EAL

DASH (2016)

Citation:

Asemi Z, Samimi M, Tabassi Z, Esmaillzadeh A. The effect of DASH diet on pregnancy outcomes in gestational diabetes: A randomized controlled clinical trial. Eur J Clin Nutr. 2014; 68: 490-495. PubMed ID: 24424076

Study Design:

Randomized Controlled Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

To investigate the effects of the DASH eating plan on pregnancy outcomes in pregnant women with gestational diabetes mellitus (GDM).

Inclusion Criteria:

Primigravida pregnant women
Age 18 to 40 years
Diagnosed with GDM by a 100g oral glucose tolerance test at 24 to 28 weeks of gestation.

Exclusion Criteria:

A previous glucose intolerance or GDM diagnosis
Premature pre-term rupture of the membrane
Placenta abruption
Pre-eclampsia
To commence insulin therapy during the intervention
Complete bed rest
Hypothyroidism
Urinary tract infection
Smoking and kidney or liver diseases
Taking estrogen therapy.

Description of Study Protocol:

Recruitment

Pregnant women attending maternity clinics affiliated to Kashan University of Medical Sciences were screened for GDM.

Design

In this two-arm parallel randomized controlled trial subjects were randomly assigned to consume a control diet or DASH diet for four weeks after stratification for pre-intervention body mass index (BMI less than 30kg/m² and 30kg/m² or more) and weeks of gestation (less than 26 or 26 weeks or more). The control diet contained 45% to 55% CHO, 15% to 20% protein and 25% to 30% total fat. The calorie content and protein content of the DASH diet was similar to the control but was rich in fruits, vegetables, whole grains and low-fat dairy products, and low in saturated fats, CHO, refined grains and sweets with a sodium intake of 2,400mg per day. The authors did not specify how subjects were instructed on the assigned diet. Subjects were not to alter routine physical activity or receive any lipid-lowering or anti-hyperglycemic medications during the intervention. Diet consumption was monitored through once-weekly phone interviews and three one-day food records (two week days and one weekend day) throughout the four-week intervention. Maternal anthropometric measures were taken at baseline and at four weeks by trained midwives; fasting blood samples were also taken at baseline. All subjects were followed until delivery; they were called once a week post-intervention to ask if they had started insulin injections. Mode of delivery was recorded, as well as length, weight, head circumference, Apgar score and ponderal index of the infant.

Intervention

Subjects were randomly assigned to consume diets with similar kcal and protein amount, but were either:

DASH diet rich in fruits, vegetables, whole grains and low-fat dairy products, and low in saturated fat, cholesterol, refined grains and sweets with 2,400mg per day of sodium
Control diet made up of 45% to 55% carbohydrate, 15% to 20% protein and 25% to 30% total fat.

Statistical Analysis

The following tests were used:

Histogram tests
Kolmogorov-Smirnov tests
Student's T-test
X² test
Analysis of covariance.

Data Collection Summary:

Timing of Measurements

Body weight and height were measured by trained midwives at baseline and after four weeks of intervention, and BMI was calculated. Fasting blood samples were taken at baseline to evaluate plasma glucose levels.

Dependent Variables

Delivery mode (Cesarean section or vaginal)
Need for insulin therapy after intervention
Gestational age (weeks)
Macrosomia (birth weight higher than 4,000g)
Polyhydramnios
Newborn head circumference (cm)
Ponderal index (kg/m³)
Apgar score.

Independent Variables

Subjects were randomly assigned to consume either:

Control diet
DASH diet.

Control Variables

Subjects consumed diets with similar kcal and protein contents. Subjects were asked not to change routine physical activity or to receive any anti-hyperglycemic or lipid-lowering medications.

Description of Actual Data Sample:

Initial N: N=58 pregnant women
Attrition (final N): N=52 pregnant women.

Age

Control diet: 30.7±6.3 years
DASH diet: 31.9±6.1 years.

Ethnicity

Iranian.

Other Relevant Demographics

Gestational age before intervention:

Control diet: 25.9±1.4 weeks
DASH diet: 25.8±1.4 weeks
P=0.77.

Anthropometrics

Subjects were evenly matched on:

Height (cm): 160.4±6.4 (control diet), 159.8±3.6 (DASH diet) (P=0.67)
Pre-pregnancy weight (kg): 73.8±11.3 (control diet), 68.8±10.9 (DASH diet) (P=0.11)
Weight at end of trial (kg): 81.3±12.3 (control diet), 75.9±11 (DASH diet) (P=0.1)
BMI at study baseline (kg/m²): 31±4.9 (control diet), 29.2±3.5 (DASH diet) (P=0.12)
BMI at end of trial (kg/m²): 31.7±5 (control diet), 29.7±3.6 (DASH diet) (P=0.11)
Fasting plasma glucose at baseline (mg per dL): 95.3±12.6 (control diet), 96.4±15 (DASH diet) (P=0.76).

Location

Kashan, Iran.

Summary of Results:

Key Findings

No significant difference was seen in kcal intake; however, significant differences were found in saturated fat, polyunsaturated fat, cholesterol, dietary fiber, simple sugar, sodium, potassium, magnesium, calcium and vitamin C between the two groups (P<0.05 for all)
A total of 46.2% of the DASH diet group needed a Cesarean section vs. 80.8% for the control diet group (P=0.01)
A total of 23% of the DASH diet group required insulin after intervention vs. 73% for the control diet group (P<0.0001)
A total of 3.8% of the DASH diet group had macrosomic infants compared with 38.5% of the control diet group (P= 0.002)
Infants of mothers in the DASH diet group has significantly lower weight (3,222.7 vs. 3,818.8, P<0.0001), head circumference (34.2cm vs. 35.1cm, P=0.01), and ponderal index (2.50 vs. 2.87, P<0.0001) compared with those born to mothers in the control diet group
The DASH diet on pregnancy outcomes remained significant even after controlling for pre-pregnancy BMI, baseline maternal fasting plasma glucose and maternal age.

Author Conclusion:

Consumption of a DASH eating pattern for four weeks among pregnant women with GDM resulted in a decreased rate of cesarean section, reduced need to commence insulin therapy after intervention and lower rates of macrosomic babies. Mean weight, head circumference and ponderal index of infants born to mothers in the DASH diet group were significantly lower compared with those born to mothers in the control diet.

Funding Source:

University/Hospital:

KUMS, Kashan, Iran

Reviewer Comments:

The study authors did not describe how subjects were educated or instructed on the assigned eating plan (DASH or control). The authors do state other limitations, including:

Short duration of the study
Compliance to the DASH diet with a biomarker was not assessed
Effect of the DASH diet on other pregnancy outcomes including neonatal glucose levels, respiratory distress syndrome and hyperbilirubinemia were not assessed.

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?	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%.)	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?		No
	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.)	No
	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?	???
	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?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	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?	N/A
	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