Is Avoiding the Sun Actually Killing Us?

Pick up any women's magazine, scroll through any wellness or dermatologist instagram account, sit in any GP waiting room, you will get the same message over and over again. Wear SPF every day. Avoid peak sun hours. Cover up. The sun is dangerous.

Whilst that advice might be saving us from skin cancer, apparently it is quietly contributing to something far more lethal?

I was scrolling through X (previously Twitter) and found a thread posted by Dr Matt Zirwas, a US dermatologist with over 226 publications. This thread has been circulating widely and it makes a case that's hard to ignore. So I went to the primary studies myself. Here's what they actually say.

The Debate Nobody Is Having

For decades, the sun safety message has been built almost entirely around one risk: skin cancer: UV causes melanoma and melanoma kills people and therefore, avoid UV. The logic is clean and the intention is good.

What's been missing from that conversation is everything else the sun does to your body, and what happens when you don't get enough of it. Researchers have been quietly building a body of evidence suggesting that sun avoidance carries its own mortality risk, one that may dwarf the risk of skin cancer in the broader population. The mechanism isn't vitamin D, as many assume. It's something more direct, and the data behind it is harder to dismiss than most people realise. A 20-year Swedish study following nearly 30,000 women found that those who avoided the sun had a life expectancy comparable to smokers in the highest sun exposure group, which suggests sun avoidance carries a mortality risk of similar magnitude to smoking. The effect was driven primarily by cardiovascular deaths, not cancer.

The UK Biobank study of over 376,000 participants found that those with more active sun-seeking behaviour had lower risk of all-cause mortality, cardiovascular mortality, and cancer mortality compared to those who avoided the sun.

So what's actually going on? It turns out vitamin D is likely not the main player here, but nitric oxide. UVA exposure mobilises nitric oxide reserves in the skin, causing vasodilation and reducing blood pressure (this is vitamin D-independent mechanism that helps explain the cardiovascular benefits of sun exposure). Blood pressure is the single largest driver of cardiovascular death globally. A mechanism that directly lowers it matters enormously at a population level.

The vitamin D supplement angle, meanwhile, has largely collapsed under scrutiny. Two of the largest randomised controlled trials of vitamin D supplementation; each with tens of thousands of participants, found no meaningful reduction in cardiovascular disease or cancer. High vitamin D levels appear to be a marker of sun exposure, not the cause of the benefit. The sun itself is doing the work.

What It Means for You?

None of this means you should bake yourself into oblivion. The evidence points to moderate, regular sun exposure (not burning) and not obsessive avoidance. The risk from intermittent overexposure (the classic holiday sunburn) is real. The risk from consistent moderate exposure appears to be far lower than the risk of getting none at all.

So think about these:

• Getting outside for 20–30 minutes around midday, when UVB is strongest, several times a week gives your skin the UV it needs to trigger nitric oxide release and support cardiovascular health. If you can, expose your arms and legs where possible because the more skin surface, the more efficient the response.

• If you live somewhere with low sunlight for much of the year like the UK, northern Japan or Scandinavia, this matters more, not less. The UK Biobank researchers concluded that the benefits of UV exposure may outweigh the risks in low-sunlight countries. In other words: if you live somewhere cloudy and grey for a large chunk of the year, being cautious about the limited sun you do get is probably the wrong call. Those precious sunny days aren't something to hide from but they're something to use.

• Try your best and don't burn! Burning is where the skin cancer risk concentrates. Gradual, consistent exposure is what the evidence supports and not long unprotected sessions that leave you red. Consistency over intensity.

• Sunscreen still has a role in high-exposure situations like long days outdoors or a long day at the beach, reflected sun near water or snow, or if you have a personal or family history that warrants extra caution. But slathering SPF 50 on every morning before a commute may be trading one risk for another.

Anyways all in all: the sun is not the enemy. Burning is. Obsessive avoidance appears to carry a cost that the public health conversation has been slow to acknowledge.

Oh, if you struggle with knowing how long you should be exposed to sun, check this interactive app to guide you:

Inspired by a thread from Dr Matt Zirwas (@mattzirwas on X).