The recent spell of warm and sunny weather we’ve had here in the UK (which came to an abrupt halt this week) has been welcomed by most. While the sun has perhaps made us feel better and given a glow to our skin, the downside is that at this time of year, the sun is too low in the sky to generate vitamin D in the skin.
This fact reminds me that a significant proportion of people in the UK have low vitamin D levels. Quite what constitutes ‘low’ depends on who you ask. I generally advise people to shoot for levels of around 50 ng/ml (125 nmol/l). Conventional cut-offs for ‘suboptimal’ and ‘low’ levels are considerably lower than this.
One potential symptom of vitamin D deficiency is pain. In a previous post I highlighted this problem, and its particular relevance to those with dark skin living in places that don’t necessarily get much sunlight. Dark-skinned individuals are at particular risk because, for a given amount of sunlight, they usually make less vitamin D compared to fair-skinned individuals.
The fact that skin colour determines, to some degree, how much vitamin D we make and what our vitamin D levels will ultimately be can cause us to think that fair-skinned individuals are somehow protected from vitamin D deficiency. However, a new study suggests that this is far from the case.
In this UK study, data was collected from individuals regarding things like sun exposure, vitamin D supplement use, and vitamin D levels . Much of the data came from individuals with a history of malignant melanoma, and comparisons were made with individuals free from this disease (controls).
One key finding of this study is that fair-skinned ‘sun sensitive’ individuals had, overall, lower vitamin D levels compared to individuals not deemed to be sun sensitive. What is more, to achieve levels of 24 ng/ml (60 nmol/l) sun sensitive individuals required supplementation in addition to whatever sun exposure they got.
In short, fair-skinned individuals are at risk of vitamin D deficiency. The likely explanation?
Their propensity to burning (and perhaps some anti-sun propaganda thrown in) means that they simply don’t get enough sunlight to generate anything like optimal levels of vitamin D. Fair-skinned individuals should most certainly not be excluded from vitamin D testing, and supplementation should at least be considered for those who show low levels.
There were other interesting things that came out of this study that did not make it into the press. It was found, for instance, that when individuals who were diagnosed with melanoma, they tended to have lower vitamin D levels compared to individuals without the disease. This finding is consistent with evidence that links lower vitamin D levels with increased risk of certain cancers (notably those of the prostate, breast and colon). The authors of the study also refer to evidence which links low vitamin D levels to thicker melanomas, and worse outcomes from this disease.
The authors also draw our attention to the fact that while sunburn appears to be a risk factor for melanoma, occupational exposure is actually associated with a reduced risk of melanoma (outdoor workers are generally at reduced risk compared to indoor workers, for instance). The authors also cite previous evidence of their own linking weekend sun exposure with reduced melanoma risk. See here for a previous post where I highlight a cancer specialist’s call for us to get more sun.
1. Davies JR, et al. The determinants of serum vitamin D levels in participants in a melanoma case-control study living in a temperate climate. Cancer Causes Control. 2011;22(10):1471-82