The importance of melatonin and why we need to sleep in a dark room.

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We produce melatonin at night when we sleep.  It helps us sleep well and this gives our body a chance to recover and repair itself.  For this reason alone, melatonin is very important for our health.  However, as mentioned at the end of the video, melatonin is also an antioxidant and an anti-cancer agent.

There has been a huge amount of research done on melatonin – what suppresses it, on melatonin levels in the elderly, those with Alzheimer’s disease and those with depression and the effects of light and melatonin production in shift workers, plus their prevalence of cancer possibly due to the disruption of their circadian rhythms and messed up melatonin production.

We principally produce melatonin deep in the brain, in the pineal gland as a response to falling light levels at night.  The body makes its melatonin out of serotonin.  Interestingly, one paper I came across noted that the brains of suicide victims had less melatonin in them than those people who had died accidentally.1  The same paper also said that the brains of people with Alzheimer’s disease also had less melatonin in them than similar aged counterparts.  Undoubtedly there are many causes for developing Alzheimer’s disease, but it seems that lack of melatonin production is amongst them.  And then there is low melatonin levels associated with cancer.  Multiple studies have been done on shift workers showing an increased risk of developing cancers, the first footnoted study results being taken from the huge Nurses’ Health Study2 and the second hypothesises that lighting has become a public health issue and may be the reason for the higher rates of breast and colorectal cancers in the Western world.  This paper is based on the findings of many research papers. 3

For good health we should have a clear circadian rhythm.  When we get up in the morning, our production of melatonin should drop away, and then start rising when it goes dark.  As melatonin levels rise, our body temperature drops and we feel sleepy.  And it seems the cue for all this comes from light falling onto our eyes.

The human circadian pacemaker is exquisitely sensitive to ocular light exposure, even in some people who are otherwise totally blind. 4

The quoted research found that we are especially sensitive to short wavelength light, and that means light at the blue end of the spectrum as opposed to red light. 5 So to suppress melatonin production because it is morning, we need strong light and if it is artificial, it should be blue.  Of course, the fun starts at night when we are supposed to be asleep and producing melatonin like billy-o.

Again, a much studied subject is how much light does it take to disrupt melatonin and does this light have to fall on our eyes?  Without a shadow of doubt, it does not take much light to disturb our melatonin production, especially if that light is blue or green. What is rather more worrying is the question of whether light on our skin, but not our eyes will reduce melatonin.  Usually, in the studies,the light is placed behind the knee, so no light can reach the eyes.  Results are very mixed, with more recent studies saying it has no effect on melatonin production – but one study I found found light behind the knee increased the frequency of REM sleep. 6.  Increased REM sleep is associated with depression.  Another study showed that light behind the knee increased wakefulness.7  The upshot is that any light on us whatsoever reduces sleep quality, even if it does not affect our melatonin.

Another disruptor of melatonin production is aging.  As we age and get more decrepit, the lenses in our eyes lose clarity and let in less short wavelength  light with the result that we get worse at suppressing melatonin during the day.

Significantly reduced melatonin suppression was noted in the elderly subjects following exposure to short wavelength light compared to the young subjects.8

The footnoted study posits that one of the possible causes of disturbed circadian rhythms and sleep in the elderly may be impaired light input into their circadian body clock.  So with worsening eye condition, melatonin levels no longer fall in daylight as they should, thereby messing up the sleep/wake cycle.

Key points:

  • Sleep in a dark room.
  • Should we need to get up in the middle of the night, do not turn on the light.
  • If using an electric alarm, avoid having it shine into the face at night.
  • If we need to be awake, for instance if in a different time zone, get into bright light to turn down melatonin.
  • To become properly sleepy at night, avoid bright lights, especially blue or green ones.
  • If crossing time zones, taking a high quality melatonin supplement in the evening will help change our body clock to the new time.
  • If doing shift work, in the night time, try to avoid bright lights.  It may be a matter of doing some research and trying to enlighten the employer.
  • As we age, we need to do all we can to keep our eyes healthy.  During the day, using a bright light such as those used by sufferers of SAD, particularly in the winter months, will help to keep our body clocks in tune with the day/night cycle.
  1. Daily variation in the concentration of melatonin and 5-methoxytryptophol in the human pineal gland: effect of age and Alzheimer’s disease.  Skene DJ et al.  Brain Research, 528 (1990) 170-174. []
  2. Night shift work and risk of colorectal cancer in the Nurses’ Health study.  Schernhammer Es.  JNC I J Natl Cancer Inst (2003) 95 (11):825-828. []
  3. Lighting for the human circadian clock; recent research indicates that lighting has become a public health issue.  Pauley SM.  Medical hypotheses.  Vol 63 Issue 4. 2004. p588-596. []
  4. High sensitivity of the human circadian melatonin rhythm to re setting by short wavelength light.  Lockley SW, Brainard GC, Czeilser CA.  J Clin Endocrinol Metab 2003 Sep:88(9):4502-5. Abstr []
  5. The influence of different wavelengths of light on human biological rhythms.  Morita T, Tokura H.  Appl human sci 1998 May: 17(3):91-6.  Abst []
  6. Enhancement of REM sleep during extraocular light -exposure in humans.  Murphy PJ, Campbell SS.  American journ of physiology regulatory, integrative and comparative physiology 2001 cols 280, issue 6 P R1606-R1612. Abst []
  7. Extraocular light exposure does not phase shift saliva melatonin rhythms in sleeping subjects.  Lushington K et al.  Journ of biol rhythms. 2002. Vol 17 issue 4, p377-386.  Abst []
  8. Light-induced melatonin suppression: age-related reduction in response to short wavelength light.  Herljevic M, Middleton B, Thapan D, Skene D J.  Exp Gerontol.  2005 Mar; 40(3): 237-42 []

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