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DASH (2016)

Citation:

Asemi Z, Samimi M, Tabassi Z, Sabihi SS, Esmaillzadeh A. A randomized controlled clinical trial investigating the effect of DASH diet n insulin resistance, inflammation, and oxidative stress in gestational diabetes. 2013, Nutrition, 29: 619-624.

PubMed ID: 23466048
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To investigate the effects of the DASH diet on insulin resistance, serum high-sensitivity C-reactive protein and biomarkers of oxidative stress among pregnant women with gestations diabetes Mellitus (GDM).
Inclusion Criteria:
  • Pregnant women aged 18 to 40 years, diagnosed with GDM at 24 to 28 weeks' gestation
  • Pregnant women without a previous diagnosis of glucose intolerance, no previous history of GDM, non-smokers, having GDM based on previously mentioned criteria.
Exclusion Criteria:
  • Premature pre-term rupture of membrane
  • Placenta abruption
  • Pre-eclampsia
  • Those who needed to commence insulin therapy or were on insulin therapy
  • Recommendation of complete bed rest
  • Hypothyroidism, kidney or liver disease
  • Women taking estrogen therapy.
Description of Study Protocol:
  • Recruitment: The women were recruited in the clinics affiliated with Kashan University of Medical Sciences (Iran) from April to December 2011
  • Design: Randomized, two-arm, parallel clinical trial
  • Blinding used: All the study personnel and participants were blinded to dietary assignment, but the dietitian who provided dietary education. Randomization was done using a computer-generated random numbers.
Intervention
  • DASH diet
    • ?Rich in fruits, vegetables, whole grains, low-fat dairy products, low in saturated fats, cholesterol, refined grains and sweets
    • Composition: CHO, 40% to 55%; PRO, 10% to 20%; fat, 25% to 30%
    • Sodium intake was less than 2,000mg per day.
  • Control diet: Same macronutrient composition.
  • Participants were choosing the foods from a prescribed list. The compliance of diet monitored weekly through phone interviews and double-checked by the use of three-day dietary records completed throughout the study.
Statistical Analysis
Non-normality distributed variables used log transformation
Student's T-test and paired-samples T-test were used to analyze the data
P<0.05 was considered statistically significant.
Data Collection Summary:

Timing of Measurements
All anthropometric and biochemical assessments were measured at baseline and after four weeks of intervention.

Dependent Variables

  • Fasting plasma glucose (FPG)
  • Serum insulin
  • Serum high-sensitivity C-reactive protein (HS-CRP)
  • Homeostasis of assessment-insulin resistance (HOMA-IR)
  • Plasma antioxidant capacity (TAC)
  • Total glutathione levels (GSH).

Independent Variables

  • DASH diet
  • Control diet.
Description of Actual Data Sample:
Initial N

38.

Attrition (Final N)

  • 32 (16 in DASH; 16 in control)
  • Lost to follow-up
    • Pre-eclampsia: Four
    • Bed rest: One
    • Insulin therapy: One.
Age
  • Control: Mean, 29.7±5.6 years
  • DASH: Mean, 27.7±5.4 years.

Ethnicity

N/A.

Other Relevant Demographics

GTT at baseline was the same between groups except the first hour, when the DASH Group had a higher GTT than Control (203.87mg vs. 190.73mg per dL; P<0.05), respectively.

Anthropometrics

Pre-pregnant weight, baseline and final weight, pre-pregnancy, baseline and final BMI were not different between the two groups.

Location

Kashan, Iran.

Summary of Results:

Key Findings

Variables DASH Diet Group Control Group Statistical Significance of Group Difference
Mean changes from Weeks 0 to 4 Mean Changes from Weeks 0 to 4
FPG (mg/dL)

-7.62±2.64

3.68±4.17

P=0.02
Insulin (mcIU/ml) -2.62±1.92 4.32±2.37 P=0.03
HOMA-IR -0.8±0.43 1.1±0.71 P=0.03
TAC (mmol/L)

45.2±16.49

-159.24±39.73

P<0.0001
GSH (mcmol/L)

108.17±40.51

-150.96±48.55

P<0.0001

FPG, fasting plasma glucose
GSH, total glutathione
HOMA-IR, Homeostasis model of assessment - insulin resistance
TAC, total antioxidant capacity.

Other Findings

  • DASH Diet Group showed a significant increase in the TAC and GSH levels after four weeks, but the Control Group had a significant decrease (P=0.001)
  • Dietary diet results showed an increase in total carbohydrate and fructose intake, but a decrease in simple sucrose consumption with the DASH diet, compared to the control diet; 392±7g vs. 318±42g per day (P<0.0001); 13.4±1.2g vs. 9±1.8g per day (P=0.001); 9.1±0.9g vs. 19.8±1.2g per day (P<0.0001).
Author Conclusion:
  • Consumption of the DASH diet in pregnant women with GDM had beneficial effects on FPG, serum insulin levels, HOMA-IR score, plasma TAC and total GSH levels
  • The effects of this dietary pattern on pregnancy outcomes need to be investigated in future studies.
Funding Source:
University/Hospital:
Reviewer Comments:
  • Interpretation of the results may be jeopardized due to the limitations of the statistical analysis as well as the lack of diet adherence
  • Small sample size increases risk for type 2 error
  • The study also was limited by its short duration
  • Limited generalizability due to population studied.
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? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? No
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.) No
  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? No
  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? Yes
  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? 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? 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? 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? 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? 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? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? No
  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? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
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