During pregnancy, the placenta stimulates the release of many hormones that increase the amount of sugar in the blood. Usually, the pancreas is able to release enough insulin to manage higher blood sugar levels. However, after prolonged exposure to high blood sugar, the pancreas is unable to keep up, and gestational diabetes can occur. Gestational diabetes (GDM) is a reversible form of diabetes that occurs only in pregnant women and usually ceases with birth. Approximately 3-5% of women will develop GDM during the course of their pregnancy. GDM can can place mothers and their babies at risk for adverse health outcomes such as type II diabetes, preeclampsia, cesarean delivery, high birth weight, respiratory distress and in the most serious cases, birth defects.
Managing this condition throughout pregnancy is crucial to reduce the risk of later complications. Similarly to non-gestational diabetes, GDM can be mediated by controlling glucose intake, monitoring blood glucose levels, maintaining a healthy diet and exercising regularly. Managing these lifestyle factors plays a part in the regulation of the metabolic markers associated with diabetes and GDM.
Past research has linked vitamin D to metabolic markers associated with diabetes and GDM, such as fasting insulin, blood glucose levels, insulin resistance and lipid profiles. However, the available research on the effect of vitamin D on glucose metabolism and lipid profiles in women with GDM remain inconsistent. Therefore, researchers conducted a meta-analysis of randomized controlled trials (RCT) to evaluate the role of vitamin D on metabolic markers in women with GDM.
The researchers included a total of 6 RCTs that evaluated the role of vitamin D supplementation on metabolic profiles of pregnant women with GDM. The following metabolic markers were assessed in this meta-analysis: fasting plasma glucose (FPG) HOMA-IR, HOMA-B, QUICKI, HbA1c, insulin levels, triglycerides, LDL cholesterol, HDL cholesterol and total cholesterol were included in this meta-analysis. HOMA-IR, HOMA-B and HbA1c are all general markers of glucose metabolism, with higher levels indicating impaired insulin sensitivity and blood glucose levels over long periods of time.
This is what the researchers found:
- Vitamin D supplementation significantly reduced HOMA-IR (95 % CI, − 1.14 to − 0.18) and HOMA-B (95 % CI, − 0.79 to − 0.25).
- Supplementation significantly increased QUICKI, a measurement of insulin sensitivity (95 % CI, 0.26 to 1.20). Higher score of QUICKI indicates increased insulin sensitivity.
- Vitamin D supplementation did not affect metabolic markers such as FPG, insulin or HbA1c.
- Vitamin D supplementation significantly reduced LDL-cholesterol levels (95 % CI, − 0.58 to − 0.07).
- Vitamin D supplementation did not significantly improve total cholesterol, HDL cholesterol or triglycerides concentrations.
The researchers concluded:
“This meta-analysis has demonstrated that vitamin D supplementation may lead to an improvement in HOMA-IR, QUICKI, and LDL-cholesterol levels…”
“…Additional prospective studies regarding the effect of vitamin D intake on glucose homeostasis parameters and lipid profiles in GDM women are necessary.”
As always, it is important to note the study’s limitations. The researchers did not review the relationship between vitamin D status and metabolic markers in GDM. Also, they did not reveal the vitamin D dosage that was being administered to those participating in the RCTs. In the past, similar studies have used a variety of doses. Such variation between doses make it difficult to draw specific conclusions on the effect of vitamin D in those with GDM.
Despite these limitations, the study provides additional evidence that supplementing with vitamin D helps support the health of pregnant mothers. The Vitamin D Council recommends women who are pregnant or breastfeeding supplement with 4,000 – 6,000 IU vitamin D3 per day.
There is a need for further studies on this matter to determine the optimal dose of vitamin D for pregnant women with gestational diabetes.
Peterson, R. & Cannell, JJ. Does vitamin D supplementation aid in the management of gestational diabetes? 7/2017.
Akbari, M. et al. The Effects of Vitamin D Supplementation on Glucose Metabolism and Lipid Profiles in Patients with Gestational Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Hormone Metabolism Research, 2017.