Lower vitamin D status in obese compared with normal-weight women despite higher vitamin D intake in early pregnancy

Obesity is associated with lower vitamin D concentrations than normal-weight. Pregnancy may affect vitamin D status, especially in obese subjects.

The purpose of this study was to compare vitamin D status and intake between obese and normal-weight women during pregnancy.

Twenty-five obese and 80 normal-weight women were recruited in the Western Sweden region (latitude 57°N). Blood samples and information on diet and sun exposure were collected in each trimester during pregnancy.

During summer months, 12% of normal-weight and 50% of obese women in the first trimester had serum 25(OH)D concentrations <50 nmol/L (P < 0.01). Supplement use, body fat mass, season of blood sampling, and travelling to southern latitudes were the most important determinants of vitamin D status. Obese women had higher reported dietary vitamin D intake in early pregnancy compared with normal-weight women. Usage of supplements containing vitamin D was 61% in early pregnancy and declined thereafter. Nine percent of normal-weight and 33% of obese women (P < 0.01) reported a dietary vitamin D intake according to national recommendations in the beginning of pregnancy.

Half of the obese women had what could be considered as suboptimal vitamin D status in early pregnancy and lower vitamin D status compared with normal-weight women despite reporting a higher dietary vitamin D intake. A majority of the women did not reach intake of vitamin D according to dietary recommendations.