The role of sunlight exposure in determining the vitamin D status of the U.K. white adult population

Authors

  • A.R. Webb,

    1. School of Earth Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, U.K.
    Search for more papers by this author
  • R. Kift,

    1. School of Earth Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, U.K.
    Search for more papers by this author
  • M.T. Durkin,

    1. Photobiology Unit, Dermatological Sciences, Epithelial Sciences Research Group, School of Translational Medicine, University of Manchester, Manchester Academic Health Science Centre, Salford Royal NHS Foundation Hospital, Salford, U.K.
    Search for more papers by this author
  • S.J. O’Brien,

    1. Occupational and Environmental Health Research Group, School of Translational Medicine, University of Manchester, Manchester Academic Health Science Centre, Salford Royal NHS Foundation Hospital, Salford, U.K.
    Search for more papers by this author
  • A. Vail,

    1. Health Methodology Research Group, School of Community Based Medicine, University of Manchester, Manchester Academic Health Science Centre, Manchester, U.K.
    Search for more papers by this author
  • J.L. Berry,

    1. Vitamin D Research Laboratory, Endocrine Sciences Research Group, School of Biomedical Sciences, University of Manchester, Manchester Academic Health Science Centre, Manchester Royal Infirmary, Manchester, U.K.
    Search for more papers by this author
  • L.E. Rhodes

    1. Photobiology Unit, Dermatological Sciences, Epithelial Sciences Research Group, School of Translational Medicine, University of Manchester, Manchester Academic Health Science Centre, Salford Royal NHS Foundation Hospital, Salford, U.K.
    Search for more papers by this author

  • Conflicts of interest
    None declared.

Ann Webb.
E-mail: ann.webb@manchester.ac.uk

Summary

Background  Vitamin D is necessary for bone health and is potentially protective against a range of malignancies. Opinions are divided on whether the proposed optimal circulating 25-hydroxyvitamin D [25(OH)D] level (≥ 32 ng mL−1) is an appropriate and feasible target at population level.

Objectives  We examined whether personal sunlight exposure levels can provide vitamin D sufficient (≥ 20 ng mL−1) and optimal status in the U.K. public.

Methods  This prospective cohort study measured circulating 25(OH)D monthly for 12 months in 125 white adults aged 20–60 years in Greater Manchester. Dietary vitamin D and personal ultraviolet radiation (UVR) exposure were assessed over 1–2 weeks in each season. The primary analysis determined the post-summer peak 25(OH)D required to maintain sufficiency in wintertime.

Results  Dietary vitamin D remained low in all seasons (median 3·27 μg daily, range 2·76–4·15) while personal UVR exposure levels were high in spring and summer, low in autumn and negligible in winter. Mean 25(OH)D levels were highest in September [28·4 ng mL−1; 28% optimal, zero deficient (<5 ng mL−1)], and lowest in February (18·3 ng mL−1; 7% optimal, 5% deficient). A February 25(OH)D level of 20 ng mL−1 was achieved following a mean (95% confidence interval) late summer level of 30·4 (25·6–35·2) and 34·9 (27·9–41·9) ng mL−1 in women and men, respectively, with 62% of variance explained by gender and September levels.

Conclusions  Late summer 25(OH)D levels approximating the optimal range are required to retain sufficiency throughout the U.K. winter. Currently the majority of the population fails to reach this post-summer level and becomes vitamin D insufficient during the winter.

Ancillary