31st July 2016

Welcome to July's health newsletter. It's been a month full of sun in the UK so let's explore sunlight, circadian rhythm and our health. As ever we will consider how our modern lives conflict our evolutionary history.

Enjoy, James.

Reading time: 6 mins

Sunlight, screens and circadian rhythms

If you don't have much time, watch this short video where I touch on the topic of screens, sleep and sunlight. For those interested read on...

Summer is here

The majority of health experts focus on nutrition and exercise. Get either of these two wrong and your health will suffer. But an aspect that gets less attention is how the light affects our health. And this month I heard one man say that managing the light in our lives is more important than either of these two!

What I’m learning is fascinating and enlightening. It gets a bit deep and can run counter to conventional wisdom. And it's been challenging me and my use of modern technology, sunscreen and sunglasses. 

It is impossible to ignore that:

“Our health today is deeply connected to our evolutionary history and the mismatch with our current environment. “

I’m not a Luddite, in fact, I predict that technology will make being healthy much easier. But we must use technology to help match our environment to our biology. When we do so we will reduce the preventable diseases that are causing so much suffering today.

The past

Just imagine being alive 50,000 years ago…

 no TV...

no TV...

 no internet and no...

no internet and no...

 Pokemon GO!

Pokemon GO!

Just you, the tribe and your natural environment. The sun dictated when we could work, when we could explore and when we had to take shelter. Without so much distraction it’s not surprising we studied the stars and planets. Let alone coming up with mythical gods to explain our existence on earth. 

The night also bought many dangers. Our inner chimp likes to feel safe and won’t let us sleep unless we are safe. Just think of our friendship with dogs, fire and big homes. Anyway back to the point, day and night.

Central to our existence is day and night. We are diurnal animals, sleeping at night and adventuring during the day. We’ve lived this way for millions of years. All mammals have developed a biological clock attuned with this cycle.

All our biological processes became tied to this daily light cycle. The suprachiasmatic nuclei (SCN) in our brain, is known as the ‘master clock’. It communicates with our organs which have their own circadian rhythms.

The light that comes through our eyes goes straight to the SCN. The SCN then controls the release of cortisol and melatonin. This regulates our sleep- wake cycle. Cortisol the stress hormone wakes us up in the morning, keeps us awake in the day and saves our life when in danger. Melatonin is the sleep hormone, responsible for making us drowsy after dusk. Melatonin is also a powerful endogenous antioxidant. It repairs and regenerates cells throughout the body and brain. 

Controlling these two master hormones is fundamental to good health. Disrupting the biological clock causes metabolic disorders such as Type II diabetes and obesity. Studying shift workers, pilots and flight attendants shows increased incidence of disease.

Light bulbs

Light bulbs became a feature of daily life a mere 100 years ago, a blink of the eye in our evolutionary history. Before that we relied on the light from a fire, a candle or a lantern. Now I’m sure cavemen and women all over the world have been staying up past their bedtime, just like we do today, but the problem we have today is that our modern lights disrupt our biological clocks.


Unfortunately blue light from incandescent, fluorescent and LED bulbs suppresses the release of melatonin. This interferes with the sleep cycles necessary for regenerative sleep. As I have said before getting a good night’s sleep is more than just clocking in the hours.

Blue light is just a specific frequency of light. The frequency of light changes throughout the day. The morning and midday sun has more blue light in than at the end of the day. Whereas in the evening there is more red light. These changes get detected by our eyes and our brain and control our circadian rhythm.

Many of us today are suffering from natural light starvation! By working indoors we aren’t exposed to enough light to regulate our biological clock. But there is also a timing problem. By exposing our eyes to too much blue light in the evening the problem gets exacerbated. By using blue light emitting technology after sunset we again disrupt the natural cycle.

Perhaps the easiest solution would be to return to the caves on mass, but we all know that’s not going to happen. So we must use technology to solve the problems it’s created. We can use technology to mimic our natural environment. We can choose to do any of the following:

  • Choose bulbs that emit less blue light like incandescent bulbs
  • Install adjustable LED bulbs like Philips Hue  
  • Install dimmer switches in rooms we relax in before bed
  • Use candlelight just before bed
  • Have a techno curfew before bed
  • Use F.lux on computer screens
  • Switch on Nightshift mode for iPhones and iPads
  • Install apps like Twilight on Android devices

Modern Careers

This might seem a little extreme but many of us live lives like caged animals. Many jobs involve working inside, under fluorescent lighting, that is damaging our health. It’s well known that animals in captivity don’t live as long as their wild counterparts. We forget that we are animals and our natural environment is outside.

I understand that society would collapse if everyone stopped working indoors. But there are steps we can take to limit the damage. On the extreme end you could go to live in the mediterranean and work outside. Or you could just change our work environment to include more natural light.

When I’m teaching in classroom at school, the first thing I do is turn the lights off, open the blinds and windows. So many classrooms I enter have the blinds shut and lights on. When I let the natural light into the classroom so many children wince and complain that it is too bright. In an unsympathetic manner I call them troglodytes and tell them to get used to it! But I fear this sensitivity is a big health concern. It's the result of spending too much time inside and too much blue light exposure.

Why do we love the sun?

There's a reason why so many of us love the sun and enjoy going on holiday. You know that euphoric feeling when winter ends and the days start getting longer. We know the benefits of spending more time out in the sun even if we don't know the biological mechanisms. If any of you have lived abroad you'll know how good it feels.

Managing the sun

For complex reasons we have come to fear the sun. But for millions of years we were sun worshipers. This fear, spread by pharmaceutical companies, makes us reach for sunscreen and sunglasses. But these don't always protect us in the ways we're taught.

For millions of years humans have done quite well without sunscreen and sunglasses. I once thought my fair skin was mega sensitive to the sun. It turns out it just need a bit of acclimatisation and a bit of care around the midday sun.

Before you head off on your holiday this summer, read the ingredients on the back of sunscreen. Know that what we put on our skin gets absorbed inside ourselves. These unnatural chemicals have an impact on our biology, often in undesirable ways. 

Also think about why people who live in hot countries take their time to cook and eat lunch. And why they take a siesta after lunch. When I lived in Italy this is exactly what I lived and it was bliss! 

For me, the key is to manage the sun:

  • Know your tolerance to the sun and don’t over do it
  • Build up your tolerance over time
  • Avoid the sun around midday 11- 3pm
  • Don't spend more than 20 minutes out in the midday sun
  • Don’t use sunscreen unless you have to
  • Cover up or seek the shade during these times
  • If you have to be outside choose non toxic varieties of sunscreen
  • Enjoy the sun in the morning and evening as much as possible

In the past I've spoken of the importance of sunlight in making the steroid hormone vitamin D. But our interactions with the sun runs much deeper than that. Our circadian rhythm sets off a chain of biological processes that keep us healthy.

Within our DNA and biology we have the tools to protect us from the sun. We are hardwired to adapt and survive. I don't have all the answers but consider the past when considering the future. We have a lot to gain from the sun but it needs respecting.

Thanks for reading,

James @


P.S. If you want to learn more about light check out Dr Jack Kruse. He was the man who introduced me to the benefits of cold showers about 6 years ago. A little warning though, his message science heave and his delivery can be a little full on.


Health is central to everything I do but fat loss is important! Check out this blog to learn more about the psychology of health and fat loss.


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There we are, July's health newsletter. As ever please feel free to forward this email onto friends and loved ones. The healthier we all are, the better the world will be, for everyone.

All the best

James @


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