Vitamin D status and its determinants in pregnant women form the Faroe Islands

Abstract Background In regions like the Faroe Islands, where sunlight may be insufficient for vitamin D synthesis, alternative sources such as diet and supplements become crucial. This study focuses on assessing the vitamin D status of pregnant women in the Faroe Islands during the early second trimester, considering the potential implications for maternal and fetal health. Methods A nationwide cross-sectional study (June 2020-April 2022) with 652 women providing blood samples and a questionnaire on demographics, vitamin D intake, and diet. Binary logistic regression assessed predictors of low 25-hydroxyvitamin D (25OHD) levels (<50nmol/L). Plasma 25OHD concentrations were analysed at the local National Hospital using the Alinity i 25-OH Vitamin D assay, employing chemiluminescence microparticle immunoassay (CMIA) for quantitative determination. Results The mean age was 30.7 (SD, 4.9) years; 86% were locally born; 45% resided in the capital area; 49% were overweight (BMI ≥25.0), with a mean pre-pregnancy BMI of 26.0. Most participants (95%) reported vitamin D intake (median of 10µg/day) and consumed vitamin D-rich foods 5.3 times per week. Low 25OHD concentrations were observed in 26% of participants, associated with residency, vitamin D intake, dietary habits, overweight, and sampling time. Maternal age, education, BMI, smoking, and traditional food showed no significant associations. During winter, vitamin D intake correlated more strongly with plasma 25OHD levels (Spearman’s rho, winter: 0.4, p < 0.001; summer: 0.2, p = 0.002). Conclusions Our study’s findings are essential for the health of Faroese pregnant women. 74% of them had sufficient 25OHD levels, which is encouraging. However, low levels were associated with residence, diet, overweight, and winter. This underscores the need for public health efforts to focus on monitoring vitamin D status, promoting vitamin D-rich foods, especially in winter, and monitoring dietary intake to protect maternal and fetal health. Key messages • No previous data on vitamin D status in Faroese pregnant women. • Seasonal variation is observed.