Vitamin D is a very important component in human metabolism. Two sources exist for Vitamin D biosynthesis, either from exposure to sun light or from diet. The most well-known and important function of Vitamin D depends on its biological active form Calcitriol (1,25-(OH)2D3): regulating the circulating concentrations of calcium and phosphate, and promoting the growth and remodeling of bone.
The blood level of Vitamin D is strongly dependent on the exposure to sunlight. The local geographical latitude and various other factors (e.g. clouds absorb the essential UV radiation) affect this exposure. Further skin color, long working hours indoors and type of clothing are important. The diet intake of Vitamin D is generally low although in various countries specific food is fortified with Vitamin D.
Deficiencies in Vitamin D are seen in all sections of western populations. The consequences of these deficiencies are complex. At this point of time primarily the role Vitamin D in growth and remodeling of bone is seen as being affected by deficiencies resulting in an enhanced prevalence of fractures. There are however studies indicating associations between Vitamin D deficiency and cancers of colon, prostate, breast, and pancreas; autoimmune diseases, rheumatoid arthritis, Crohn’s disease, multiple sclerosis; infectious diseases; cardiovascular disease and all-cause mortality.
The Endocrine Society has defined Vitamin D deficiency as a serum level of 25(OH)D below 50 nmol/L, and Vitamin D insufficiency as a 25(OH)D blood level of 52.5–72.5 nmol/L. Taking these recommendations as starting point the prevalence of Vitamin D deficiency is very large at the end of the winter period in the countries above the 33rd degree latitude, with an even higher prevalence of individuals with Vitamin D insufficiency. This has led to advisory reports from national Health Councils from many western countries implicating that a section of the population needs Vitamin D supplementation. Studies have however shown unfortunately that these recommendations have limited effect on the Vitamin D blood levels in the population.
Assessment of Vitamin D blood level with the easy and friendly DBS method makes it possible to follow the effectivity of Vitamin D supplementation. The method is very helpful in studies with infants, elderly and obese individuals. Next to 25(OH)D3, DBSL offers also the assessment of 3-epi-25(OH)D3, especially for studies with children and elderly. The use of DBS can also help to enhance awareness of Vitamin D deficiency and of the efficacy of Vitamin D supplementation.