Fair-skinned individuals at risk of vitamin D deficiency

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 [1]. 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.

References:

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

5 Responses to Fair-skinned individuals at risk of vitamin D deficiency

  1. Chris 6 October 2011 at 3:16 pm #

    Does this direct us to think that intermittent recreational ‘overexposure’ could be more of a risk factor for melanoma than is a frequent and habituated kind of exposure? And does frequent habituated exposure condition the skin and raise vitamin D status in a way that is, perhaps, partly protective against burning, melanoma, and/or other cancerous conditions?

    We might be told that UV in sunlight can lead to skin cancer but as important is the manner in which we get our dose of sun and the way we condition our skin to its’ effects. Subject to how we elect to get our dose of sunlight might determine whether the dose increases risks or reduces them. Building a tan by increment promotes a tolerance factor, I suppose.

    That the cautionary message regarding potential harmful effects of the sun may have triumphed over a more objective and balanced view could have something to do with the value of the market for sales of sunscreens, I don’t doubt.

    The sun has to be respected. Fair skinned persons who live much of their lives indoors clearly have to treat the sun with respect, but mindful habituation, conditioning, and tanning – without burning – could be beneficial. Fewer colds and sniffles could be one benefit.

  2. Margaret Wilde 6 October 2011 at 4:35 pm #

    When I fell and suffered a bad fracture of the right humerus in 2007 it must certainly have been connected to bones weakened by vitamin D deficiency. I have always been sun sensitive and additionally had been advised by TB specialists to avoid the sun in case it re-awakened the TB I had for years in childhood and adolescence. But that deficiency of vitamin D must have been greatly exacerbated by the HRT I was inappropriately prescribed for years. See http://medicalxpress.com/news/2011-09-oral-steroids-linked-severe-vitamin.html

    And yet, until I started to read your blog, Dr Briffa, and had also read Dr Oliver Gillie’s long article about ‘the sunshine vitamin’, I had never heard from any doctor’s lips anything but dire warnings about vitamin D and the dangers of overdosing on it!

  3. jgkarob 7 October 2011 at 12:53 pm #

    Hi Dr Briffa,
    I have Multiple Sclerosis and along with many other net-savvy people with MS, I take two 5000 iu capsules of Vitamin D3 per day.
    I also have metabolic syndrome and since I started the D3 supplements, my fasting blood glucose levels and triglycerides have been normal.
    I have fasting blood tests twice a year, as I’m injecting beta-interferon (Rebif 44) and my neurologist, who is a bit of a holistic type, likes to order all the tests he can and not just ALTs.
    I have also discovered that I don’t feel hungry and I’m eating less, which in my case is quite a good thing!
    I eat a very low-carbohydrate diet, with the full support of all my doctors and have done so since 1999. The last test was the first one ever(!) with normal triglyceride levels.
    People with normal metabolisms, who don’t have regular blood tests, may not realise that the effect that Vitamin D3 supplements can have. Maybe with mass supplementation, the obesity levels might drop?

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