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Episode 9: Time and Our Bodies: Chronobiology

Time and Our Bodies: Chronobiology

What is Chronobiology?

Chronobiology is the biology of time and internal biological clocks. Biological clocks range from oscillations found in nerve cells on the millisecond scale to oscillations in minutes, hours, days, and years. Chronobiology is a field of biology that examines timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms.

The study of chronobiology started with plants and with floral clocks - plants that show flowering at certain times of day.

Recently scientists have discovered clock genes - how they work - and how we can become uncoupled from this time reference point and what that means for health. In 2017 the Nobel prize was given to the researchers Hall, Rosbash and Young for this research.

The master clock in the SCN - set by light coming in from the eye. The suprachiasmatic nucleus (SCN) of the hypothalamus is the principal circadian pacemaker in the mammalian brain and, as such, it generates circadian rhythms in rest and activity, core body temperature, neuroendocrine function, autonomic function, memory and psychomotor performance. CLOCK is a gene encoding a basic helix-loop-helix-PAS transcription factor that is believed to affect both the persistence and period of circadian rhythms.

Dopamine regulates and modulates circadian biology - hence mood and subjective experience of time. Melatonin - the darkness hormone - entrains the clock we have in our bodies.

Blood panels will give you a hormone profile, however subjective feelings of wellness are also a good indicator of how your circadian rhythm is doing - are you constantly tired? Do you get a lot of infections? Are you getting enough sleep? Are you sleeping at the right time? This is direct feedback from your body that you might want to look at your circadian cycles.

A zeitgeber is any external or environmental cue that entrains or synchronizes an organism's biological rhythms to the Earth's 24-hour light/dark cycle and 12-month cycle. Your circadian rhythm is cued by your environment - so you need to set your clock by your environment - eat the food from that area - also in season. Be outside for at least 2 hours a day. Ground in the environment.

Gut bacteria regulate time in our bodies - there are peripheral clocks in our bodies. The gut microbiota composition is influenced by host circadian rhythms, and in turn, gut microbes are essential for the regulation of host circadian pathways.

The immune system is yoked to peripheral clocks. Sarah talks about the lecture ‘Building Circadian Medicine in a Pediatric Hospital’ by John Hogenesh, PhD. In this talk the researcher describes the ward rounds in hospitals - the timing of drug administration had a significant effect on patient outcomes.

Morning lark or night owl? Which one are you? Early chronotypes (“morning larks”) rise early and are most active in the morning, but feel tired late in the afternoon or early evening. Late chronotypes (“night owls”) are tired during the morning, but feel awake in the evening. Is this just a habit?

Best time for cognitive task - is in the morning between 9-11am.

What about coffee? Bulletproof coffee has coconut oil and butter in it. Have coffee early in the day so it doesn’t interfere with sleep.

Best time to eat: Breakfast like a king, lunch like a price, dinner like a pauper

Best time to have sex: male sex hormone, testosterone, peaks in the late evening and again in the early morning. (There is also a minor peak in the early afternoon.) Oestrogen, the female sex hormone, is at the lowest level in women in the morning and then rises gradually during the day to peak at around at 10pm.

Best time to have a vaccination: Birmingham University researchers reported last year that older patients vaccinated against the influenza virus in the morning rather than the afternoon produce more antibodies against the seasonal virus strains. If flu vaccinations were administered ‘morning-only’, it could save 2,400 deaths each year, the researchers claim.

Top Tips from this week's episode:

Take care of your circadian clock!

  • If you have chronic illness - you most probably have an issue with your body clock - so take steps to rectify it

  • Get as much sunlight in the day as possible

  • Minimise blue light exposure especially after dark

  • Get good deep sleep - around one hour every night (use a sleep tracker to check)

  • Get 7-8 hours sleep every night

  • Go to bed at the same time every night as much as possible

  • Do intermittent fasting by eating dinner early and not snacking at night


Hospital study Sarah refers to:

Morning vaccination enhances antibody response over afternoon vaccination: A cluster-randomised trial

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