Here comes the sun

There is a long stretch of British winter when we get up in the dark, go to the work in the dark and return home in the dark. You can go for whole days without a single photon from the sun landing on your body. But some time in late February chinks begin to appear in night’s mantle. And we are now reaching that magical tipping point, when you can feel the longer days accelerating towards you, curtains become more than just snooper prevention, birdsong returns to the soundscape. The only downside is that sunrises are no longer part of the day’s palette (except for the really keen).

All of which might seem unimportant in these dark days, but daylight is a vital ingredient in our health and well-being. We can sense light even when we cannot see it. Blind people can tell when lights were off or on in. And studies in the 1920s showed that blind mice still responded to the light (that’s how they detected the carving knife presumably). We sense light through a third type of cell in our eye (in addition to rods and cones) these cells are called pRGC photoreceptors.

Daylight also steers our biological clock (the circadian rhythm in science speak). Unconstrained by the light, our daily rhythm is determined by a family of genes and varies between 23.5 and 24.5 hours (explaining larks and owls). However, this natural clock is over-ridden by daylight which acts as a zeitgeber (from the German for time-giver).

This is important because living our lives out of time has a significant negative effect on healthspan. People who undertake shift work have a considerably higher risk of a range of diseases, including cancer and dementia. This is most probably because our body clock sets the production and release of 2 key hormones: cortisol, which rouses us in the morning and melatonin, which calms us down in the evening (the body’s equivalent of caffeine and camomile). Excess cortisol leads to a misfiring of the immune response, enhancing inflammation which has a range of bad effects.

Being outside in the daylight has a slew of other benefits, not least the production of vitamin D. Though care is required as we move into the spring months, when UV intensity is at its highest (preceding the hotter months). So do slap on the sun cream, we can still produce vitamin D, even through the SPF.

The final benefit of the lengthening of days is that it encourages us outside to commune with nature. And whilst winter walks have a value, there is no greater balm for the soul than the fresh green of newly emerging leaves. Trees have a curative, restorative value - as shown in a study in the 1980’s when patients who could see trees self-medicated less and left hospital earlier.

The return of the sun also heralds warmer days, with opportunities to socialise in parks and gardens. So throw those blinds open wide and let the daylight in.