Unlike vitamin D3, which is made by the action of UVB sunlight on the skin and also obtained in the diet, vitamin D2 only comes from dietary sources( Reference Cashman, Kinsella and McNulty 1 ). The few items in the human food chain that contain significant amounts of vitamin D2 are supplements, fortified foods, ultraviolet B (UVB) light exposed mushrooms, and food made with UVB exposed bakers’ yeast. Despite the widely held assumption that dietary exposure to vitamin D2 is limited, we have recently reported that 78 % (n = 884) of participants in the National Adult Nutrition Survey (NANS) in Ireland had serum 25-hydroxyvitamin D2 (25(OH)D2) concentrations above the limit of quantification( Reference Cashman, Kinsella and McNulty 1 ). Data on serum 25(OH)D2 in other European populations is lacking. The objective of this study was to generate serum 25(OH)D2 data and estimates of vitamin D2 intakes using subsets of serum samples from 14 European population studies.
Bio-banked sera (each n = 100–170) from Ireland [adults, children], Germany [adults, children and adolescents], Norway [adolescents, adults], Netherlands [adults, older adults], Finland [ethnic minority adults], Iceland [older adults], Denmark [children] and multi-country [adolescents] were analysed as part of the European Commission-funded ODIN project (www.odin-vitd.eu/) using our liquid chromatography tandem mass spectrometry method which measures 25-hydroxyvitamin D3 and 25(OH)D2 simultaneously( Reference Cashman, Kinsella and McNulty 1 ). Data from 9 randomized controlled trials which tested the efficacy of UVB-exposed mushroom products or vitamin D2-enhanced beverages in improving vitamin D status( Reference Cashman, Kiely, Seamans and Urbain 2 , Reference Biancuzzo, Young and Bibuld 3 , Reference Fisk, Theobald and Sanders 4 ), showed a mean response in serum 25(OH)D2 (nmol/L) to ingested vitamin D2 (μg) of 0·95 nmol/L per μg/day. This response factor was used to estimate median intakes in each of the 14 populations.
1Estimates are presented as the average (SD) of medians from the individual population studies within a country where there were two studies.
*Value above the limit of detection (0·44 nmol/L) but below limit of quantitation (1·43 nmol/L).
Median concentrations of serum 25(OH)D2 ranged from 0·8–2·5 nmol/L in these European populations, while median vitamin D2 intakes were estimated to be in the range 0·9–2·6 µg/day (see table), with Ireland having the highest estimated median intake of 2·6 µg/day. In conclusion, based on serum 25(OH)D2 concentration data, European populations have exposure to vitamin D2 in their diet. The exact dietary sources of vitamin D2 in the European food chain needs to be investigated.