Elsevier

Nutrition

Volume 29, Issue 4, April 2013, Pages 619-624
Nutrition

Applied nutritional investigation
A randomized controlled clinical trial investigating the effect of DASH diet on insulin resistance, inflammation, and oxidative stress in gestational diabetes

https://doi.org/10.1016/j.nut.2012.11.020Get rights and content

Abstract

Objective

To our knowledge, no reports are available indicating the effects of the Dietary Approaches to Stop Hypertension (DASH) eating plan on insulin resistance, inflammation, and oxidative stress among pregnant women with gestational diabetes mellitus (GDM).

This study was designed to investigate the effects of the DASH diet on insulin resistance, serum high-sensitivity C-reactive protein (hs-CRP) and biomarkers of oxidative stress among pregnant women with GDM.

Methods

This randomized controlled clinical trial was performed with 32 pregnant women diagnosed with GDM at 24 to 28 wk gestation. Participants were randomly assigned to consume either the control (n = 16) or DASH diet (n = 16) for 4 wk. The DASH diet was rich in fruits, vegetables, whole grains, and low-fat dairy products and was low in saturated fats, total fats, cholesterol, refined grains, and sweets, with a total of 2400 mg/d of sodium. The control diet contained 40% to 55% of its energy as carbohydrates, 10% to 20% as proteins, and 25% to 30% as total fats. Fasting blood samples were taken at baseline and after 4 wk of intervention to measure fasting plasma glucose (FPG), serum insulin, and hs-CRP, Homeostasis Model of Assessment—Insulin Resistance (HOMA-IR), plasma total antioxidant capacity (TAC), and total glutathione levels (GSH).

Results

Consumption of the DASH diet compared with the control diet resulted in decreased FPG (–7.62 versus 3.68 mg/dL; P = 0.02), serum insulin levels (–2.62 versus 4.32 μIU/mL, P = 0.03), and HOMA-IR score (–0.8 versus 1.1; P = 0.03). Increased concentrations of plasma TAC (45.2 versus –159.2 mmol/L; P < 0.0001) and GSH (108.1 versus –150.9 μmol/L; P < 0.0001) also were seen in the DASH group compared with control group. We failed to find a significant difference in mean changes of serum hs-CRP levels between the two diets. Within-group comparisons revealed significant reductions in plasma TAC and GSH levels in the control diet, while a significant increase in these biomarkers in the DASH diet.

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.

Introduction

Gestational diabetes mellitus (GDM) is a condition in which pregnant women without previously diagnosed diabetes exhibit high blood glucose levels especially during the third trimester [1]. It affects 3% to 6% of all pregnancies, depending on the studied population [2]. The precise mechanisms underlying GDM remain unknown. The main hallmark of GDM is increased insulin resistance [3]. Increased production of placental hormones, especially cortisol, progesterone, human chorionic somatomammotropin (HCS), and to a lesser extent increased fat deposits during pregnancy result in insulin resistance during pregnancy [3], [4]. Elevated circulating levels of inflammatory markers, particularly highly sensitive C-reactive protein (hs-CRP) and tumor necrosis factor (TNF)-α, in GDM can predict the progression to type 2 diabetes (T2D) later in life [5], [6], [7]. Some studies also have shown that enhanced lipid peroxidation and oxidative stress results in the development of GDM [8], [9]. Gestational diabetes has been associated with increased risk for developing fetal macrosomia, prematurity, birth trauma, fetal death, and respiratory distress syndrome in offsprings, as well as maternal morbidity [10], [11], [12], [13], [14]. Pregnant women with GDM are at an increased risk for developing T2D later in life [15].

Various strategies, including diet therapy [16], [17], the use of oral hypoglycemic agents [18], and insulin injections [19], have been suggested for management of GDM. The use of antioxidants, vitamins E and A, have resulted in a lower circulating level of inflammatory factors and biomarkers of oxidative stress during pregnancy [20], [21], [22]. The Dietary Approaches to Stop Hypertension (DASH) eating plan was originally suggested for patients with hypertension [23]; however, its effects on cardiovascular risk factors [24], features of metabolic syndrome [25], and metabolic profile of diabetic patients [26] have recently been shown. Azadbakht et al. [26] have demonstrated that consumption of the DASH diet for 8 wk was associated with decreased serum levels of hs-CRP in patients with diabetes. These investigators also reported the beneficial effects of this dietary pattern on CRP, coagulation abnormalities, and hepatic function tests [26]. Improvements in insulin sensitivity and lipid profiles also have been documented with adherence to the DASH diet along with exercise and weight loss in hypertensive overweight patients [27].

The DASH diet is a low-glycemic index, low energy-dense diet that contains higher amounts of dietary fiber, phytoestrogens, potassium, magnesium, folic acid, and other beneficial nutrients [24], [25]. To the best of our knowledge, no reports are available indicating the effects of the DASH diet on insulin resistance, inflammation, and biomarkers of oxidative stress in pregnant women with GDM. The aim of the current study, therefore, was to investigate the effects of the DASH eating plan on insulin resistance, serum hs-CRP, and biomarkers of oxidative stress on pregnant women with GDM.

Section snippets

Participants

This randomized, two-arm, parallel clinical trial was carried out in Kashan, Iran, from April 2011 to December 2011. On the basis of the sample size formula suggested for randomized clinical trials [26] and considering the type I error of 5% (α = 0.05), type II error of 20% (β = 0.2; Power = 80%), and serum hs-CRP level as a key variable, we reached the sample size of 16 women for each group. Pregnant women ages 18 to 40 y diagnosed with GDM by a 100-g oral glucose tolerance test at 24 to 28 wk

Results

Mean age, pre-pregnancy weight, and BMI were not statistically different between the two groups (Table 1). Baseline weight and BMI as well as postintervention means for these variables were not significantly different between the DASH and control groups.

Based on 3-d dietary records, no statistically significant difference was seen between the two groups in terms of energy and protein intake; however, significant differences were observed in dietary intakes of carbohydrates, fats, saturated

Discussion

We found that consumption of the DASH eating pattern in pregnant women with GDM had beneficial effects on FPG, serum insulin levels, HOMA-IR score, and biomarkers of oxidative stress. Total energy intake of participants in the control and the DASH groups was the same; however, the energy density of the DASH diet was lower than the control diet. To our knowledge, this study is the first reporting the effects of the DASH diet on insulin resistance and biomarkers of oxidative stress in GDM.

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.

Acknowledgment

The present study was supported by a grant (No. 91104) from the vice-chancellor for research, KUMS, and Iran. The authors would like to thank the staff of Naghavi and Shaheed Beheshti Clinics (Kashan, Iran) for their assistance in this project. The study was supported by a grant (no. 91104) from Kashan University of Medical Sciences.

Clinical trial registration number: IRCT201204065623N2.

Name of trial registry: Effects of the Dietary Approaches to Stop Hypertension (DASH) on metabolic profiles

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      Nutritional interventions in patients with different forms of pregnancy complication and different outcome measures have been examined. One of these investigations is the Dietary Approaches to Stop Hypertension (DASH) (Asemi et al., 2013, 2014). This diet was originally designed to normalize blood pressure in patients with hypertension.

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    ZA and AE contributed in conception, design, statistical analysis, and drafting of the manuscript. ZT, MS, and SS contributed in data collection and manuscript drafting. AE supervised the study. AE is the guarantor who takes full responsibility for the work as a whole, including the study design, access to data, and the decision to submit and publish the manuscript. None of the authors had any personal or financial conflict of interest. All authors approved the final version for submission Clinical trial registration number: IRCT201204065623N2.

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