Recommended summer sunlight exposure amounts fail to produce sufficient vitamin D status in UK adults of South Asian origin

Am J Clin Nutr. 2011 Nov;94(5):1219-24. doi: 10.3945/ajcn.111.019976. Epub 2011 Sep 14.


Background: The cutaneous synthesis of vitamin D is dependent on UVB from sunlight, but melanin reduces the penetration of UVB and thus contributes to vitamin D insufficiency in individuals with darker skin. The national guidance provided on amounts of sunlight exposure in the United Kingdom is for the light-skinned population, and in the absence of dedicated information, darker-skinned people may attempt to follow this guidance.

Objectives: We determined the relative effect of a simulation of UK recommendations of summer sunlight exposure on the vitamin D status of individuals of South Asian ethnicity compared with that of whites.

Design: In a prospective cohort study, simulated summer sunlight exposures were provided under rigorous dosimetric conditions to 15 adults (aged 20-60 y) of South Asian ethnicity, and serum 25-hydroxyvitamin D [25(OH)D] was measured weekly. Dietary vitamin D intake was estimated. Outcomes were compared with those of 109 whites (aged 20-60 y) treated with the identical UV-radiation exposure protocol.

Results: At baseline (winter trough), all South Asians were vitamin D-insufficient [25(OH)D concentrations <20 ng/mL], and 27% of South Asians were vitamin D-deficient [25(OH)D concentrations <5 ng/mL]; although 25(OH)D concentrations increased postcourse (P < 0.0001), all South Asians remained vitamin D-insufficient. The mean increase in 25(OH)D was 4.3 compared with 10.5 ng/mL in the South Asian and white groups, respectively (P < 0.0001), and 90% of the white group reached vitamin D sufficiency postcourse. The median dietary vitamin D intake was very low in both groups.

Conclusions: Sunlight-exposure recommendations are inappropriate for individuals of South Asian ethnicity who live at the UK latitude. More guidance is required to meet the vitamin D requirements of this sector of the population. This study was registered at as ISRCTN 07565297.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Asia / ethnology
  • Cohort Studies
  • Female
  • Humans
  • Male
  • Middle Aged
  • Parathyroid Hormone / blood
  • Prospective Studies
  • Seasons
  • Sunlight*
  • United Kingdom
  • Vitamin D / analogs & derivatives*
  • Vitamin D / biosynthesis*
  • Vitamin D / blood
  • Young Adult


  • Parathyroid Hormone
  • Vitamin D
  • 25-hydroxyvitamin D

Associated data

  • ISRCTN/ISRCTN07565297