Effects Of Dietary Intervention On Glycemic Control And Diabetes-related Factors In Patients With Type2Diabetes And Gestational Diabetes:Meta-analyses Of Randomized Controlled Trials

Diabetes mellitus (DM) belongs to nutrition-related disease, type2diabetes mellitus (T2DM) and gestational diabetes mellitus (GDM) are the two commom types of DM. In recent years, with the changes of lifestyle and dietary pattern, the incidences of T2DM and GDM have been increasing. Consequently, the increases in T2DM-related complications and GDM-related adverse pregnancy outcomes have led to severity of social resources and healthcare expenditures. Thus, the primary therapy is control the glucose of T2DM and GDM, and prevention the adverse complications.Many diabetes guidelines have pointed out medical nutrition therapy is considered basic method for the treatment of diabetes. Nowadays the medical nutrition therapy has been changed from single nutrient to mixed dietary patterns. Therefore, assessment the dietary patterns have had a more meaningful influence in patients with T2DM and GDM. Mediterranean diet has been explored widely in diabetes and cardiovascular disease, however, whether Mediterranean diet improves glucose metabolism are inconsistent. Hence, the first part of our study was to conduct a meta-analysis of randomized controlled trials to explore the effects of Mediterranean diet on glycemic control, weight loss and cardiovascular risk factors in T2DM patients. For the treatment of GDM, there were some clinical trials which explored the influence of different dietary patterns on GDM, but there is little evidence-based medicine to prove which dietary pattern can improve glucose metabolism and pregnancy outcomes in GDM patients. Hence, the second part of our study was to conduct a meta-analysis of randomized controlled trials to evaluate the effects of different dietary approaches on glycemic control and pregnancy outcomes in GDM patients.Part One Effects of Mediterranean-style diet on glycaemic control, weight loss and cardiovascular risk factors among type2diabetes individualsObjectives:Some studies suggest that Mediterranean diet may improve glucose metabolism in patients with type2diabetes mellitus (T2DM), but the results are inconsistent. We conduct a meta-analysis of randomized controlled trials to explore the effects of Mediterranean diet on glycemic control, weight loss and cardiovascular risk factors in T2DM patients.Methods:We performed searches of EMBASE, Cochrane Library, and PubMed databases up to February2014. We included randomized controlled trials that compared the Mediterranean diet with control diets in patients with T2DM. Outcomes measures were glycemic control, weight loss,and cardiovascular risk factors. The outcomes of glycemic control including hemoglobin A1c (HbA1c), fasting plasma glucose (FPG), fasting insulin, and insulin resistance (HOMA-IR); the outcomes of weight control including body weight, body mass index (BMI), and waist circumference; the outcomes of cardiovascular risk factors including total cholesterol, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and blood pressure.Effect size was estimated as weighted mean difference (WMD) with95%confidence intervals (CIs) by using random effects models. Results:The meta-analysis included nine studies with1178patients. Compared with control diets,Mediterranean diet led to greater reductions in HbAlc (WMD:-0.30%;95%CI:-0.46,-0.14%), FPG (WMD:-0.72mmol/L;95%CI:-1.24,-0.21mmol/L), and fasting insulin (WMD:-0.55μU/ml;95%CI:-0.81,-0.29μU/ml).Furthermore, Mediterranean diet had significant reductions in BMI (WMD:-0.29kg/m2;95%CI:-0.46,-0.12kg/m2) and body weight (WMD:-0.29kg;95%CI:-0.55,-0.04kg). Additionally, Mediterranean dietwas effective in improving cardiovascular risk factors, including reductions in total cholesterol (WMD:-0.14mmol/L;95%CI:-0.19,-0.09mmol/L), triglyceride (WMD:-0.29mmol/L;95%CI:-0.47,-0.10mmol/L), and increase in high-density lipoprotein cholesterol (WMD:0.06mmol/L;95%CI:0.02,0.10mmol/L);similarly, MSD was associated with a decline of1.45mm Hg (CI-1.97to-0.94) for systolic blood pressure and1.41mm Hg (CI-1.84to-0.97) for diastolic blood pressure. However, there were no significant differences in HOMA-IR, waist circumference, and low-density lipoprotein cholesterol.Conclusions:The present meta-analysis provides evidence that MSD improves outcomes of glycemic control, body weight and cardiovascular risk factors in T2DM patients. Part Two Effects of different dietary approaches on glycemic control and pregnancy outcomes in patients with gestational diabetes mellitusObjectives:Medical nutrition therapy is considered the cornerstone for the treatment of gestational diabetes mellitus (GDM). But there is little evidence-based medicine to prove which dietary intervention can improve glucose metabolism and pregnancy outcomes in GDM patients. We conduct a meta-analysis of randomized controlled trial (RCTs) to evaluate the effects of different dietary approaches on glycemic control and pregnancy outcomes in GDM patients.Methods:We searched PubMed, Cochrane Library, and EMBASE databases up to January2015. We included RCTs with dietary interventions to the management of GDM. Outcomes measures were glycemic control and pregnancy outcomes. The outcomes of glycemic control included fasting plasma glucose (FPG), postprandial glucose (PG), and insulin requirement; maternal outcomes included maternal weight gain, maternal body mass index (BMI) gain, cesarean section, labor induction, and shoulder dystocia; neonatal outcomes included preterm birth, macrosomia, small-for-gestational age(SGA), large-for-gestational age(LGA), birth weight, neonatal hypoglycemia, and low Apgar score.For dichotomous variables, we used relative risk (RR) with95%confidence intervals (CIs) as the effect size. For continuous variables, we chose weighted mean difference (WMD) with95%CIsas the effect size.Results:The meta-analysis included a total of18RCTs with1498GDM patients. We assessed five different types of dietary approaches:low glycemic index (GI) diet, energy-restricted diet, Dietary Approaches to Stop Hypertension (DASH) diet, carbohydrate-restricted diet, and fiber-enriched diet.1. Low-GI diet analyses included five RCTs with401patients. Compared with control diet, low-GI diet had significant reductions in FPG (WMD:-0.152mmol/L;95%CI:-0.303,-0.001mmol/L), the use of insulin (RR:0.768;95%CI:0.599,0.985), and birth weight (WMD:-161.776g;95%CI:-245.953,-77.599g); however, there were no significant differences in PG, maternal weight gain, cesarean section rate, macrosomia, the rate of preterm birth, LGA, and SGA.2. Five RCTs (n=639patients) evaluated the effects of energy-restricted diet. Compared with control diet, energy-restricted diet led to greater reductions in FPG (WMD:-0.646mmol/L;95%CI:-0.882,-0.410mmol/L), PG (WMD:-0.689mmol/L;95%CI:-1.283,-0.095mmol/L), and birth weight (WMD:-96.563g;95%CI:-191.635,-1.492g); no significant difference was seen in maternal weight gain, cesarean section rate, labor induction rate, shoulder dystocia rate, neonatal hypoglycemia, macrosomia, LGA, and low Apgar score.3. Two RCTs involving92women with GDM contributed data to assess the effects of DASH diet. Compared with control diet, DASH diet significantly decreased the use of insulin (RR:0.276;95%CI:0.143,0.531), rate of cesarean section (RR:0.556;95%CI:0.393,0.786), and birth weight (WMD:-581.212g;95%CI:-790.239,-372.185g); there were no significant differences in maternal weight gain and maternal BMI gain. No data about other outcomes were available for further analyses..4. Carbohydrate-restricted diet analyses included four RCTs with308GDM patients. Compared with control diet, carbohydrate-restricted diet was associated with a decline of0.285mmol/L (95%CI:-0.565,-0.005mmol/L) for PG and0.883kg (95%CI:-1.558,-0.208kg) for maternal weight gain; no significant difference was found regarding FPG, the use of insulin, rate of cesarean section, birth weight, macrosomia, and LGA.5. Two RCTs involving58GDM patients provided data to assess the effects of fiber-enriched diet. Compared with control diet, fiber-enriched diet had no significant difference in FPG (WMD:-0.043mmol/L;95%CI:-0.432,0.345mmol/L); there was no available data on other outcomes for further analyses.Conclusions:Our study provides evidence that low-GI diet, energy-restricted diet, DASH diet, and carbohydrate-restricted diet can improve glycemic control and part of pregnancy outcomes in patients with GDM.1. Regarding glycemic control outcomes:low-GI diet, energy-restricted diet, DASH diet, and carbohydrate-restricted diet have a prominent role in improving glucose metabolism; of these, energy-restricted diet was associated with greatest reductions in FPG and PG; and DASH diet was associated with greatest reductions in the need for insulin among GDM patients.2. Regarding maternal and neonatal outcomes:low-GI diet had a significant reduction in birth weight; energy-restricted diet significantly decreased the birth weight; DASH diet had significant reductions in cesarean section rate and birth weight; carbohydrate-restricted diet led to a less gain of maternal weight during pregnancy; of these, DASH diet was most effective in reducing birth weight.