“So we are abusing our circadian system by the misuse of light at night.”
We have evolved with the consistently predictable, daily rising and setting of the sun. It’s something our biology have taken for granted for millennia.
On average 12 hours of light followed by 12 hours of dark with seasonal variations with increase distance from the equator.
Our biology has evolved to function best with bright days and dark nights and consistent light/dark cycles. Our bodies have evolved to use natural light and dark to tell the time of day, month, and season and to adjust our behaviour and physiology accordingly.
At night the only light our ancestors saw, was that of the moon, the stars and more recently firelight. They would have seen a 100,000 fold difference between light and dark (sunlight to moonlight). Today many people may only see a 100 fold difference between light and dark, due to days spent indoors and the use of artificial light at night. Industrialisation moved people from spending most of their day outside working on the land to spending most of their time inside dimly lit buildings. But it wasn’t until this century that exposure light at after dark became ubiquitous and normal for most people in industrialised countries.
Every cell in our body has an internal clock that keeps us in-sync with our spinning planet. We have a central clock in the SCN in the brain which is reset by light and which keeps all the other clocks in sync.
At dawn our eyes receive sunlight which resets (entrains) the central clock in the brain. Around 12 hours later our pineal gland, located in the middle of our head, begins its nightly secretion of Melatonin into the blood stream. Artificial light at night suppresses this melatonin flow. The brain perceives the blue light hues of the artificial light as day and so does not start it nightly secretion until the lights are switched off.
Melatonin is well known as a sleep hormone, it is also the most potent antioxidant and a multi-functioning anti-cancer agent. Once it is dark, the levels of Melatonin in the blood rise slowly at first then accelerate up until about 3 am when they peak and then begin to fall back down to low daytime levels. These nightly levels have been shown to have very powerful antioxidant and anti-cancer effects.
Along with melatonin the pineal gland also secretes other anti-cancer agents. As a result rather than taking melatonin it may be better to maximise your natural pineal gland output as it includes these other pineal extracts. Taking melatonin may have adverse effects on your bodies own production.
Our nights began being illuminated in a significant way with gaslight in the early 1800s and then the invention of the electric bulb by Thomas Edison which became common place in the early 1900s. Brighter and whiter artificial lighting now pervades the modern world after dark. Our brains see this artificial light as ‘day’ and the nightly secretion of Melatonin is delayed until the lights go out.
Our daily up down rhythm is of Melatonin is suppressed as our ‘dark’ nights are now shorter, brighter, irregular and disrupted.
SHORTER: Shorter nights mean our duration of melatonin is reduced from the optimum 11-12 hours.
BRIGHTER: Nights are often illuminated, from street lighting coming in from outside, or from lights left on all night long, this further suppresses melatonin.
IRREGULAR: The sunset our ancestors would have experienced would have been at almost the same time everyday, with steadfast regularity. In our modern world our sunset is when we switch off the lights and screens of the tv, computers and phones. The timing of which can vary greatly from day to day. This disrupts our biological clock, and weakens our rhythms.
DISRUPTED: If we do sleep in the dark, our dark night may be interrupted by looking at the screen of our phone to check the time, or turning a light on to go to the toilet, during the night. This tells our biological clock that it is dawn and stops the production of melatonin.
In 2002 scientists discovered that it is predominantly the blue light wavelength, that our brain recognises as ‘day’. Special blue light receptors in our eyes send the messages to the master clock telling the brain that it is day and the master clock tells the pineal not to secrete melatonin. White light contains a high proportion of blue light, especially ‘colder’ white light. The cold light of modern energy saving light bulbs and LEDs emit far more blue light than their predecessors. Computer screens, televisions, tablets and smart phones all emit a large amount of blue light wavelengths.
This was an important discovery because it means that if we remove this blue light from our evenings we can regain our optimal 12 hours of melatonin without having to switch everything off and stumble around in the dark. Studies have shown that after removing this stimulating blue wavelength, people found it easier to fall asleep, they had a deeper nights sleep and felt more rested in the morning.
Melatonins anti-cancer effects
Every cell in the body, including cancer cells have receptors for melatonin. It literally tells our cells that it is night time, and time to rest.
Melatonin is powerful antioxidant and helps activate the immune system. It prevents cell mobility that causes cancer to spread and prevents the growth of blood vessels that provide nourishment for cancer cells. Melatonin blocks oestrogen’s cancer stimulating effects and the ability of tumours ability to stimulate localised production of oestrogen. It interferes with the cancer cell cycle leading to cancer cell death and blocks Telomerase’s ability to make cancer cells immortal. Melatonin promotes normal daily rhythms which helps prevent cancer and prevents the cancer promoting action of certain genes. It accelerates the process by which immature cells become differentiated mature cells- preventing cancer. Melatonin alters fat metabolism and interferes with the ability of many tumours to use the fatty acid linoleic acid as a growth signal, this causes tumour metabolism and growth to be shut down. Melatonin has been shown to greatly enhance the effectiveness of tamoxifen a drug used to treat breast cancer.
All of these actions mean that our bodies own Melatonin and other pineal agents can have a huge impact on both the prevention and treatment of cancer.
Animal and human studies
A study of turkeys showed ovarian cancer tumours shrink and in some cases disappear completely in long nights- 8 hours of light and 16 hours of dark (L:D 8:16) conversely it was found that tumours grew larger in the turkeys that were subject to 16 hours of light and 8 hours of dark (L:D 16:8).
In 2005 Scientist Blask, Brainard and others took blood from human female volunteers under three conditions; 1) during the day, 2) at night and 3) at night after light exposure. The blood from the three conditions was then supplied to rats that had human breast cancer tumours grafted on to their backs. They found that the tumours did not grow or grew very little with the melatonin rich night blood. They found that the tumours grew rapidly when exposed to the day blood, and ‘night with light exposure’ blood, both of which contained no melatonin.
Very low levels of light (0.2 lux) eg light leaking under a door can increase rates of tumour growth in rats (Dauchy RT et al. 1997).
Human studies have shown;
Significantly higher cancer risk in shift-workers, particularly rotating night shiftworkers, who have minimal night time levels of melatonin.
A 30% lower cancer risk in totally blind people, who have melatonin all the time.
Epidemiological studies have shown that cancer is 5 times more prevalent in industrialised societies compared to non-industrial societies.
One study by Verkasalo showed women who consistently sleep 9 hours or more have ¼ rate of breast cancer of women who sleep 7 hours of less.
A study of outdoor artificial lighting at night and breast cancer incidence in Israel found that women living in neighborhoods where it was bright enough to read a book outside at midnight had a 73% higher risk of developing breast cancer than those residing in areas with the least outdoor artificial lighting.
There are easy steps to increase your body’s nightly melatonin production, returning it to the ‘normal’ levels in which we have evolved, in order to protect your health. Getting daylight in the day, going amber in the evening, and sleeping in dark, much like we have evolved being outside during the day, having firelight in the evening and sleeping in the dark.
It is important to get a minimum of 30 mins outside each day. This can be 10 mins in morning, 10 mins, at lunch and 10 mins in the afternoon. This entrains your master body clock (SCN) and helps increase melatonin levels at night.
You can remove bluelight wavelengths in the evening by protecting your eyes with amber glasses and or removing the blue light from the light source.
Adjust your evening lighting to yellow or amber. Yellow or amber energy saving bulbs on amazon
Install blue-blocking apps on electronic devices eg f.lux on computers twilight on smart phones, or use yellow film screen protectors electronic devices.
Turn the contrast and brightness down on your television and cover with yellow film.
In situations where lighting cannot be changed- blue blocking glasses can be worn eg when out at night, at a friends house or in hospital. There are regular blue-blocking glasses and fit-over glasses, which you can wear over normal glasses.
When you go to bed, you need to sleep in total darkness.
If you find you often fall asleep with the light on, you could use one of these Ansmann plug sockets which turns off automatically after 15mins, 30 mins, 1 hour, 2 hours etc. Or plugs that you can switch off with a remote control
If there is light coming in from the street, use thick curtains or a black-out blind or sleep with an eye mask on if its easier.
If you need to turn on a light to go to the toilet at night make sure it dim and yellow, amber or red.
Pineal gland is susceptible to damage by high levels of fluoride via the displacement of iodine, which can reduce your melatonin production. If you live in an area with fluoridated water you can reduce your fluoride consumption by only drinking filtered or bottled water. You can ask your GP for an iodine deficiency test and you can increase iodine naturally by taking sea kelp or eating eggs, fish and sea vegetables.
Here is some more info about it http://articles.mercola.com/sites/articles/archive/2013/06/29/iodine-deficiency-risk.aspx
It is not just sleep and cancer that our effected by reduced sleep and reduced melatonin. Optimising natural melatonin can help a variety of conditions, or put another way a lack of melatonin may show itself in variety of conditions depending on a persons genetic dispostion and other environmental factors.
Other diseases/medical conditions which are reported to be affected by reduced sleep and or reduced melatonin production include; obesity, diabetes, heart disease, autism, altzeimers, parkinsons, depression, bipolar, schizophrenia, auto-immune diseases, migraines.