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Caffeine delays your biological clock


Woman asleep with coffee cup

Credit: iStock

The phrase”psychoactive drug” probably brings to mind things like marijuana, LSD, and a host of alarmingly prevalent and disastrous chemical nasties. As concerning as these substances may be there is however, a substance that is the world’s most popular psychoactive drug and yet it may not be thought of as a psychoactive drug. Has your mind ticked across “caffeine” yet, because that is the substance we are talking about. Caffeine is a staple in most diets around the world and yet it has undeniable psychoactive effects and now a new study has shown that one of those effects is that it alters your biological clock.

The new study involved subjects who were tested under four conditions. Those conditions involved different circumstances at night including; being exposed to low light and taking a placebo pill, being exposed to low light and taking a 200mg caffeine pill (equivalent to 1-2 cups of espresso coffee), bright light and a placebo, or bright light and caffeine.

Saliva samples of the subjects were tested periodically during the study for the hormone melatonin, a hormone produced by the pineal gland as directed by the body’s circadian rhythm. A rise in melatonin levels signal the onset of biological nighttime and decrease signals biological daytime.

So it is not simply that caffeine stimulates you and therefore keeps you awake, it actually resets your biological clock making you go to sleep later and then wake later.

Those taking the caffeine pill in low light had a 40-minute delay in their onset of biological night. This was about half the effect of three hours exposure to bright light. Bright light alone delayed the biological clock by about 85 minutes but bright light with caffeine added delayed things by 105 minutes. The researchers believe there was probably ceiling effect explaining why the combined effect of caffeine and light did not simply equate to adding the effects of the two together.

The researchers also found that caffeine blocks cell receptors for the neurotransmitter adenosine which is partly why it has these effects.

So it is not simply that caffeine stimulates you and therefore keeps you awake, it actually resets your biological clock making you go to sleep later and then wake later. The researchers think that this has implications for dealing with “jet-lag” and may offer insight into some sleep disorders. It also means that after dinner macchiato or affogato may not be such a good idea.



 

Terry Robson

Terry Robson is the Editor-in-Chief of WellBeing and the Editor of EatWell.