Bill Anderson on the myriad health benefits of sunbathing

Directing screen drama isn’t an obviously idle occupation, but back in 1945 an exasperated Martin Gabel, legendary Hollywood director of all time, was maybe on the path when he gave the immortal instruction to a wildly gesticulating actor: “Don’t just do something – stand there!”

While this specific direction wouldn’t cover an entire drama, perhaps it might be a useful component in our current viral times: standing, or even lying there could protect us from the ravages of Covid-19 if we do it in sunlight and shed a few clothes.

The panoply of effects of sunlight gently caressing our bodies are only just beginning to be understood. We now know that the vitamin D made in our skin by the sun is our main source, not food. D is activated by our liver and kidneys to behave as a hormone that regulates almost all our functions:

In every type of human cell we find “receptors” ready to communicate with this hormone. Preventing conditions as diverse as rickets in our bones and cytokine storms in our lungs, vitamin D acts as a director: inspiring apt performance and curbing excess.

We know D is key to our immune systems but how much can it help with Covid-19?

A small study from Indonesia looked at the outcomes for different levels of vitamin D in groups of patients who had contracted the virus. Those with the highest level of D had the mildest symptoms. In this chart, green is good:

But statisticians were quick to point out, rightly, that because people produce less vitamin D in their skin the older they get, and because old people are more susceptible to Covid-19, this is a confounding factor which might skew the interpretation in favour of higher levels of vitamin D.

Then on 26th April another slightly larger study of 780 Covid-19 patients not only looked at the overall effect of low vitamin D, but also took into account age, gender and co-morbidities. Overall these patients were nineteen times more likely to die of Covid-19 if their vitamin D was low. But even when age, gender and co-morbidities were statistically corrected for, the risk from low vitamin D was only reduced by half – they were still ten times more likely to die, a risk ratio of 10:

Of course this is not a randomised double-blind placebo-controlled trial. It’s association not causation. But there are some very important areas where association is all we have to work with. Like hypertension’s relation to heart attacks. We spend billions reducing blood pressure to avert cardiac death on the basis of an association between the two which indicates we are twice as likely to die from a heart attack if our blood pressure is high. A risk ratio of 2. We don’t have to be statisticians to work out this is much smaller than the risk ratio of 10 for low vitamin D.

But dermatologists will be quick to rightly point out that there is a risk associated with sunlight – we might want to elevate our levels of D, but none of us want to get skin cancer. This might go some way to explaining why our levels of vitamin D have been in decline recently – we’ve been consciously shielding ourselves from direct exposure to the sun. In the USA the percentage of people who have “sufficient” levels of vitamin D dropped dramatically over ten years, leaving over 70% of the population insufficient:

The benefits and dangers of sunbathing are much like the risks involved in driving a car: cars kill, so do malignant melanoma. We don’t allow anyone behind the wheel until we’ve satisfied ourselves they know how to control their vehicle, and fully understand a shared highway code to minimize the risk to themselves and others. We provide road signs to inform of danger, restrict excessive speed and promote safe distance to help millions of us safely travel at up to 70mph. We can never eliminate risk, but we should never stop trying to minimize it.

If sunlight were inherently dangerous we would not be here. We’ve survived for tens of thousands of years without slathering on the factor 30 because we have melanin: the skin pigment that protects us from “overdoing it”. The problem seems to be that melanin evolved for a timescale of gradually increased sun exposure over the course of slowly changing seasons, and can’t cope with the sudden shock when skin that’s been working indoors for months is taken outside by its owner for a good tanning. Unacclimatised, we burn, and it’s the burning that causes the harm. But the protective factor 30 stops the D as well as the damage.

If we could bare our skin to the sun but avoid sunburn as effectively as we avoid car crashes we could potentially save thousands of lives and millions of pounds. And there’s an app for that: http://dminder.ontometrics.com/index.html

Dminder acts a bit like those speed signs at the roadside that tell you exactly how fast you’re going, and warn you if you’re over the limit. It calculates your position on the planet, the current angle of the sun and UV level – you input your local cloud and clothing cover, it tells you how much vitamin D you’re making and alerts you when to either cover up or put on the factor 30. Your data stays on your phone and you don’t burn.

Instead you can safely loll around in the sun, idly not just doing something, while your vitamin D effortlessly increases as your risk ratios begin to fall. Sunlight on our skin even triggers the release of nitric oxide which causes our blood vessels to relax and dilate – the sun lowers our blood pressure too.