Vitamin D Deficiency in Ireland: Who's at Risk and How Much You Need

Ireland sits between about 51 and 55 degrees north. At that latitude, from roughly October to March, the sun is too low for the skin to make meaningful amounts of vitamin D, no matter how long you spend outdoors. Add cloud, indoor jobs and a diet with few natural vitamin D sources, and it's no surprise that low vitamin D is common here, especially in winter.

This guide covers what the Irish research shows, who is most at risk, how much vitamin D the official advice recommends, and how to supplement sensibly.

What vitamin D does

Vitamin D contributes to the normal absorption and utilisation of calcium and phosphorus, the maintenance of normal bones, teeth and muscle function, and the normal function of the immune system.

Unlike most vitamins, the main source for most people is not food but sunlight on the skin. That's why where you live and the time of year make such a difference.

What the Irish research shows

• The Irish Longitudinal Study on Ageing (TILDA) at Trinity College Dublin found that about one in eight adults over 50 were vitamin D deficient (below 30 nmol/L). In winter, that rose to about one in four.
• Research from University College Cork found that among Irish women aged 23 to 50, vitamin D insufficiency was around 35% in winter compared with 4% in summer.
• National nutrition surveys have repeatedly found that average vitamin D intakes from food in Irish adults fall well below recommended amounts.

The exact percentage depends on the age group, the season and which cut-off is used, but the pattern is consistent: winter is when levels drop, and a significant share of people fall short.

Who is most at risk

• Adults aged 65 and over, whose skin makes vitamin D less efficiently
• People who spend little time outdoors, including those who are housebound or in residential care
• People with darker skin, which needs more sun exposure to make the same amount of vitamin D
• People who cover most of their skin outdoors
• People living with obesity, as vitamin D is stored in body fat
• Pregnant and breastfeeding women, and babies
• People with conditions that affect fat absorption, such as coeliac disease or Crohn's disease

How much vitamin D is recommended?

• Adults 65 and over (Ireland): the Department of Health advises a daily vitamin D3 supplement of 15 micrograms (600 IU) all year round.
• Babies (Ireland): the HSE advises 5 micrograms of vitamin D3 daily for babies from birth to 12 months.
• Everyone in the UK: the NHS advises considering 10 micrograms (400 IU) daily during autumn and winter.
• Upper safe limit: EFSA sets 100 micrograms (4,000 IU) a day from all sources for adults.

Many adults in Ireland choose a supplement of 10 to 50 micrograms a day through the darker months. If you'd like to know your own level, your GP can test 25-hydroxyvitamin D. Results are usually reported in nmol/L: below 30 is generally regarded as deficient, and 50 or above as adequate for bone health.

Food sources

Few foods are naturally rich in vitamin D. The best are oily fish (salmon, mackerel, sardines, herring), egg yolks and, in smaller amounts, red meat and liver. Fortified foods, such as some milks, breakfast cereals and spreads, add to intake. Mushrooms exposed to UV light contain vitamin D2. Even a good diet rarely provides enough in winter, which is why supplements are widely recommended.

D3 vs D2

D3 (cholecalciferol) is the form the skin makes and is generally more effective at raising and maintaining blood levels than D2 (ergocalciferol). Most supplements use D3. Vegan D3 made from lichen is available.

Tips for supplementing

• Take it with a meal that contains some fat; vitamin D is fat-soluble.
• Be consistent. Daily intake builds and maintains levels over weeks.
• Add it all up. Count multivitamins, fish oils with added vitamin D, and fortified foods so you stay under the upper limit.
• Consider K2 alongside it. Vitamin K contributes to the maintenance of normal bones. See our guide to taking vitamin D3 with K2.
• Check with your GP if you have kidney disease, high calcium, sarcoidosis, take prescribed medicines, or before taking K2 if you're on warfarin.

Key takeaways

• At Ireland's latitude, the skin makes little or no vitamin D from about October to March.
• Irish studies show deficiency is common, and roughly doubles in winter among older adults.
• The Department of Health advises 15 micrograms daily for everyone 65 and over; babies need 5 micrograms daily.
• Stay under 100 micrograms (4,000 IU) a day from all sources.
• A GP blood test is the only way to know your own level.

Our NeuroThrive™ D3 + K2 provides 50 micrograms (2,000 IU) of vitamin D3 with 75 micrograms of K2 (MK-7) per tablet.

Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. This article is for general information and is not medical advice.