In a new randomized controlled trial, researchers in Iran have found that vitamin D during pregnancy reduces inflammation, improves glucose regulation and lowers blood pressure.
Asemi Z, Samimi M, Tabassi Z, Shakeri H, Esmaillzadeh A. Vitamin D Supplementation Affects Serum High-Sensitivity C-Reactive Protein, Insulin Resistance, and Biomarkers of Oxidative Stress in Pregnant Women. J Nutr. 2013
Being pregnant increases a woman’s chance that she will have higher C-reactive protein (CRP) levels in her blood. CRP is commonly measured to gauge levels of inflammation in the body.
Pregnancy also increases the likelihood that a woman will become resistant to insulin and experience elevated cholesterol levels, so they wanted to see if vitamin D helped in these departments, too.
These changes can lead to the development of many different health conditions, such as gestational diabetes, preeclampsia, premature birth, low birth weight, and DNA damage.
Because previous research has shown vitamin D may play a role in these conditions, researchers at Kashan and Isfahan Universities wanted to see if giving vitamin D supplements to pregnant women would improve their health. These same researchers previously published a paper showing that a high percentage of pregnant women in Iran are vitamin D deficient.
Fifty four pregnant women between the ages of 18 and 40 entered the study.
- 27 received a 400 IU pill of vitamin D per day for 9 weeks
- 27 received a placebo pill to take for the same amount of time
Both groups had been taking 400 mcg of folic acid since the beginning of pregnancy and 60 mg of iron since the beginning of the second trimester.
Height, weight, blood pressure, and blood samples were taken from all the women at the beginning of the study.
At the end of the study, the researchers found many significant differences between the women who took the vitamin D supplement and those who took the placebo. The women who took the vitamin D experienced:
- Higher blood levels of calcium and vitamin D.
- Decreases in CRP levels, which means their overall levels of inflammation went down.
- Increases in their plasma total antioxidant capacity (TAC) and glutathione (GSH) levels. This means their bodies were better able to resist oxidative damage and keep inflammation under control.
- Decreases in their fasting plasma glucose (FGP) and insulin levels. This means they were better able to regulate the levels of sugar in their blood, which reduced their chances of developing gestational diabetes.
- Decreases in both systolic and diastolic blood pressure. High blood pressure during pregnancy can increase the risk of complications in the mother and the baby.
All of the women entered the study in a vitamin D deficient state. After 9 weeks of supplementation with 400 IU of vitamin D per day, the average 25(OH)D level of the women in the vitamin D group rose to 21.5 ng/mL.
Even though the study was conducted during the summer months, the average vitamin D blood level of the women in the placebo group declined. The researchers cited cultural reasons as a likely explanation. Many women in Iran have limited opportunities for outdoor recreation and while outdoors they may wear conservative clothing and/or sunscreen.
It is impressive that only 400 IU of vitamin D produced such positive changes in multiple areas of the women’s health during their pregnancy. Future studies that give higher doses of vitamin D should clarify what the optimal dose is during pregnancy, as it is likely much higher than 400 IU/day. However, this study highlights that women need to get some vitamin D, as even just a little is much better than getting none.