GDM: Fat (2016)
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.
-
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 were any hypoglycemic, anti-lipidemic or antihypertensive medication
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
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
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
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
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.
University/Hospital: | Skejby Hospital, Aarhus University, Odense University, Diabetes |
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
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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 | |