Could the 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) affects the risk of gestational diabetes mellitus (GDM).

Study: Adherence to the 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 the effective use of insulin. GDM can increase the risk of several adverse short-term and long-term outcomes for both mother and baby; therefore, it is essential to control blood glucose levels during pregnancy through medical and nutritional interventions.

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

MedDiet involves eating higher amounts of whole grains, vegetables, legumes, and foods rich in monounsaturated fatty acids (MUFAs) and a reduced intake of processed and red meat. While it is important to understand how individual food components affect GDM, it may be more beneficial to consider whole dietary patterns such as the MedDiet in managing this condition.

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

About the study

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

Ten articles published between 2012 and 2023 were finally considered for 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 of these studies were pooled and amounted to 32,959,909, and were aged between 18 and 45.

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

Results of the study

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

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

Subgroup analysis found that the association between adherence to the MedDiet and reduced 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 results in higher consumption of whole grain products, fruits, vegetables, extra virgin, nuts, olive oil, and legumes with regular intake of fish and seafood. A higher intake of antioxidants and vitamins through this diet reduces oxidative stress and systemic inflammation, both of which are critical factors in the development and progression of chronic disease.

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

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

Some studies have also shown that consumption of 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 red meat consumption increases the risk of GDM, which may contribute to the reduced risk of GDM in individuals who also follow the MedDiet.

Conclusions

The current systematic review and meta-analyses showed a strong link 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 reproductive age to prevent the development of GDM and other adverse outcomes of pregnancy.

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