Objectives. To evaluate the relationship of vitamin D intake and pro-inflammatory cytokines (TNF-α and IL-6) in overweight and obese pregnant women.
Subjects. Forty-eight overweight and obese pregnant subjects (pre-pregnancy body mass index (BMI) > 25 kg/m2) in their third trimester between 18 and 40 years old were recruited mainly through fliers and ads in magazines.
Methods. This cross-sectional study included 48 pregnant women in the third trimester (16 overweight and 32 obese). Dietary vitamin D intake (DD) measures of the subjects were obtained from 24 hr dietary recall conducted using NDSR. Total vitamin D intake (TD) was calculated by adding dietary vitamin D intake and supplemental vitamin D intake. Women were classified into low and high DD groups (< and ≥5 mcg of vitamin D intake) according to the dietary intake. They were also classified into low TD and high TD intake groups based 50th percentile frequency of total vitamin D intake. Plasma concentrations of pro-inflammatory cytokines (TNF-α and IL-6) were determined by enzyme-linked immunosorbent assay (ELISA) using MilliplexTM Multiplex kits (Millipore, Billerica, MA) according to manufacturer’s protocol. Associations between pre-pregnancy BMI, vitamin D intake, and inflammatory markers were evaluated by bivariate correlation analysis, two-way ANOVA, and non-parametric Mann-Whitney U test.
Results. There was no relationship between pre-pregnancy BMI and vitamin D intake. Pre-pregnancy BMI was positively correlated to IL-6 (r=+0.295, P<0.05). There was a trend for a relationship between total vitamin D intake and TNF-a. Dietary vitamin D intake was significantly different between low DD (n=38) and high DD (n=10) groups (P=0.000). Total vitamin D intake (TD) was significantly different between low TD (n=24) and high TD (n=24) groups (P=0.000). The difference between the mean levels of TNF-α in low TD and high TD groups had a slight trend (P=0.08) with high TD having lower TNF-α levels There were no significant main and interaction effects of pre-pregnancy BMI and vitamin D on the levels of inflammatory markers (TNF-α, IL-6).
Conclusion. There was no significant relationship between vitamin D intake and markers of inflammation. There were no interactive effects of pre-pregnancy BMI and vitamin D on inflammation. However, the result of a trend for a relationship between total vitamin D intake and TNF-a shows that further investigation is required to analyze the relationship between vitamin D (using serum 25-OHD concentrations) and markers of inflammation.