Could a Mediterranean diet be the secret to avoiding gestational diabetes?

In a recent study published in the journal Nutrition & Diabetes, researchers investigate whether the Mediterranean diet (MedDiet) influences the risk of gestational diabetes mellitus (GDM).

Study: Adherence to Mediterranean dietary pattern and the risk of gestational diabetes mellitus: A systematic review and meta-analysis of observational studies. Image Credit: Olga Gavrilova / Shutterstock.com

GDM and MedDiet

GDM is a common disorder that occurs during pregnancy due to placental hormones that prevent effective insulin utilization. GDM can increase the risk of several short- and long-term adverse outcomes for both the mother and child; therefore, it is crucial to control blood glucose levels during pregnancy through medical and nutritional interventions.

Several studies have suggested that preventing GDM through lifestyle and dietary interventions in pre-pregnancy or early pregnancy stages could significantly reduce the risk of neonatal diseases and congenital disabilities, as well as improve the mother’s health. Typically, increased consumption of saturated fatty acids, carbohydrates, cholesterol, and total fat increases the risk of developing GDM.

MedDiet is associated with consuming higher amounts of whole grains, vegetables, legumes, and foods rich in monounsaturated fatty acids (MUFAs) and reduced intake of processed and red meat. Although it is important to understand how individual food components affect GDM, assessing overall dietary patterns like the MedDiet could be more beneficial in managing this condition.

Several studies have indicated that adherence to the MedDiet reduces the risk of GDM. Although many studies have equivocally highlighted the benefits of MedDiet in lowering the risk of GDM, a systematic review and meta-analysis are needed to summarize the findings of the available research.

About the study

For the current systematic review and meta-analysis, all relevant literature published until August 2023 was obtained from PubMed, Web of Science, Google Scholar, and Scopus databases. Duplicate, animal, and ecological-based research, short communications, and non-English language studies were excluded.

Ten articles published between 2012 and 2023 were ultimately considered for the analysis, which included two case-control and eight cohort studies. These studies were conducted in different countries, including the United States, the Mediterranean countries, Australia, Iran, Spain, and Greece. The participants of these studies were pooled and totaled 32,959,909, with ages ranging between 18 and 45.

MedDiet adherence was assessed through a Mediterranean Diet Adherence Screener (MEDAS) score, higher quartiles of alternate MED (AMED) score, and a Mediterranean-Style Dietary Pattern Score (MSDPS). GDM outcomes were determined using the National Diabetes Data Group criteria, fasting or postprandial blood sugar levels, or glucose challenge test using the Obstetricians and Gynecologists (HSOG) criteria.

Study findings

Seven of the ten reviewed indicated that higher adherence to the MedDiet reduces the risk of GDM. Moreover, the pooled analysis identified a significant correlation between adherence to MedDiet and a reduced risk of GDM. Across all studies, these results were heterogeneous, which could be due to differences in study design or period of dietary assessment.

Although case-control studies reported a more significant 75% reduction in the likelihood of GDM in women with greater adherence to the MedDiet, cohort studies revealed a moderate 20% reduction in the risk of GDM. A significantly higher reduction in GDM risk in case-control studies could be attributed to recall biases that are difficult to validate, which may lead to an overestimation of the risk ratio.

A subgroup analysis found that the association between adherence to the MedDiet and reduction of GDM risks was true for both Mediterranean and non-Mediterranean countries. Thus, the MedDiet appears to benefit both Mediterranean and non-Mediterranean populations.

Greater adherence to the MedDiet leads to higher consumption of whole grain products, fruits, vegetables, extra virgin, nuts, olive oil, and legumes with regular fish and seafood intake. A higher intake of antioxidants and vitamins through this diet reduces oxidative stress and systemic inflammation, both of which are crucial factors in the development and advancement of chronic diseases.

The high polyphenol content in fruits and vegetables also significantly reduces GDM risk through several mechanisms, such as inhibition of glucose absorption in the gastrointestinal tract, anti-inflammatory effects, modification of microbiota, and increased antioxidant capacity.

Obesity and insulin resistance, both common risk factors for GDM, are inversely related to the MedDiet. One previous meta-analysis revealed that greater adherence to the MedDiet reduces the risk of obesity or overweight by 9%.

Several studies have also shown that the consumption of whole grains reduces the risk of developing type 2 diabetes. Furthermore, nuts contain MUFAs and polyunsaturated fatty acids (PUFAs) that can regulate blood glucose levels and reduce appetite.

Observational studies have indicated that long-term red meat consumption increases GDM risk, which may also contribute to the reduced risk of GDM in individuals who follow the MedDiet.

Conclusions

The current systematic review and meta-analyses presented a robust association between high adherence to the MedDiet before gestation or during pregnancy and reduced GDM risk. Thus, MedDiet should be recommended to women of reproductive age to prevent the development of GDM and other adverse pregnancy outcomes.

Nevertheless, future studies are needed to analyze the interaction of the MedDiet, genetic, and lifestyle risk factors of GDM to develop more effective preventive strategies.