Using A Computer At Night

It is amazing to stop and think about the pace at which technology is changing. Computers, the internet, mobile phones – all of these are fairly recent additions to our lives. But these advancements in technology have changed the landscape for how we work. More people are working in desk jobs than ever before, with farming and other manual labour being carried out by machinery more and more.

These advancements in technology have also meant a blurring between work and non-work time. People will bring laptops home and work in the evening time. Or they can check emails on their phone in bed. And even when people aren’t working, the boom in social media means that people are spending an inordinate amount of their time staring at a screen. Whether it be a laptop, a tablet or a mobile phone, people are regularly being bathed in the glow of these devices.

And it’s this glow that I wanted to talk about. Humans have evolved over millions of years, well before the invention of fire, lights, computers or television. From an evolutionary perspective light signalled daytime.

The sun rising in the morning stimulates the body to produce hormones like cortisol. While cortisol is typically thought about as a stress hormone, it also has lots of everyday functions. It actually rises in the early morning, peaks around 9am and is used to get the body moving – shifting it from sleep to awake mode.

Unfortunately the body doesn’t really differentiate between the sunlight beaming in through your window and the light beaming out of your iPad or iPhone. And this becomes a problem at night time.

At night your body should be preparing to rest. Cortisol should be lowest in the evening time allowing other hormones relating to sleep and repair to increase. But if you are looking at a device that’s emitting a glow that the body thinks is the sun, cortisol is going to stay high, or at least higher than it should be.

Cortisol Circadian Rhythm 7 Health

Light is broken into different colours and wavelengths and these various ranges have different effects on the body (this is something I talked about previously in this article). The light that seems to cause the most issues in the evening and in regards to cortisol is blue light.

So if we can find a way to cut out this blue light then the damage from using devices in the evening can be severely minimised. Thankfully there is such a thing, and it is called f.lux

f.lux is a free computer program that runs in the background while you are using your computer. It works by making adjustments to the colour of the screen based on the time of day (it links into your time zone) and the amount of brightness in the room. During the day time you don’t notice any difference but as the sun starts to set and the light gets darker outside, the colour temperature of the screen adapts.

As dusk approaches, your screen gradually changes to a warmer, easier on the eye, colour setting. The first time I tried f.lux, it just seemed to me that the screen was a little more red. It took a day or two to adjust to this new hue, but now I don’t even notice it. I would find it almost unimaginable to go back to my pre-f.lux display settings and the effect of disabling f.lux at night is not unlike staring at the sun and you can quickly realise how much of an impact it’s having.

f.lux 7 Health

f.lux works on both Mac and PC and I would highly recommend installing it. While I typically recommend that people don’t use their laptop or computer in the evening, I am also a realist. I know there are times when I have to work late and if I can be minimising the issues while doing this then all the better.

f.lux can work on an iPhone and iPad but you have to jailbreak it to get it to work. I haven’t done this (and don’t necessarily recommend that you do too) but it is possible if you want to go down that route. For android phones and tablets there is an app called Twilight that does the same thing. I use Mac products so don’t have any experience with Twilight but have heard good things about it.

I have downloaded a program called Koalo for my iPhone that takes the blue light out of the screen but it only works when searching the internet using this specific app. If using the iPhone to look at emails or check Facebook then Koala doesn’t do anything, so it is pretty limited in what is can do.  My search for an alternative continues.

I am a big proponent of finding small changes that can make a big difference. Sleep is so crucial to good health and in our technological world it is easy to negatively affect this. Installing f.lux is simple and within a couple of days you won’t even know it’s running. But it will be making a positive impact and with no effort on your part.

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Chris Sandel is the founder of He is a nutritionist, working with clients on a one-on-one basis, as well as creating online trainings and products about health and nutrition. He is the author of The Health Trap: Why "Healthy" Eating Isn't Always Healthy which is available on Amazon UK and Amazon USA.

Chris has three free emails series. One is on how to quit dieting. One is on simple tests you can do at home. And the other is his take on the world's healthiest foods.


  1. Thank you! I’ve just downloaded the software and I’m feeling more comfortable already.

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