If you’re in the northern hemisphere you have probably commented – more than once –on how dark it is at the moment (if you’re anything like me, anyway). We’re used to the idea of ‘wintering’ now (and if you’re not, read Katherine May’s wonderful book of the same title) – hunkering down in the darkness, allowing our natural circadian rhythms to let us slow down a little. Hibernation isn’t just for animals, I always think! We humans are creatures of light and dark too.
That certainly plays out when it comes to longevity. It’s not that the dark winter months cause us to age more rapidly, but we do need the right light at the right time. In winter we tend to get less bright morning light. I certainly felt hugely energised by the stunning Norfolk sunrise, pictured above. Light regulates the body’s internal master clock, managing our sleep/wake cycle, cortisol rhythm, melatonin release, inflammation and blood glucose control. When winter is dark, but our lives are full of artificial light, we lose the strong daily time cue, causing our body clock to drift. The end result? Circadian disruption linked to higher risk of metabolic syndrome, cardiovascular disease, depression, and cognitive decline.
Too little light in the day, too much at night
That light-dark imbalance also results in worse sleep and therefore also potentially poorer glymphatic clearance (the brain’s overnight clean up). And that’s without the more obvious issues like we create less vitamin D and tend to crave stodgier warming foods, be less social in winter and less physically active (apparently 61% of Brits stop exercising all together in winter, but I find that hard to believe…)
Annabel wrote here about how too little light in the day, and too much artificial light at night can increase diabetes risk. The Dutch researchers speculated that the trillions of gut bacteria living within us need the age-old rhythms of light days and dark nights in order to properly digest our food.
Better timed light
No wonder SAD lamps are so popular – and well researched. They pump out broad spectrum white light – giving us a blast of ‘daylight’ and resetting those internal clocks. Multiple meta-analyses have linked them to light therapy significantly reduced depressive symptom severity compared with control conditions.
It’s not that we need more light in winter to age well, we need better timed light – more bright light in the morning and dimmer, warmer light in the evening. Look for light bulbs that are ‘warm-dim’ – 2700K or 2200K, flicker free and dimmable. Ideally our evenings would be lit by lamps and candles rather than harsh overhead light, but I know that’s not always possible.
Firing up the mitochondria
There’s been a lot of chat recently about red light / near-infrared light (technically known as photobiomodulation) which may support longevity by improving mitochondrial function (the ‘batteries’ of our cells). The theory is that red / near-infrared wavelengths are absorbed by mitochondria, which can help them produce and transport energy more effectively, reduce oxidative stress and support cell repair signalling. As we age, we want our mitochondria to be – literally – firing on all cylinders, helping each cell stay energised.
This type of light has also been linked to relief from chronic pain, dampened inflammation, improved skin and eye health and better muscle recovery. I’d love to know if you’ve used it – let me know in the comments below. Thanks to the Age-Well Project reader who put me onto the work of Prof Glen Jeffery at University College London in this field. He was interviewed on the Huberman podcast at the beginning of December – you can find that on YouTube here – or wherever you get your podcasts.
Light and cognition
I’ve been experimenting with another form of light: 40Hz. This light frequency is in the brain’s gamma range, which is linked to attention and focus, memory processing and communication between brain networks. The theory is that 40Hz stimulation helps ‘smoothe out’ the brain’s gamma rhythms, allowing for better signalling, lower neuroinflammation and better detoxification. Of particular interest to me, as a brain health coach, is research by Dr. Li-Huei Tsai at MIT. It found 40Hz light reduced amyloid build up (linked to Alzheimer’s) in mice and improved sleep and attention in older adults.
Now, near my desk, I have a small lamp which flickers 40 times a second – hence 40Hz. It’s just in my eye line and – perhaps surprisingly – isn’t annoying. I have it on for an hour a day and just carry on with my work. The lamp I have is a Beacon40 – I got it from the States, but similar lamps are available in the UK. Is it changing my brain? I don’t know yet. I’ll report back with updates!
Susan
Thanks for the information about the benefits of different wavelengths of light. Have heard about red light but not about Professor Jeffery (and the work he’s doing on eyesight) nor anything about the 40Hz part of the spectrum.
Just wondering at the moment if living at a high northerly (or southerly) latitude has its downsides, not just because of the weakened power of the sun’s infra-red radiation but also the change in timing of morning light through the seasons, meaning that even if you’re regularly getting out in the light first-thing in the morning you’re actually setting the body clock at different times throughout the year.