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

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

Study: Adherence to a Mediterranean diet and the risk of gestational diabetes: a systematic review and meta-analysis of observational studies. Image credit: Olga Gavrilova / Shutterstock.com

GDM and MedDiet

GDM is a common condition that occurs during pregnancy due to placental hormones that prevent effective insulin use. GDM can increase the risk of several short- and long-term adverse outcomes for both the mother and the baby; 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 the pre-pregnancy or early pregnancy stages can significantly reduce the risk of neonatal diseases and birth defects, and improve maternal health. In general, increased consumption of saturated fatty acids, carbohydrates, cholesterol, and total fat increases the risk of developing GDM.

The 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. While it is important to understand how individual food components affect GDM, assessing overall dietary patterns such as the MedDiet may be more useful in managing this condition.

Several studies have shown that adherence to the MedDiet reduces the risk of GDM. Although many studies have equivocally emphasized the benefits of the MedDiet in reducing 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 up to August 2023 was retrieved from the databases PubMed, Web of Science, Google Scholar and Scopus. Duplicate, animal and ecological studies, short communications and non-English studies were excluded.

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

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

Research results

Seven out of ten studies included indicated that higher adherence to the MedDiet reduces the risk of GDM. Furthermore, the pooled analysis identified a significant correlation between adherence to the MedDiet and a reduced risk of GDM. In 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 showed a modest 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, leading to an overestimation of the risk ratio.

A subgroup analysis showed that the association between adherence to the MedDiet and reduction in GDM risk held for both Mediterranean and non-Mediterranean countries. Thus, the MedDiet seems to benefit both Mediterranean and non-Mediterranean populations.

Greater adherence to the MedDiet leads to higher consumption of whole grains, fruits, vegetables, extra virgin, nuts, olive oil and legumes with regular intake of fish and seafood. 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 progression of chronic diseases.

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

Obesity and insulin resistance, both common risk factors for GDM, are inversely related to the MedDiet. A 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 consuming whole grains reduces the risk of developing type 2 diabetes. In addition, nuts contain MUFAs and polyunsaturated fatty acids (PUFAs) that can regulate blood glucose levels and reduce appetite.

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

Conclusions

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

However, future studies are needed to analyze the interaction of the Mediterranean diet, genetic factors, and lifestyle risk factors for GDM so that more effective prevention strategies can be developed.