A new study published in the journal Nutrients examines the role of medically directed nutritional patterns and supplements in managing gestational diabetes mellitus (GDM).

Study: Gestational diabetes mellitus: what can medical nutrition therapy do? Image Credit: BaLL LunLa / Shutterstock.com

About GDM

GDM affects between 1-30% of pregnant women, with its prevalence varying widely between regions. Typically, GDM is diagnosed by an abnormal oral glucose tolerance test (OGTT) between 24 and 28 weeks. GDM is consistent with fasting, one-hour, and two-hour glucose levels exceeding 92 mg/dL, 180 mg/dL, and 153 mg/dL, respectively.

GDM often arises due to impaired beta cell function. Beta cells are pancreatic cells that become unable to secrete additional insulin in response to the demands of pregnancy, thereby raising blood sugar levels.

Insulin resistance (IR) is common during pregnancy, as a consistent supply of glucose to the developing fetus is needed for its energy source. Towards the end of pregnancy, IR becomes nearly as high as levels observed in people with type 2 diabetes mellitus (T2DM). Nevertheless, following childbirth, the mother’s insulin sensitivity may either revert to normal or continue to be impaired with eventual T2DM.

The consequences of GDM affect both mother and fetus and can include macrosomia, stillbirth, and metabolic aberrations for the newborn. For the mother, the long-term risk of diabetes and cardiovascular disease (CVD) is increased. Moreover, GDM contributes to over 87% and 16% of fetal hyperglycemia and newborn GDM cases, respectively.

What is medical nutrition therapy?

Medical nutrition therapy (MNT) refers to nutritional supervision to regulate the body’s metabolic status. MNT, which often includes food and nutrients, is effective in managing various chronic medical conditions. This treatment is also relatively inexpensive and is preferred to drug therapy as the treatment of choice in GDM.

MNT in GDM maintains healthy blood sugar levels, improves insulin sensitivity, and reduces the risk of multiple adverse pregnancy outcomes. Moreover, MNT protects the fetus from oxidative stress, prevents macrosomia, and reduces the risk of maternal hypertension following childbirth.

Energy intake

The lack of international guidelines for energy intake in GDM has led to the application of general recommendations for these patients. These include a total intake of 1,800 kcal/day that can be increased in the second and third trimesters as needed to maintain normal weight gain and metabolic parameters.

According to the International Federation of Gynecology and Obstetrics (FIGO), total calorie intake should be 30-35 kcal/kg/day. Severe calorie restriction to less than 1,500 kcal/day is not advisable, as it may induce ketosis, as well as impair fetal growth and development.

Carbohydrate intake

Carbohydrate intake should contribute to 35-55% of total energy intake, depending on the geographical context. For example, Chinese patients have a higher proportion of carbohydrates in their recommended diets.

The glycemic index (GI) is key to determining post-meal blood sugar levels. Low-GI diets are correlated with better blood glucose control, controlled weight gain during pregnancy, and improved insulin sensitivity. The safety of a low-GI diet has also been reported; however, more research is needed to confirm its effectiveness as an intervention for GDM.

Protein intake

Protein regulates energy homeostasis, produces satiety, and is essential for both growth and development. A high-protein diet may impair insulin sensitivity and increase the risk of GDM. Plant protein is preferable to animal protein in lowering GDM risk.

Fat intake

Fatty acids are essential in regulating glucose metabolism. Excess fat in the bloodstream may induce insulin resistance by suppressing the uptake of blood glucose into peripheral tissues in response to insulin.

Under normal conditions, fats should comprise 30-40% of total energy. Since carbohydrate intake is restricted in GDM, fat intake often increases and may predispose these patients to obesity, as reported in earlier studies reporting higher triglyceride levels in women with GDM. Nevertheless, plant fats may reduce the risk of GDM when substituted for carbohydrates.

Insulin sensitivity can be improved by n-3 long-chain polyunsaturated fatty acids (LCPUFAs) like docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), both of which are found in the microscopic ocean fauna krill. These fats may also alleviate GDM-associated changes in fetal neurodevelopment.

Vitamins and minerals

Folate and vitamin B12 are essential coenzymes for multiple metabolic reactions. Their deficiency is associated with some types of anemia, DNA damage, and abnormal neurodevelopment.

During pregnancy, folate and B12 must be simultaneously supplemented to avoid the adverse impact of folate accumulation. Folate at high levels without B12 adequacy may increase the risk of GDM; however, the underlying mechanism remains unclear.

Vitamin D is commonly deficient at all stages of life. Nevertheless, it is crucial for a successful pregnancy and fetal bone and brain development. Vitamin D supplementation has also been shown to reduce the risk of GDM, which may be due to its role in glucose homeostasis and insulin secretion.

Iodine is central to thyroid hormone production, thus demonstrating its essential role in a healthy pregnancy. Both excess and inadequate iodine levels may impair thyroid function and increase the risk of GDM.

Conclusions

Any dietary program can be successful in treating GDM when used in combination with physical exercise. Despite previous reports of how GDM can be managed through different diets, there remains a lack of published guidelines on the specific food products that can be used to manage this pregnancy complication.

Thus, future studies are needed to develop individualized protocols for managing GDM and explore the potential utility of novel foods like krill that may support this goal.