Diet, environmental factors, and lifestyle underlie the high prevalence of vitamin D deficiency in healthy adults in Scotland, and supplementation reduces the proportion that are severely deficient

Vitamin D deficiency has recently been implicated as a possible risk factor in the etiology of numerous diseases, including nonskeletal conditions. In humans, skin synthesis following exposure to UVB is a potent source of vitamin D, but in regions with lowUVB, individuals are at risk of vitaminDdeficiency.Our objectiveswere to describe the prevalence of vitaminDdeficiency and to investigate determinants of plasma 25-hydroxyvitamin D (25-OHD) concentrations in a high northern latitude country. Detailed dietary, lifestyle, and demographic data were collected for 2235 healthy adults (21-82 y) from Scotland. Plasma 25-OHD was measuredby liquid chromatography-tandemMS.Amongstudy participants,34.5%were severely deficient (25-OHD<25nmol/L) and28.9%wereat highrisk of deficiency (25-40nmol/L). Only36.6%of participantswere at lowrisk of vitaminDdeficiencyor had adequate levels (>40 nmol/L). Among participants who were taking supplements, 21.3% had a May-standardized 25-OHD concentration (>50 nmol/L, 54.2% had 25-50 nmol/L, and 24.5% had (<25 nmol/L, whereas this was 15.6, 43.3, and 41%, respectively, among those who did not take supplements (P<0.0001). The most important sources of vitamin D were supplements and fish consumption. Vitamin D deficiency in Scotland is highly prevalent due to a combination of insufficient exposure to UVB and insufficient dietary intake. Higher dietary vitamin D intake modestly improved the plasma 25-OHD concentration (P = 0.02) and reduced the proportion of severely deficient individuals (P<0.0001). In regions with low UVB exposure, dietary and supplement intakemay bemuchmore important than previously thought and consideration should be given to increasing the current recommended dietary allowance of 0-10 mg/d for adults in Scotland.