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Vitamin D during pregnancy and overweight in boys

Vitamin D during pregnancy and overweight in boysDuring a woman’s pregnancy, vitamin D is important for the growth, development, and general health of the baby. Apparently, maternal vitamin D deficiency during pregnancy increases the risk of boys developing more fat tissue during their first years of life, which makes them more prone to overweight in childhood and later in life. This was reported in a Spanish population study that is published in Nutrients. Because both overweight and vitamin D deficiency are so widespread, it is essential for pregnant women to make sure as a minimum to follow the official recommendations for vitamin D supplementation. Also, there is no read to avoid sun exposure because sunshine is our primary vitamin D source during the summer period. Just make sure not to get a sunburn.

In their new study, the Spanish researchers gathered data from the INMA (Infancy y Medio Ambiente) population study that has followed several thousand children from birth until adulthood in order to study how environmental factors such as diet, pollution, and other things affect their growth and development. The new study included 2,027 mother-and-child couples. The vitamin D status of the expecting mothers was measured in the 13th week of pregnancy. At ages seven and 11 years, the children’s weight in relation to their height was recorded, a measure that is defined as z-score body mass index (zBM). At age 11 years, the children’s fat percentage was also calculated.
It turned out that around 17 percent of the pregnant women lacked vitamin D, while around 40 percent of the children at both ages were overweight. Moreover, the maternal vitamin D deficiency during pregnancy particularly influenced the growth and development of boys. There was also a direct link between having a higher zBMI, a higher fat percentage, and an increased risk of being overweight. There was also an increased risk of low birth weight, which was accompanied by a greater, undesirable weight gain in childhood. The researchers concluded that lack of vitamin D during the early part of pregnancy affects boys’ fat distribution and weight later in life.

Why does maternal vitamin D deficiency affect boys and girls differently?

Although several studies have shown a link between maternal vitamin D deficiency during pregnancy and the growth and health of the child, the new Spanish population study is the first to show that maternal vitamin D deficiency tends to affect the fat percentage and weight of boys, in particular.
The researchers are not able to explain why boys and girls are affected differently. However, animal studies and in vitro studies suggest that maternal vitamin D deficiency during pregnancy influences boys’ testosterone levels and related metabolic processes.

Recommendations for vitamin D in pregnancy

According to the Danish Health Authority, pregnant women should take 10 micrograms of vitamin D per day all year round. It is also advisable for women planning to become pregnant to have their vitamin D status measured in order to help them reach optimal blood levels of the nutrient. According to the European Food Safety Authority (EFSA), the safe upper intake level for vitamin D is 100 micrograms for adults, including pregnant and breastfeeding women.

Reasons why vitamin D deficiency is so common among women of childbearing age and pregnant women

  • Lack of summer sun
  • Overuse of sunscreen that blocks the skin’s vitamin D synthesis
  • Low-fat diets – especially if they exclude oily fish and eggs
  • Having dark skin
  • Alcoholism
  • Overweight and diabetes
  • Use of cholesterol-lowering medicine and certain other medical drugs
  • Failure to stick diligently with the recommendations for vitamin D supplementation


Julia Sanguesa et al. Prenatal Vitamin D Levels Influence Growth and Body Composition until 11 Years in Boys. Nutrients 2023

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