By now, most of us are familiar with the idea of getting outside to balance our circadian rhythms. If you’re struggling with sleep or inertia on waking, the experts generally recommend getting outdoors as quickly as possible in the morning to let the light do its magic.

We’re also aware that the sun plays a big role in our vitamin D levels. During autumn and winter, most of us could benefit from vitamin D supplements, but from late March onwards, the sun’s rays (in this part of the world) are strong enough to fire up our vitamin production.

What you may not know, however, is just how critical natural vitamin D absorption is to our longevity. According to 2020 study published in the International Journal Of Environmental Research And Public Health, insufficient daily sun exposure (and therefore vitamin D) might be responsible for a whopping 480,000 premature deaths in Europe. It went on to claim that a lack of sunlight could play a role in the increased rates of cancer, type 1 diabetes, dementia, asthma, multiple sclerosis and heart disease.  

More recent studies have looked at the differences in lifespans of those who actively take in the sun and those who don’t. One followed 30,000 women in Sweden for 20 years and found that those who actively avoided the sun had the same cancer risk “of a similar magnitude as smoking”. In fact, the study concluded that “nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group”.

It’s interesting that although vitamin D is at the centre of these findings, all of these studies talk explicitly about sun exposure and not vitamin D supplementation, suggesting that supplements are something we should certainly consider during autumn and winter but that the sun is a better source in the long term. 

Now, we know that having too much sun exposure can lead to skin cancer so the question really is: how much sun is the sweet spot?

A study looking at the vitamin D requirements of white Brits found that 9–13 minutes of lunchtime exposure between March and September in ‘season-appropriate clothing’ was optimal. If you’ve got darker skin, you may want to spend slightly longer, but recent studies have actually concluded that melanin doesn’t have the massive inhibitory effect on vitamin D as previously thought. Researchers recommended a maximum of 30 minutes of unprotected sun exposure for all skin colours.

That’s roughly the same advice as a 2019 Swiss study that concluded that 15 minutes during the spring was enough. Their researchers recommended taking a ‘little and often’ approach to exposure to avoid sunburn but fill up on vitamin D. 

They also concluded that it was impossible to reach the daily dose of vitamin D required during the autumn and winter in Switzerland – and the NHS here also recommends adults supplement the vitamin between September and March. 

But the Swiss researchers were also careful to point out that the amount of time it takes to load up on the right amount of vitamin D and having an increased risk of sunburn “might only differ by a few minutes”, so breaking the amount of time you spend unprotected in the sun might be the best way to go.  

For most people, 15 minutes isn’t a big ask. It’s a five-minute cup of tea on your balcony/in your garden/on your porch in the morning and a 10-minute walk at lunch. Or you might want to head for a 25-minute stroll/run after work once the sun’s lost a bit of its power, in which case, you probably want to spend a little longer outdoors.

The good thing is that cloud cover doesn’t impact vitamin D’s ability to get into the skin. Just as you could get burned on a cloudy day, UV rays and vitamin D can power through the haze. So it’s always worth popping out first thing, even if it’s a dull day.

Image: Getty