Dublin’s vitamin D map shows major differences in deficiency rates

Posted on: 02 November 2016

For the first time in Ireland, researchers have developed a visual map showing the vitamin D status of Dublin’s inhabitants. It shows considerable variations in vitamin D deficiency among people living in certain geographic and urban locations within the greater Dublin region – some areas show five times higher rates of deficiency than others.

The publication of the research coincides with international Vitamin D awareness day — 2nd November — which recognises vitamin D deficiency as a world problem.

The research, carried out by Trinity College Dublin and St James’s Hospital uses a combination of geo mapping and traditional research involving over 5,200 individuals to accurately show the first very detailed picture of variations in vitamin D status in a large urban centre.

The key findings include:

• 1 in 8 (12.5%) of the population of greater Dublin was found to be vitamin D-deficient, with overall vitamin D deficiency during winter at 15.2% and overall vitamin D deficiency during summer at 10.8%. The overall rate is similar to that found in a large recent study of European adults.
• However, the most socio-economically deprived and ethnically diverse urban locations (Dublin 8 and Lucan postal districts) had the highest rates of deficiency with one in four people (25%) on average vitamin D-deficient. This is double the rate for the Dublin region as a whole and up to five times higher than in other specific areas.
• In comparison, in Dublin 16 in summer, the deficiency rate was only 5% and in winter, the deficiency rate in Kildare was 7.6%.
• Females had significantly higher levels of vitamin D concentration than males — 25% higher on average.
• Younger people (between 18 and 50 years of age) had considerably lower vitamin D levels than those over 50 — 27% lower in winter and 20.7% lower in summer than the over 50s. This is contrary to a popular perception that vitamin D is a greater problem for older adults and the elderly.

The picture painted by these detailed findings is that those who live in more economically deprived areas, as well as men and younger people, have significantly lower concentrations of vitamin D compared with women, older adults and those living in more affluent areas.

The advantage of using this kind of visual geo mapping is that the data can be used to aid  the rapid identification of vitamin D status trends within a major urban area, which can pick up very specific regional factors that can be missed in large surveys.

Also, the researchers commented that urban areas have their own unique economic, social and climatic micro-environments compared to the wider country as a whole, so investigating a city-wide vitamin D status can provide a unique and valuable snap shot of how vitamin D concentrations are affected by the demands of urban residence.

Author of the study and Research Fellow at the Centre for Medical Gerontology, Trinity, Dr Eamon Laird said: “This is the first time that a geographical map of the greater Dublin region or any urban region in Ireland has been developed. Our findings provide useful data to help inform public health policy regarding endemic vitamin D insufficiency to help target the population groups and resident location areas most at risk.”

Commenting on the possible reasons for the differences between certain areas within the greater Dublin region, Dr Laird said: “Other studies have shown an association between social deprivation and lower vitamin D, possibly due to diet as vitamin D-rich foods such as oily fish or fortified foods tend to be more expensive. Also, these locations in Dublin are more ethnically diverse compared to other areas, with higher numbers of non-Caucasians. Increased skin pigmentation plus ethnic lifestyle choices such as traditional clothing and/or dietary habits can also increase the risk of deficiency.”

Vitamin D has for a long time been associated with musculoskeletal and bone health conditions such as rheumatoid arthritis and osteoporosis. However, more recently, doctors believe that vitamin D deficiency is a risk factor in a greater range of serious health conditions such as heart disease, type 2 diabetes, cancer and inflammatory conditions.

In humans the primary source of vitamin D is ultraviolet (UV)-B radiation from the sun; however, this is highly dependent on a range of limiting factors such as cloud cover, sun-screen use, age, BMI, season and latitude.

The paper is available here.