Up to one in four children in Dublin are deficient in vitamin D, the largest study of its kind in Ireland has shown.

Furthermore, this figure rises to one in three children in socio-economically disadvantaged areas.

Until now, studies on the vitamin D status of children in Ireland have been  limited, so scientists at Trinity College Dublin (TCD) set out to explore vitamin D deficiency by an accurate measure of socio-economic status. The study involved 1,226 children aged one to 17 years who had their vitamin D status tested at a Dublin hospital between 2014 and 2020.

About 90% of peak bone mass is attained in childhood and adolescence. Vitamin D is essential for the rapid bone growth that occurs at this time. It is also important for the adequate absorption of dietary calcium which is equally important for bone health.

The body creates vitamin D from direct sunlight on the skin. However, from October to March, we do not make enough vitamin D from sunlight in Ireland and food sources of naturally occurring vitamin D are limited.

Failure to maintain adequate vitamin D and calcium intake in childhood puts children at risk of osteoporosis later in life. Severe deficiency of vitamin D can also cause osteomalacia and lead to rickets in young children.

The study found that one in four children in Dublin were deficient in vitamin D and this rose to one in three in low socioeconomic areas.

Overall, a higher level of deficiency was found in girls and teenagers.

According to the study’s lead researcher, Helena Scully, a bone research fellow at the Mercer’s Institute for Successful Ageing (MISA) at St James’s Hospital, these findings are concerning as they may have long-term implications for bone health.

“In particular, girls, teens (over 12 years) and those living in low socioeconomic areas were most vulnerable. Choosing foods such as milk and cereal products with added vitamin D, and taking a supplement (10micrograms or 400units per day), particularly in the winter can help prevent low vitamin D levels,” she explained.

Meanwhile, according to one of the study authors and a consultant physician at St James’s Hospital, Dr Kevin McCarroll, this research shows that vitamin D deficiency is “just as prevalent in children as in adults, particularly during the teenage years when new bone mass is acquired”.

“Reduced sun exposure such as more sedentary behaviour or screen time and lower dietary vitamin D intakes are likely to be important factors,” he noted.

This research highlights the need to focus on strategies to improve vitamin D status in Irish children, especially in those found to be most at risk. The Food Safety Authority of Ireland recommends that everyone aged between 5-65 years should get 10 micrograms (400 units) of vitamin D - through diet and supplements - per day.

The study authors believe that the recommended daily allowance may need to include specific targets for children of between 10-15micrograms (400-600iu).

Systematic food fortification may also need to be considered, they added.

The study is published in the Journal of Nutritional Science and can be viewed here.