Indian and Pakistani immigrants have the same capacity as Caucasians to produce vitamin D in response to ultraviolet irradiation.

To investigate whether the high prevalence of osteomalacia and rickets among Indian and Pakistani immigrants to Great Britain is due to impaired capacity to produce vitamin D3 in their skin, the serum vitamin D concentrations of six Asians in response to 1.5 times their minimal erythemal dose (MED) of whole-body ultraviolet radiation (UVR) was studied. The mean serum vitamin D concentrations rose from a baseline of 2 +/- 2 ng/ml before exposure to UVR to a peak of 38 +/- 12 ng/ml at 24 h, gradually declining back to baseline by day 9. This response was not significantly different from that seen in Caucasian controls. The UVR needed to produce an MED in Asians, with their darker skin, was greater (49-133 mJ/cm2) than that required in Caucasians (31-48 mJ/cm2). Asians may need longer exposure to sunlight than Caucasians do to give a similar response, but the capacity to produce vitamin D is no different in Asian than in Caucasian skin.