Large variations in vitamin D levels depending on Dublin postcode

Posted on: 09 September 2020

Researchers from the Mercer’s Institute for Successful Ageing (MISA) at Trinity College have shown that vitamin D deficiency is widespread across Dublin and surrounding areas in one of the largest studies ever carried out in Europe. The research examined blood levels of vitamin D from 36,466 patients over a five year period (2014 – 2018) and found that 1 in 6 were deficient, rising to 1 in 4 in the winter.

The findings have been published in the journal ‘Nutrients’.

Vitamin D is important as it contributes to the maintenance of bone and muscle health and helps support a healthy immune system. Using a tool known as geo-mapping, the researchers were able to create a visual map of vitamin D levels across Dublin and East Leinster. Researchers identified large variations in vitamin D status between adults of different ages and locations. The study found that vitamin D deficiency is a problem for everyone as surprisingly, the youngest participants in the cohort (18-39 yrs category) had the lowest vitamin D levels as did those in the ‘older’ category (80+ yrs). It also found that in general men had much lower levels than women. Some areas such as South Dublin and North Kildare showed lower levels of vitamin D deficiency compared to North Dublin and West Dublin and there were also big differences between postcodes of close proximity.The prevalence of deficiency was also high in participants located in some counties within and outside Leinster.

Key findings: 

  1. 1 in 6 Irish adults in the Dublin population and surrounds (including some counties within and outside Leinster) are vitamin D deficient rising to one in four in the Winter indicating a large proportion have inadequate vitamin D status.
  2. Young adults (18-39 yrs) were most likely to be vitamin D deficient as were those aged 80+ yrs.
  3. Vitamin D deficiency was more common in men.
  4. Vitamin D levels were lowest in the winter, with those living in inner city Dublin and West Dublin having the highest rates of deficiency year round.
  5. While there were more vitamin D tests requested over the five year period, there was no improvement in vitamin D levels in the population.

Helena Scully, Research Fellow at the School of Medicine and first author on the study said:

This study found lower levels of vitamin D in Irish adults than in the previous population based NANS study suggesting that vitamin D deficiency is more of an issue than once thought.It’s important that the public is aware of the need to also get vitamin D through the diet and/or supplements especially in the winter. Ensuring adequate levels of vitamin D in your diet can support bone health and normal function of your immune system. It’s also important in young adults where peak bone density isn’t reached until about the mid 20’s. Eating a balanced diet and including dietary sources of vitamin D such as oily fish like salmon and mackerel and also fortified foods such as cereals and fortified milk is important.

Dr Eamon Laird, Senior Research Fellow at the School of Medicine, Trinity College Dublin said:

Yet again we see more widespread vitamin D deficiency in our population with men, younger adults and the less affluent areas worst affected. This shows vitamin D deficiency is not just an ‘older adult’ problem.Rates of deficiency have not improved therefore education to our identified at risk groups (who are often forgotten) around the importance of vitamin D in the diet is crucial.

The paper is available in the journal ‘Nutrients’ here: