Disruption of biorhythms

In some respects biorhythms are like stress in that they developed in response to situations we found ourselves in hundreds of thousands of years ago.  Like stress, our body’s in built and inherited biorhythms are outdated in a modern world that has a 24 hour culture. 

In normal circumstances our in-built body clocks are not in conflict with external zeitgebers.  The daily pattern of life, waking in the morning at or around sunrise, working through the day when our metabolism, body temperature etc. are at their peak and going to sleep at night when it gets dark, causes no disruption.  However, given modern life there are situations now when our internal clocks do come into conflict with external cues, such as dark/light.  The two most obvious examples are shift work when we operate on a rotating schedule of hours and jet lag when we travel across time zones either east to west or west to east.

Jet lag

Jet lag or desynchronosis is caused by the body’s internal body clock being out of step with external cues.  This results in a number of symptoms including fatigue, insomnia, anxiety, constipation (or diarrhoea), dehydration and increased susceptibility to illness. 

Suppose you leave London Heathrow at 6pm (GMT).  The flight to New York JFK will take about six hours.  However, because time on the east coast of America is five hours behind you will arrive at 5pm local time.  However, your body clock assumes that its midnight since the flight has taken six hours.  As a result your internal clock is ready for bed, your temperature is starting to fall and your metabolic rate is slowing.  External cues however, are telling you something quite different, its still light, people are still shopping, the roads are still busy etc.  To overcome this conflict between internal and external effects is not difficult.  Provided you keep yourself well stimulated for the next five or six hours you should be able to stay awake ‘til 11pm local time (4am body clock time) and adapt to the new time zone.

But, suppose you leave JFK airport in New York at 12 noon (Eastern standard Time) heading for London Heathrow.  The flight is six hours.  You arrive in London at 6pm (New York Time) but this is 11pm GMT (London time).  Are you with me so far?  Your endogenous clock has just lost five hours!  Your body clock still thinking it’s only 6pm, is not ready for bed.  Your body temperature, metabolism etc. is still at its peak.  To adapt to the new time setting you must now go to bed!  This is not so easy as going east to west.  Going to sleep when you are wide awake is not as easy as staying awake when you’re tired.  As a result flying east to west is more troublesome and takes longer to adapt.

Research evidence provided by Schwartz et al (1995) supports this theory.  They studied the results of baseball games involving teams on the west and east coasts of America.  The time difference here is three hours.  They found that east coast teams travelling to play away games on the west coast won significantly more games that west coast teams travelling to the east.

A bit of biology:

Research suggests we have two distinct time keeping centres in the brain, one sticks to the body’s internal clock and the other is influenced more by external cues such a levels of light.  Normally these two centres are synchronised but during jet lag desynchronisation occurs.  Dr Horacio de la Iglesia (2004) exposed rats to artificial days and nights lasting eleven hours rather than the usual twelve.  Gradually over a period of days the rats started to exhibit daytime behaviour at night. 

Dr de la Iglesia discovered that their SCNs contained two proteins; Perl and Bmall and also that the SCN could be seen as having a top half and a bottom half. Now for the technical bit.

During a normal day the rats would have the protein Perl in both halves of the SCN whereas at night both halve would contain the protein Bmall:

However, when the rats became desynchronised and started exhibiting daytime behaviour at night Perl was found in the top half and Bmall in the bottom half. 

The bottom half of the SCN appears to stick to the body’s internal 24 hour cycle whereas the top half responds to external cues or zeitgebers such as light. 

Using melatonin to reset the body clock

Apparently melatonin is used by American military pilots to adapt to differing time zones.  Melatonin is the chemical secreted at night and enables us to switch off the RAS (that keeps us awake during the day).  Taken just prior to bedtime in the new time zone, melatonin has been shown to be effective in allowing sufferers of jet lag to get to sleep sooner than their body clock would normally allow.  At present the EU has not given melatonin a licence in Europe.

Using fasting to reset the body clock

Recent research has also shown that social factor can play a role in resetting biological rhythms and alleviate some of the symptoms of jet lag.  For example a period of fasting before travel followed by eating at times relevant to the new time zone.  Apparently food is very good at altering biological rhythms (Fuller et al 2008)

Saper (2008) suggests that as well as the main ‘master’ clock in the SCN there is also a ‘feeding clock’ which depends on food intake.  In mice, this feeding clock seems to over-ride the master clock and keeps them awake until food has been found. 

So if we are flying from London to New York and need to adjust to the new time zone by staying awake longer than the master clock would expect we need to starve ourselves before and during the flight and then eat when we land.  This way we can postpone the master clocks drive to get us to sleep.  Saper and his team recommend fasting for 16 hours before eating!

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