Recent research, some of which we helped fund, suggests that melanoma and bowel cancer patients with high levels of vitamin D – the “sunshine vitamin” – may survive for longer.
But should people with these cancers be rushing for the sun lounger or sunbed? And does this conflict with our advice about staying safe in the sun?
How is vitamin D linked to cancer?
Ed has already written at length about vitamin D, UV exposure and cancer, so we’d recommend reading his two posts (Does vitamin D protect against cancer? and Do we need more sunlight to make enough vitamin D?) as background.
In summary, there’s tantalising evidence that vitamin D could play a role in preventing some cancers, in some circumstances. But ‘everyday’ casual sun exposure – rather than sunbathing – probably gives most people enough vitamin D.
The link between cancer survival and vitamin D comes from two scientific papers. The first is from Professor Julia Newton-Bishop and her Cancer Research UK-funded team in Leeds, along with colleagues in Birmingham and the US. They measured the levels of vitamin D in the blood of 872 melanoma patients at the time they were diagnosed, and cross-matched these with clinical information about how each patient fared.
The second study was carried out by researchers at the Dana Farber Cancer Institute in the US, and involved 1,017 bowel cancer patients. Although these researchers didn’t directly measure the levels of vitamin D in the patients’ blood, the scientists asked them questions about their diet, supplement use and sun exposure. This enabled them to work out an estimate of vitamin D levels in the blood at the time of diagnosis.
Both studies compared the patients with the highest levels of vitamin D to those with the lowest, to look for links between their vitamin D levels and how their disease progressed.
What did the studies find?
In the first study, melanoma patients with the lowest levels of vitamin D were a third (30 per cent) more likely to relapse after treatment than those with the highest levels. And those with the highest levels of vitamin D tended to have thinner (i.e. generally less dangerous) tumours when they were diagnosed.
In the US study, patients with highest estimated vitamin D scores were half as likely to die from bowel cancer, compared to people with lowest scores. Although the researchers only used so-called proxy measures, rather than actually measuring vitamin levels in the blood, it’s certainly an interesting finding that warrants further investigation.
What does it mean?
The results suggest that people with melanoma or bowel cancer might benefit from increasing their vitamin D levels, either through diet, supplements or UV exposure. But it’s important to note that vitamin D supplements (and excessive amounts in the diet) can potentially cause harm if taken in large doses without medical supervision.
We strongly advise cancer patients to talk to their doctor if they are concerned, before considering taking supplements – especially since there’s evidence that some vitamin supplements can have unintended consequences. Moreover, vitamin D from supplements doesn’t appear to be regulated in the body as tightly as vitamin D from the sun – and there’s still a lot of uncertainty over what the ‘best’ dose is.
And we certainly don’t recommend that patients go overboard on the beach or sunbeds to top up their vitamin D. We know that we all need a bit of sunshine in our lives. But we also know that excessive UV exposure (from the sun or sunbeds) and sunburn are major risk factors for melanoma.
Through our SunSmart campaign we encourage everyone to enjoy the sun safely, and most people make more than enough vitamin D after a just a short time in the sun – less than the time it takes to burn.
Certain groups of people – the very young, the very old, the housebound, and people who wear full-body coverings – may benefit from vitamin D supplementation. And researchers are currently discussing whether very fair people (who redden or burn in strong sun in a matter of minutes) who excessively protect themselves from UV may actually not make enough vitamin D. But this is currently an idea that needs more research.
The area of vitamin D and cancer is fascinating and controversial, and scientists around the world are actively discussing and studying it.
Here at Cancer Research UK we’re continually reviewing the scientific evidence around vitamin D, sun exposure and cancer risk and adjusting our health messages whenever new evidence emerges. And we’re actively funding research into vitamin D levels and how this relates to UV exposure, to try to illuminate some of the grey areas in this most intriguing of topics.
This st0ry has also been covered on the NHS Choices blog
Ng, K., et al (2009). Prospective study of predictors of vitamin D status and survival in patients with colorectal cancer British Journal of Cancer, 101 (6), 916-923 DOI: 10.1038/sj.bjc.6605262
Newton-Bishop, J. et al (2009). Serum 25-Hydroxyvitamin D3 Levels Are Associated With Breslow Thickness at Presentation and Survival From Melanoma Journal of Clinical Oncology DOI: 10.1200/JCO.2009.22.1135