Optimal vitamin D and sunbed use
In this commentary Professor Emeritus Brian Diffey shows that he, in contrast to many other scientists, has an open eye for the natural and most efficient way of improving vitamin D status, the skin. Exposure to UV light - including the use of sunbeds....
Sunlight or diet: what is the answer for providing sufficient vitamin D
Macdonald and colleagues make an important point about the poorly understood contribution of tissue stores of vitamin D to overall 25-hydroxyvitamin D [25(OH)D] status, a view with which I agree and alluded to in my paper.1 As
shown by Macdonald et al. in their Figure, and supported by the data in Table 3 of my paper,1 winter-time levels of circulating 25(OH)D in the U.K. are typically around 40 nmol L)1, rising to 60 nmol L)1 in the summer.
These summer values are the result of spending a few hours per day outside. For example, in the study reported by Hyppo¨- nen and Power,2 who measured serum 25(OH)D concentrations in over 7000 white British people aged 45 years and found a mean summer to winter difference of 19Æ2 nmol L)1, the authors reported that during the summer just 5Æ5% of respondents claimed to spend < 30 min per day outdoors, with 42Æ1% spending between 0Æ5 and 3 h and 52Æ4% spending 3 h or more outdoors per day.
These times outdoors are similar to those observed in a Danish study3 where during a summer season a mean of 2Æ9 h (range 0Æ3-6Æ5) per day was spent outdoors.
Clearly the vast majority of people spends much longer outdoors than the ubiquitous advice that 10-20 min of daily casual sun exposure during the summer months is adequate in maintaining a healthy vitamin D status.4 I argued in my paper1 that to increase summer-time levels above 60 nmol L)1 would require a degree of sun exposure that could compromise skin health and suggested that it might be safer and more effective to fortify more foods with vitamin D and ⁄or to consider the use of supplements during the winter months.
Macdonald et al. are, of course, correct that this route is not without its drawbacks and problems and so it seems that maintaining ‘adequate' levels of vitamin D throughout the year, either through summer sun exposure or diet ⁄supplements, remains a challenge.
For those who believe that current serum levels of 25(OH)D (vitamin D) are inadequate during the winter, the most effective approach in addressing this deficiency could be through exposure to artificial UVB radiation. i.e use a sunbed! 5,6
Brian L Diffy - Professor Emeritus
Dermatological Sciences, University of Newcastle, B.L. DI F F E Y
Newcastle upon Tyne NE2 4HH, U.K.
1 Diffey BL. Modelling the seasonal variation of vitamin D due to
sun exposure. Br J Dermatol 2010; 162:1342-8.
2 Hyppo¨nen E, Power C. Hypovitaminosis D in British adults at age
45 y: nationwide cohort study of dietary and lifestyle predictors.
Am J Clin Nutr 2007; 85:860-8.
3 Thieden E, Philipsen PA, Heydenreich J, Wulf HC. Vitamin D level
in summer and winter related to measured UVR exposure and
behaviour. Photochem Photobiol 2009; 85:1480-4.
4 Diffey BL. Is casual exposure to summer sunlight effective at maintaining
adequate vitamin D status? Photodermatol Photoimmunol Photomed.
5 Rhodes LE, Webb AR, Fraser HI, Kift R, Durkin MT, Allan D,
O'Brien SJ, Vail A, Berry JL. Recommended summer sunlight exposure
levels can produce sufficient (‡20 ng ml)1) but not the proposed
optimal (‡32 ng ml)1) 25(OH)D levels at UK latitudes. J
Invest Dermatol 2010; 130:1411-1418.
6 Moan J, Lagunova Z, Cicarma E, Aksnes L, Dahlback A, Grant WB,
Porojnicu AC. Sunbeds as Vitamin D Sources. Photochem Photobiol
Key words: diet, sunlight, vitamin D
Conflicts of interest: none declared.
_ 2010 The Authors
Journal Compilation _ 2010 British Association of Dermatologists • British Journal of Dermatology 2010 163, pp424-437