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Providing perspectives on recent research into vitamins and nutritionals


New Clinical Study Shows Vitamin D Helps in Gestational Diabetes

By Julia Bird

Pregnant women want to have a healthy pregnancy. One increasingly prevalent pregnancy complication is gestational diabetes, which affects 2% to 20% of all pregnancies depending on geographic region. Gestational diabetes is a type of diabetes that is first detected during pregnancy (normally during the end of the second trimester) and usually subsides after delivery. It occurs due to metabolic changes in the woman’s body designed to help divert nutrients to the growing fetus. Women with gestational diabetes no longer respond effectively to the insulin that they produce after a meal, and blood glucose levels increase too much. These high glucose levels essentially “overfeed” the fetus, increasing the risk of birth complications. The newborn can also suffer from hypoglycemia after birth as it also produces large amounts of insulin to try to reduce the amount of glucose that is being transferred from the mother. In addition, women with uncontrolled diabetes are more likely to have higher circulating levels of inflammation markers and suffer from conditions such as pre-eclampsia.

The standard treatment involves dietary counseling to reduce glycemic load, and extra exercise to increase sensitivity of cells to the actions of insulin. Insulin injections or diabetes medication are given to women if they do not respond to lifestyle modifications. Vitamin D may also be important, as recent work has found that it improves both insulin secretion and sensitivity, and reduces inflammation (for background information, see recnt full access reviews from Chagas and Mezza). Low vitamin D levels are also a risk factor for gestational diabetes, as found by Aghajafari and co-workers. In the American Journal of Clinical Nutrition, the results of a randomized placebo-controlled trial with vitamin D on women with gestational diabetes are described by Asemi et al.

54 women with gestational diabetes were found in 950 pregnant women screened around week 26 of pregnancy, which meant that the rate of gestational diabetes was 5.7% in this population. The average vitamin D concentration was around 20 ng/ml (50 nmol/L) so it seems that at least half the women were sufficient, although the authors do not comment on whether any women in the study were clinically deficient. Women were provided with two large doses of vitamin D over the 6-week study period of 50,000 IU, equivalent to 2,400 IU per day. Aside from an increase in vitamin D levels due to supplementation, fasting plasma glucose, insulin, homeostasis model assessment (HOMA), quantitative insulin sensitivity check index (QUICKI), total cholesterol and LDL cholesterol measures improved over the study in the supplemented group. Markers of inflammation were not affected.

While this study did not look at health outcomes such as the proportion of large-for-gestational-age, or measures of infant or maternal morbidity such as pre-eclampsia, shoulder dystocia or hypoglycemia, it seems that there were improvements in glucose control and insulin sensitivity during the study that warrants further research. In the meantime, preventing vitamin D deficiency is always prudent, and increasing vitamin D levels may be a useful addition to lifestyle modification in reducing the negative effects of gestational diabetes.

Main citation:

Zatollah Asemi, Teibeh Hashemi, Maryam Karamali, Mansooreh Samimi, and Ahmad Esmaillzadeh. Effects of vitamin D supplementation on glucose metabolism, lipid concentrations, inflammation, and oxidative stress in gestational diabetes: a double-blind randomized controlled clinical trial. Am J Clin Nutr 2013 ajcn.072785; First published online October 16, 2013. doi:10.3945/ajcn.113.072785


Supporting citations:

Aghajafari F, Nagulesapillai T, Ronksley PE, Tough SC, O'Beirne M, Rabi DM. Association between maternal serum 25-hydroxyvitamin D level and pregnancy and neonatal outcomes: systematic review and meta-analysis of observational studies. BMJ. 2013 Mar 26;346:f1169. doi: 10.1136/bmj.f1169.

Chagas CE, Borges MC, Martini LA, Rogero MM. Focus on vitamin D, inflammation and type 2 diabetes. Nutrients. 2012 Jan;4(1):52-67. doi: 10.3390/nu4010052. Epub 2012 Jan 20.

Mezza T, Muscogiuri G, Sorice GP, Prioletta A, Salomone E, Pontecorvi A, Giaccari A. Vitamin D deficiency: a new risk factor for type 2 diabetes?. Ann Nutr Metab. 2012;61(4):337-48. doi: 10.1159/000342771. Epub 2012 Dec 3.