Women should avoid taking vitamin D supplements while pregnant as these may increase the risk of their children developing food allergies by the age of two, a new study suggests.

Vitamin D is essential for healthy bones, but is present in very few foods. It is also known as the sunshine vitamin, because it is made in the body when ultraviolet rays from sunlight strike the skin. However, Ireland's northerly latitude and lack of winter sunlight means that we cannot make enough vitamin D in this way. As a result, some people choose to take supplements.

According to German scientists, while the benefits of the vitamin are widely acknowledged, a potential link between it and the development of allergies began to be investigated at the end of the 1990s.

They decided to look into this further and set out to see whether vitamin D levels found in pregnant women could affect the risk of allergies in their children.

They looked at 622 mothers and 629 children. Levels of the vitamin were measured in the blood of the pregnant women and in the umbilical cord blood of the children after they were born.

The children were then monitored for two years to see if any allergies developed.

The study found that mothers who had low levels of vitamin D in their blood were less likely to have children who went on to develop food allergies.

In other words, women with high levels of the vitamin in their body during pregnancy were more likely to have children who went on to develop allergies to certain foods.

The scientists noted that affected children were particularly likely to develop allergies to egg white, wheat flour, milk protein, soya beans and peanuts.

They also found that children whose mothers had high levels of the vitamin in their blood had fewer regulatory T-cells. These cells help to protect the body against allergies. The scientists suggested that vitamin D may suppress the development of these cells, increasing the risk of an allergy.

The team advised women not to take vitamin D supplements when pregnant.

"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."

Details of these findings are published in the journal, Allergy.

For more information on pregnancy, see our Pregnancy Clinic here