Vitamin D Important for Health of Pregnant Women and their Children
As fall approaches and summer draws to a close in the northern hemisphere, it is timely to think about vitamin D. The Swedish Research Council and other funding sources were compelled by researchers interested in understanding the factors influencing maternal vitamin D status during pregnancy. Not surprisingly, since low serum 25(OH)D levels are associated with gestational diabetes and hypertension.
Brembeck and colleagues took blood samples from 95 fair-skinned pregnant women living in Sweden between gestational weeks 35 and 37. They measured serum 25(OH)D concentrations, 4 d dietary records, supplement use, sun exposure, skin type, BMI, and trips to southern latitudes. The average age was 32y. The mean body-weight gain during pregnancy was 13kg and 14% of the women were classified as overweight becoming pregnant (BMI > 25 kg/m2). The average serum 25(OH)D concentration was 47 nmol/L. Vitamin D status was highest in August (69 nmol/L) and lowest in April (33 nmol/L). The average daily dietary vitamin D intake was 6.1μg (244 IU) with total daily intake (food and dietary supplements) of 9.3μg (372 IU). During the winter months, 85% of the women had vitamin D levels < 50 nmol/L and 17% were below 30 nmol/L. The main determinants of vitamin D status were season, dietary supplement use, and traveling to southern latitudes.
Vitamin D supplementation (400 IU daily) for 9 weeks, beginning at week 25 of gestation, benefits moms. Supplementation increases serum 25(OH)D levels, reduces fasting plasma glucose and insulin concentrations, and lowers blood pressure in pregnant women. Brembeck and associates studied fair-skinned women. Skin pigmentation affects the amount of sun exposure needed for the body to synthesize 25(OH)D. Low vitamin D status is more prevalent in black women.
Low maternal vitamin D status during pregnancy impacts more than the woman’s health. Studies associate low maternal serum 25(OH)D levels with increased child’s risk of eczema and type 1 diabetes. Infants from mother’s with low vitamin D status (< 50 nmol/L) have higher mental and psychomotor scores at 14 months of age (vs mothers with serum 25(OH)D levels > 75 nmol/L during 1st trimester of pregnancy).
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