Inequities in advice on vitamin D?

Abstract

Vitamin D refers to precursors of the active secosteroid hormone 1,25-dihydroxyvitamin D3 (calcitriol). Vitamin D is available from two sources: skin exposure to ultraviolet B radiation (UV) and diet.1 UV photolyses 7-dehydrocholesterol in the skin to pre-vitamin D3, which then isomerizes to vitamin D3. Vitamin D is available from some fortified foods (e.g. cereals and margarine), oily fish (e.g. salmon), eggs and vitamin supplements.1 Relative to sun exposure, diet is a poor source of vitamin D in the UK, providing only between 80 and 120 IU/day, whereas skin UV exposure for 20 min in a light-skinned person during the summer months will produce upwards of 10 000 IU of vitamin D.1,2 However, increased skin pigmentation and factors that reduce the strength of UV reaching the Earth’s surface (e.g. winter season, high latitude, pollution and cloud cover), all contribute to reduce skin vitamin D production3 to the point that diet may become the primary source. The UK Food Standards Agency’s current guidelines on vitamin D supplementation4 suggest that individuals who are of Asian origin, who cover up their skin while outside, rarely get outdoors or who eat no meat or oily fish ‘might want to think about’ taking vitamin D. However, this guidance omits one very important group who would derive possibly the most benefit from vitamin D …