A Randomized Controlled Trial Investigating the Effects of a Low-Glycemic Index Diet on Pregnancy Outcomes in Gestational Diabetes Mellitus

Jimmy Chun Yu Louie, MNUTRDIET, APD; Tania P. Markovic, MBBS, PHD; Nimalie Perera, MBBS; Deborah Foote, BSC DIPNUTRDIET, APD; Peter Petocz, PHD; Glynis P. Ross, MBBS; Jennie C. Brand-Miller, PHD

Disclosures

Diabetes Care. 2011;34(11):2341-2346. 

In This Article

Abstract and Introduction

Abstract

OBJECTIVE The prevalence of gestational diabetes mellitus (GDM) is rising. There is little evidence to demonstrate the effectiveness of one dietary therapy over another. We aimed to investigate the effect of a low–glycemic index (LGI) versus a conventional high-fiber diet on pregnancy outcomes, neonatal anthropometry, and maternal metabolic profile in GDM.
RESEARCH DESIGN AND METHODS Ninety-nine women (age 26–42 years; mean ± SD prepregnancy BMI 24 ± 5 kg/m2) diagnosed with GDM at 20–32 weeks' gestation were randomized to follow either an LGI (n = 50; target glycemic index [GI] ~50) or a high-fiber moderate-GI diet (HF) (n = 49; target GI ~60). Dietary intake was assessed by 3-day food records. Pregnancy outcomes were collected from medical records.
RESULTS The LGI group achieved a modestly lower GI than the HF group (mean ± SEM 47 ± 1 vs. 53 ± 1; P < 0.001). At birth, there was no significant difference in birth weight (LGI 3.3 ± 0.1 kg vs. HF 3.3 ± 0.1 kg; P = 0.619), birth weight centile (LGI 52.5 ± 4.3 vs. HF 52.2 ± 4.0; P = 0.969), prevalence of macrosomia (LGI 2.1% vs. HF 6.7%; P = 0.157), insulin treatment (LGI 53% vs. HF 65%; P = 0.251), or adverse pregnancy outcomes.
CONCLUSIONS In intensively monitored women with GDM, an LGI diet and a conventional HF diet produce similar pregnancy outcomes.

Introduction

Gestational diabetes mellitus (GDM) is commonly defined as any degree of glucose intolerance with onset or first recognition during pregnancy.[1] In developed nations, between 4 and 8% of pregnant women are presently affected,[2–4] and the prevalence will rise dramatically if the guidelines of the new International Association of Diabetes in Pregnancy Study Groups (IADPSG) are adopted.[3] The main adverse outcome of GDM is excessive fetal growth resulting in higher risk of large-for-gestational-age (LGA) infants (birth weight >90th centile). Higher birth weight has been linked with childhood obesity,[5] cardiovascular disease,[6] and diabetes[5] later in life.

In the medical management of GDM, the primary goal is to maintain maternal blood glucose concentrations, especially postprandial levels, within an acceptable range.[7] Interventions that reduce postprandial glucose levels, including dietary strategies such as carbohydrate restriction, have been shown to be effective in reducing LGA and later obesity in type 1 diabetic offspring.[8]

Postprandial glycemia can be reduced without carbohydrate restriction by slowing down the rate of carbohydrate digestion and absorption. Compared with moderate–or high–glycemic index (GI) foods containing similar amount of carbohydrates, low-GI (LGI) foods have been demonstrated to reduce postprandial glucose in healthy individuals.[9] The GI of various foods has been shown to be the same in pregnancy as in the nonpregnant state.[10] An LGI meal pattern may therefore represent an alternative strategy for reducing postprandial glycemia in GDM without restricting carbohydrate.[11]

The effect of an LGI eating pattern on obstetric outcomes in GDM has been little studied. Moses et al.[12] found that a significantly higher proportion of women in the higher-GI group met the criteria to commence insulin compared with women in the LGI group. In addition, 47% of the women in the high-GI group who met the criteria for insulin commencement avoided insulin by switching to an LGI diet. However, they found no significant differences in key fetal and obstetric outcomes.

To our knowledge, this study is the first randomized controlled trial to determine the efficacy of an LGI diet versus a conventional healthy diet on pregnancy outcomes in GDM. Our hypothesis was that an LGI diet would reduce birth weight (primary end point), birth weight centile, ponderal index, and the prevalence of LGA infants.

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