioned by the authors

Location: hospital in Denmark

 

Summary of Results:

 Insulin Sensitivity outcomes:

Variables

H-MUFA

Mean change, Wk 38-33, ±SD

H-CHO

Mean change, Wk 38-33, ±SD

Statistical Significance of Group Difference

Fasting glucose, mmol/l (n=26)

-0.5 ± 0.3

-0.4±0.18

0.77

Fasting insulin, mU/l (n=26)

-2.9 ± 4.5

 

 -6.8 ± 1.7

 0.43

Insulin sensitivity,10^-5 min^-1 per mU/l min (n=26)

-0.28± 0.16 0.08± 0.05 0.04

 

Variables

H-MUFA

Mean change, Wk 38-33, ±SD

H-CHO

Mean change, Wk 38-33, ±SD

Statistical Significance of Group Difference

Fasting glucose, mmol/l (n=26)

-0.5 ± 0.3

-0.4±0.18

0.77

Fasting insulin, mU/l (n=26)

-2.9 ± 4.5

 

 -6.8 ± 1.7

0.43

Insulin sensitivity,10^-5 min^-1 per mU/l min (n=26)

-0.28± 0.16 0.08± 0.05 0.04

 Blood pressure outcomes

Variables

H-MUFA

Mean Wk 38, ±SD

H-CHO

Mean Wk 38 , ±SD

Statistical Significance of Group Difference

Ambulatory Systolic, mmHg

 123± 6

122±5

not reported

Ambulatory Diastolic, mmHg

81± 4

 

 80 ± 3

not reported

24-hr Systolic, mmHg

126± 5 128± 5 <0.04

24-hr Diastolic, mmHg

75± 3 

 80± 3 

<0.04

Week 37 Diet Measures

Variables

H-MUFA

Mean Wk 37 ± SD

H-CHO

Mean Wk 37 ± SD

Statistical Significance of Group Difference

Energy, kcal

 1982± not reported

1727 ± not reported

not reported

Protein, % kcal

16± 1

 

 80 ± 3

not reported

Carbohydrate, % kcal

46± 1 50± 1 0.01

Total Fat, % kcal

37± 1 

 30± 2 

 0.001

  Saturated fat, % kcal 10± 1 13± 1 not reported
  Monounsaturated, %kcal 22± 1 11± 1 0.001

Other Findings

 

 

Author Conclusion:

In pregnancy complicated by GDM, a high-MUFA diet may prevent the expected rise in blood pressure without exerting adverse effects on lipid and lipoprotein concentrations.  This was not mediated via changes in insulin sensitivty.  The H-CHO diet had a possible advantage over MUFA-enriched diet in amerliorating the decline of insulin sensitivity in third term of pregnancy.

Funding Source:
University/Hospital: Skejby Hospital, Aarhus University, Odense University, Diabetes
Reviewer Comments:

Study sample not well described.

Few details regarding intervention (i.e. how were women instructed, by whom, how long)

Sample size calculated based on changes in lipids but intervention duration of 5 weeks is less than the 6 weeks needed to detect lipid changes.

 

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) 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? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? ???
  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? ???
  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%.) 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? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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? 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? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? No
  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? No
  6.6. Were extra or unplanned treatments described? No
  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? 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? No
  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)? Yes
  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? 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