Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited

Objectives. Sunlight exposure of the skin is known to be the most important source of vitamin D. The aims of this study were: (i) to estimate vitamin D status amongst sunlight-deprived individuals (veiled Arab women, veiled e thnic Danish Moslem women and Danish controls); and (ii) through food intak e analysis to estimate the oral intake of vitamin D necessary to keep a nor mal vitamin D status in sunlight-deprived individuals. Design. Cross-sectional study amongst randomly selected Moslem women of Ara b origin living in Denmark. Age-matched Danish women were included as contr ols. To control for racial differences, a group of veiled ethnic Danish Mos lem women (all Caucasians) was included. Setting. Primary Health Care Centre, City Vest and Department of Endocrinol ogy and Metabolism C, University Hospital of Aarhus, Aarhus Amtssygehus, Aa rhus, Denmark. Subjects. Sixty-nine Arab women (60 veiled, nine non-veiled) and 44 age-mat ched Danish controls were randomly selected amongst patients contacting the primary health care centre for reasons other than vitamin D deficiency. Te n ethnic Danish Moslem women were included through a direct contact with th eir community. Main outcome measures. Serum levels of 25-hydroxyvitamin D were used as est imates of vitamin D status. Intact parathyroid hormone (PTH) was used to co ntrol for secondary hyperparathyroidism. Alkaline phosphatase and bone-spec ific alkaline phosphatase were used as markers for osteomalacic bone involv ement. Oral intake of vitamin D and calcium were estimated through a histor ical food intake interview performed by a trained clinical dietician. Results. Veiled Arab women displayed extremely low values of 25-hydroxyvita min D: 7.1 +/- 1.1 nmol L-1, compared with 17.5 +/- 2.3 (P < 0.002) in ethn ic Danish Moslems and 47.1 +/- 4.6 (P < 10(-17)) in Danish controls. PTH wa s increased amongst veiled Arab women: 15.6 +/- 1.8 pmol L-1, compared with 5.7 +/- 1.4 in ethnic Danish Moslems and 2.7 +/- 0.3 (P < 10(-6)) in Danis h controls. The vitamin D intake (including food supplementation) was very low amongst Arab women: 1.04 mu g day(-1), compared with 13.53 amongst ethn ic Danish Moslems and 7.49 amongst Danish controls (P < 0.0005). Conclusions. Severe vitamin D deficiency is prevalent amongst sunlight-depr ived individuals living in Denmark. In veiled Arab women, vitamin D deficie ncy is the result of a combination of limitations in sunlight exposure and a low oral intake of vitamin D. The oral intake of vitamin D amongst veiled ethnic Danish Moslems was, however, very high, at 13.53 mu g (approximatel y 600 IU), but they were still vitamin D-deficient. Our results suggest tha t the daily oral intake of vitamin D in sunlight-deprived individuals shoul d exceed 600 IU; most probably it should be 1000 IU day(-1) to secure a nor mal level of 25-hydroxyvitamin D. This finding is in contrast with the comm only used RDA (recommended daily allowance) for adults in Europe: 200 IU da y(-1).