The research could strengthen calls for higher levels of vitamin D fortification and supplementation as a growing number of studies report that significant sections of the population are not getting enough of the vitamin, and are putting themselves at higher risk of health problems later in life.
"Unfortunately, there are very few foods that are good sources of vitamin D, and those that are, such as oily fish, are not widely consumed so it is actually quite difficult to get vitamin D from food alone. For groups at risk of low vitamin D status it may be that supplements are needed," explained lead researcher Dr Julie Wallace from the University of Ulster.
Only recently researchers from the Britain reported that Asian children should be receiving vitamin D supplements amid fears of insufficient levels of the vitamin, and another study reported that over 70 per cent of seemingly healthy teenage girls might be vitamin D deficient, putting them at an increased risk of osteoporosis.
Vitamin D is produced in the skin on exposure to UVB radiation and can also be consumed in small amounts from the diet. UK researchers recently proposed 10 to 15 minutes of unprotected exposure to the midday sun as a good source of the vitamin. In the US, however, where over 1.5m people are diagnosed with skin cancer every year, experts are pushing supplements, and slamming sun exposure recommendations as "highly irresponsible".
Moreover, recent studies have shown that sunshine levels in some northern countries are so weak during the winter months that the body makes no vitamin D at all, leading some to estimate that over half of the population in such countries have insufficient or deficient levels of the vitamin.
"For six months of the year - roughly from the end of September until mid-March - we cannot make vitamin D through exposure to sunlight - even if we were out all day every day, because the sun is too low in the sky. Our summertime levels will last for part of the year, but by the end of winter we know from our own research that those stores are low," said Wallace.
"Traditionally the lack of Vitamin D was thought to be a problem for institutionalised elderly people who did not get exposure to sunlight, but more and more we are realising that it is a problem for the whole population."
The three-year project, funded by the Food Standards Agency, will also establish if there are differences in vitamin D levels between people living in Northern Ireland and those living in the sunnier southern climes of Cork.
To date, over 120 adults between the ages of 20 and 40 have been recruited and will be provided with vitamin D supplements from October to March to calculate how much vitamin D is needed from the diet to maintain the summer time levels. Next year the study will move on to the 65-plus age group.
"While in the current study we are focusing on these two groups, we believe vitamin D research is also required in other groups including children, adolescents and pregnant women," said Wallace.
Vitamin D deficiency can lead to a range of health problems, including rickets, poor tooth formation, convulsions, general ill health, and stunted growth. It has also been linked to an increased risk of certain cancers, cardiovascular disease, diabetes, and osteoporosis.
The best source could be from fortified foods and supplements.