Seasonal clocks and our biological clocks have influenced life since the beginning of time. We have just passed the summer solstice in the Northern Hemisphere, and the winter solstice in the Southern Hemisphere, and Stonehenge continues to draw people on an annual pilgrimage as it has been doing for the past 5000 years.
As with most things in life, timing is everything
The 24 hour cycle between daylight and darkness has programmed our genes and cells to respond in a timeless manner. In an ideal environment , this should be how we all operate. But human behaviour has changed and so has our exposure -time to artificial lighting.
Shift work and jet lag (not so much at the moment!) disrupt circadian rhythm and genetics may predispose sensitive individuals to gastrointestinal issues as well as risks for cardiometabolic issues. When it comes to shift work, it is interesting to note that it takes a shorter adjustment period to night shift, but a much longer period to re-establish a daytime routine.
Many electronic devices emit monochromatic blue light which can affect melatonin production. Melatonin synthesis takes place overnight, in darkness. Reduced melatonin impairs next-morning alertness and impacts many metabolic processes including the antioxidant ability to scavenge free radicals which may damage DNA. Melatonin deficiency has been linked to many disorders such as Type 2 Diabetes risk and weight gain.
Sleep deprivation can lead to abnormal glucose regulation as well as endocrine disruption. TSH levels (Thyroid-Stimulating Hormone) may be impaired and overnight cortisol secretion increased. The circadian rhythm of cortisol secretion has a wave-like pattern. Cortisol levels rise approximately 2-3 hours after falling asleep and continue to rise into the early morning and early waking hours. The peak in cortisol is about 9am.; as the day continue, levels slowly decline allowing the body to relax and prepare for sleep. The initiation of sleep is controlled by the HPA (Hypothalamus- Pituitary-Adrenal) axis. Sleep disorders, anxiety and chronic stress disrupt these carefully timed pathways and lead to an ongoing negative cycle that needs to be dealt with.
Sleep deprivation can lead to abnormal glucose regulation as well as endocrine disruption. Weight gain and cravings for high fat/high carbohydrates have been found to have a high prevalence in disrupted sleep patterns and sleep disorders.
Daily exposure to natural light is only 88% in many cities , which amounts to 1-3 hours per day. Vitamin D, an essential hormone and vitamin necessary for many functions, is manufactured in our skin using sunlight. Vitamin D also plays a role in clock gene transcription.
CLOCK 3111 T>C (Circadian Locomotor Output Cycles Kaput) genes can determine whether you are a 'morning person', or a 'night owl'. This can be referred to as your Chronotype
These internal time-keeping systems regulate energy balance, eating behaviour and body weight regulation. Individuals homozygous for the C allele (CC genotype), have shown a preference for for eating later at night, eating more at night, shorter sleep cycles and higher ghrelin levels (hunger hormone), as well as a preference for high protein foods and processed foods.
For these genotypes exercise is an important tool for improving sleep quality and weight management. Wearing blue-blocking glasses in the evening and establishing a regular bedtime routine is important. Short, afternoon 'power naps' may help CC genotypes or 'night owls', reduce their sleep deficit and reduce their inflammatory response.
Eating most of their calories during the day and finishing the last meal by 6.00 pm, had been beneficial for weight management. Time-restricted feeding (Intermittent Fasting) may work well for CLOCK CC genotypes.
No matter what your genes may be, living in synchronicity within the natural order of cycles and seasons has determined life on earth for all living beings and will continue to do so.
Enjoy the gifts of nature as much as possible and learn to make the most of these natural time-keepers.