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    What is vitamin D ?

    Vitamin D is a fat-soluble vitamin, which plays a central role in our health. It is obtained during exposure to sunlight by skin biosynthesis and from natural dietary sources. Due to the lack of prolonged sunshine in Ireland, our position in northern Europe and the low dietary vitamin D intake, deficiency is a critical problem in Ireland for all age groups1.

    The dietary guideline in Ireland for infants is 5µg/day and the healthy eating guidelines are currently being updated for adults2. The Scientific Advisory Committee on Nutrition (SACN) have published recommendations that the Recommended Nutrient Intake (RNI) for those aged 4 and above is 10 µg/day3.

    What is it used for in our body?

    The functions of vitamin D include:

    • bone health by regulating calcium and phosphorus metabolism4
    • supporting immunity through helping to maintain and strengthen the body's defense against infection14
    • supporting healthy muscles 4.

    Research has also shown that those with low levels of vitamin D have an an increased risk of 4, 5:

    • type 1 diabetes mellitus
    • cardiovascular disease
    • neurological disease
    • autoimmune disease and some cancers.

    The direct and indirect medical costs of which, have been estimated in Europe to be in the hundreds of billions of euros6.

    Evidence is also emerging, linking vitamin D deficiency with the severity of Covid-19 disease infection, which is a concern considering the global pandemic.

    Vitamin D deficiency in Irish adults and children

    Vitamin D levels in the body are measured via Serum 25-dihydroxyvitamin D (25(OH)D). It is generally agreed by expert groups, that Vitamin D deficiency falls within 25(OH)D concentrations of <25 or <30nmol/L 12.

    Deficiency has the potential for far reaching implications in health and chronic disease prevention. Some believe that the level of deficiency within Europe is at a crisis level, where 13% of those sampled had a deficiency. Data for the US population was reported at 5.9% and the Canadians at 7.4% 7. This data was based on whole-population estimates, which includes variance by age, where levels can be lower in childhood and older adults 8.

    Research of the Irish population, show varying degrees of deficiency:

    • Adults showed deficiency rates of 6.7% in summer and 11.1% in winter9.
    • 93% of children had an intake below the 10 µg/day recommendation10,11
    • 3% of adolescents are deficient in vitamin D13.

    Boosting your vitamin D intake

    Based on these levels of deficiency, dietary intake information, the geographical position of Ireland and low ultraviolet UVB exposure throughout year, the following are other ways to boost your vitamin D.


    • Through foods rich in vitamin D like animal products including oily fish, eggs, liver and red meat and mushrooms.
    • Through fortified foods like milk, breakfast cereals and some breads. However, be mindful when choosing some breakfast cereals and read the labels for the sugar content.


    • Taking a daily vitamin D supplement is another way of getting vitamin D especially through the winter months, though food first is always recommended. Its important not to take more than recommended, without consulting with your GP first.
    References: 1. Hill et al., Vitamin D intakes in 18–64-y-old Irish adults, EJCN, 2004. 2.Vitamin D and Your Baby -, 2019. 3 SACN recommendations on vitamin D, 2016. 4 Hossein-nezhad et al,. Vitamin D for Health: A Global Perspective. Mayo Clinic Proceedings. 2013. 5 McCarroll et al., Determinants of 25-hydroxyvitamin D in older Irish adults. Age and Ageing, 2015. 6 Calvo et al., Vitamin D research and public health nutrition: a current perspective, PHN, 2017. 7 Cashman et al., Vitamin D deficiency in Europe: pandemic? AJCN, 2016 .8 Cashman K. Vitamin D Deficiency: Defining, Prevalence, Causes, and Strategies of Addressing. Calcified Tissue International, 2019. 9 Cashman et al., Vitamin D status of Irish adults: findings from the National Adult Nutrition Survey, BJN 2012. 10 Hennessy et al., The role of fortified foods and nutritional supplements in increasing vitamin D intake in Irish preschool children, EJN 2016. 11 IUNA Summary Report on: Food and Nutrient Intakes, Body Weight, Physical Activity and Eating Behaviours in Children Aged 5-12 Years in Ireland, 2019. 12 Cashman et al., Contribution of nutrition science to the vitamin D field—Clarity or confusion?. The Journal of Steroid Biochemistry and Molecular Biology, 2018. 13 Hill et al., Vitamin D status and its determinants in adolescents from the Northern Ireland Young Hearts 2000 cohort, BJN 2008. 14 Wu et al., Nutritional Modulation of Immune Function: Analysis of Evidence, Mechanisms, and Clinical Relevance. Frontiers in Immunology, 2019.