The health expert Prof Tim Spector has come under fire from fellow scientists after he suggested people should stop using factor 50 sunscreen all year round.
Spector cited a recent mouse study that suggests vitamin D levels may be an important factor in cancer immunity and immunotherapy success, saying the research is “another reason to stop using SPF 50 all year round which blocks our natural defences”.
However, a co-author of the study disputed such conclusions.
“Sunlight can help our bodies make vitamin D but sun exposure is also a clear risk factor for skin cancer. As we can also get vitamin D from diet, it is easy to avert possible vitamin D deficiency while minimising harmful exposure to sunshine. Our study does not suggest that the application of sunscreen is in any way detrimental to health,” said Prof Caetano Reis e Sousa from the Francis Crick Institute.
Spector, who made the statement on X, saw his post initially flagged with a context box that stated: “The linked study is a pre-clinical study based on mice alone. The suggestion that this means humans can reduce SPF use is a huge jump which is not evidence-based, and should be read with caution.” However he subsequently reposted on the platform.
The posts were met with a backlash from medical professionals.
“This is a frighteningly inaccurate post which may create huge damage. Academic authorities with a large followership should be more mindful than this,” Adriano Aguzzi, a professor and director of the Institute of Neuropathology at the University of Zurich, claimed on X.
Speaking to the Guardian, Spector reiterated his view.
“Studies have shown that, in people with melanoma, lower levels of vitamin D are associated with poorer outcomes and thicker tumours – a measure of disease severity.”
“Other research showed that melanoma patients who went on a sunny holiday before diagnosis had less thick tumours. The same study showed that people who had sunny holidays after diagnosis were less likely to experience recurrence.”
Spector said the risk of developing melanoma was largely dependent on genetics.
“So, while the vast majority of people do not need to wear SPF 50 all year round in the UK, certain people do need to be more careful if they are planning to be in the sun for long periods. These individuals include those with a family history of melanoma, pale skin and freckles, and those with a large number of moles,” he said.
“But even for these individuals, wearing SPF 50 for 365 days a year is likely excessive and likely to leave them vitamin D deficient.”
Dr David Robert Grimes, a scientist and author of The Irrational Ape, criticised Spector’s post.
“It is utterly wrong-headed to extrapolate an exploratory mouse study to humans, an error made all the more egregious by a haphazard inference we should use less sunscreen to reduce cancer risk,” he said.
“This flies in the face of over 100 years of clear data linking sunlight to skin cancer, and sunscreen as a highly effective way to prevent skin cancer. To make matters worse, most recent high-quality trials and meta-analyses have found no effect of vitamin D on mortality, and there is also no evidence that sunscreen inhibits vitamin D production anyway,” he added.
Antony Young, an emeritus professor of experimental photobiology at King’s College London, said there was no need to use sunscreen all year round in the UK – although the practice was unlikely to be harmful.
“The dose of ultraviolet radiation B needed to make vitamin D in the skin is much lower than that for sunburn,” he said.
Young added that while there were no studies on the effect of SPF 50 sunscreens on vitamin D, his own work had shown correct use of SPF 15 during a week’s sunny holiday in the Canary Islands prevented sunburn yet allowed excellent vitamin D production.
“The problem is that people do not use sunscreens correctly, which means typical use of SPF 50 will give an SPF in the region of 15, so unlikely to have a major effect on vitamin D,” he said.
It is not the first time Spector has raised doubts about sunscreen. Writing on X in 2022, he stated that sunshine only accounted for a small proportion of melanomas and death rates had not changed for 40 years. “But charities doctors and sun cream manufacturers benefit,” he wrote.
