Cancer Research UK cautious over new vitamin D research
The benefits of moderate exposure to sunlight may outweigh the risk of developing skin cancer in some populations, according to new research from Norway.
Responding to the research, Cancer Research UK acknowledged the growing body of evidence in support of vitamin D's role in protecting against some cancers, but stressed that this new research does not conflict with current advice on how to enjoy the sun safely.
Dr Joanna Owens, the charity's senior science information officer, said: "It's important to remember that a little bit of sun goes a long way. The amount of exposure you need to top up your vitamin D is always less than the amount needed to tan or burn, which increases the risk of skin cancer.
"Different lifestyles mean that people living in the same country do not all have the same sun exposure so it is impossible to make conclusions about individual cancer risk from a broad study like this that only looks at general trends."
The study, by scientists in the US and Norway, suggests that people in sunnier climates have more vitamin D and that this might protect against cancer.
The researchers estimated how much vitamin D was obtained from sunlight by people living at different distances from the equator. They calculated that people living in Australia (just below the equator) produce 3.4 times more vitamin D than people in the UK, and 4.8 times more than people living in Scandinavia.
When they compared this to cancer incidence and mortality rates, they found an increase in the incidence of skin cancer from north to south, as well as an increase in the incidence rates of bowel, lung, breast and prostate cancer.
But they also saw that people from sunnier latitudes were more likely to survive internal cancers such as lung, bowel, prostate and breast cancer.
Richard Setlow, a senior biophysicist emeritus at Brookhaven and lead author on the paper, published in PNAS, commented: "In previous work, we have shown that survival rates for these cancers improve when the diagnosis coincides with the season of maximum sun exposure, indicating a positive role for sun-induced vitamin D in prognosis - or at least that a good vitamin D status is advantageous when combined with standard cancer therapies.
"The current data provide a further indication of the beneficial role of sun-induced vitamin D for cancer prognosis."
Several lines of evidence have suggested that vitamin D might play a role in cancer prevention.
The vitamin can be obtained from dietary sources like oily fish such as sardines, salmon, tuna and mackerel, as well as in liver and eggs and some fortified breakfast cereals, milk and margarine. It is also made by the skin during exposure to the sun.