The Helmholtz Centre for Environmental Research and the Martin Luther University in Halle-Wittenberg in Germany sought out to prove that there is a correlation between the concentration of vitamin D in the blood of expectant mothers and in the cord blood of babies. Cord blood is the blood that remains in the placenta and in the attached umbilical cord after childbirth.

Vitamin D is known to help strengthen bones, protect against infections during the winter, and aid the nervous and muscular systems. However, some studies have questioned the positive aspects of the vitamin.

During the latest study, researchers looked at the association between vitamin D levels during pregnancy and at birth, the immune status and allergic diseases of the children later in life. They included 622 mothers and their 629 children in the long-term study.

Researchers tested the level of vitamin D in the blood of the pregnant mothers, and also in the cord blood of the children born. They also sent out questionnaires to mothers in order to assess the occurrence of food allergies during the first two years of the children’s lives. They found that in cases where expectant mothers were found to have a low vitamin D level in the blood, food allergies among their two-year-old children was less likely, compared to children whose mothers had a higher vitamin D level at the time of pregnancy.

Children with those allergies were found to have a higher level of specific immunoglobulin E to food allergens like egg white, milk protein, wheat flour, peanuts or soy beans.

Researchers also looked at the immune response of the affected children and analyzed regulatory T-cells, white blood cells known as lymphocytes, in cord blood. These cells can prevent the immune system from overreacting to allergens, helping to protect against allergies. They found that the higher the level of vitamin D found in the blood of mothers and children, the less regulatory T-cells could be detected. The team suggests that this correlation could mean that vitamins D suppresses the development of regulatory T-cells, increasing the risk of allergy.

“Based on our information, an excess of vitamin D can increase the risk of children developing a food allergy in the first two years of their life,” said Dr. Kristin Weiße from the Helmholtz Centre for Environmental Research in Leipzig.

She said that the level of vitamin D is mainly affected by how much time you spend outdoors. Although they did find a correlation between vitamin D and food allergies, she said many other factors could have been at play as well.

A study published in the journal PLOS Medicine in February found that obese people may have a deficiency in vitamin D. Dr Elina Hypponen, with the University College London’s Institute of Child Health, and colleagues discovered a connection between the vitamin deficiencies and weight gain after analyzing genetic markers for 42,000 people. They believe that the excessive amount of fat which accompanies obesity is to blame for the vitamin D deficiency.