By Penelope A. Domogo, MD
Circadian rhythms “refer to the natural fluctuations of bodily processes in plants, animals and microbes along a 24-hour cycle.” (Austin Meadows in Sleep.org). This phrase comes from the Latin “circa diem” meaning “around a day.” These fluctuations follow the sun in a consistent 24 hour cycle so it is like a routine. An example of a circadian rhythm is the sleep-wake cycle of humans and animals. We sleep when night falls and wake with the dawn or when the sun is up. The term for this is “diurnal”- active during the day and asleep at night. As opposed to “nocturnal” which is active during the night and sleeping at daytime such as owls. Plants also have their circadian rhythm and also sleep during nighttime. This is visible in the acacia which folds its leaves at 5pm and opens at daytime. I first learned about this from Dr. Juan Flavier in his book Doctor to the Barrios. Try observing the acacia.
How does this work? Science also has shown that these rhythmic cycles in our body are controlled by biological clocks in every cell which are synchronized by a master clock in the brain. This master clock is called the suprachiasmatic nucleus (SCN), found in the hypothalamus of the brain. This master clock is highly sensitive to light- meaning light is its stimulus to send signals to the different body clocks to regulate our activities. For example, when the sun sets and it becomes dark, the SCN directs the body to release the hormone “melatonin” and this chemical makes us sleepy. It is our natural sleeping potion. When the sun rises in the morning, our biological clock directs our body to suppress melatonin production. Stop muna. Instead, this same clock directs our body to release the hormone “cortisol” in the morning and this chemical energizes us. Wow, isn’t this just amazing! Our body systems are at work inspite of our consciousness. Research also has found out that melatonin production is best in complete darkness and when we are exposed to sunlight during the day especially in early morning. So farmers who live according to the dictates of the sun have the best sleep.
With light as the most important stimulus of our biological clock, it is no wonder that our circadian rhythms are in sync with the day-night cycle. Temperature, exercise and work hours, lifestyle also affect our body clock. We see the chaotic effects of global warming in our plants- our persimmon is fruiting at this time when it is supposed to be in June. The warm temperature also makes some infectious diseases like dengue thrive in supposedly cold places like Sagada.
This sleep-wake cycle is connected to a lot of other processes in the body- like digestion and metabolism. Since we are diurnal creatures, it follows that our eating patterns occur during the day. This is in sync with the production and release of hormones necessary for proper digestion and elimination. So eating late at night stresses your systems. How is this? As darkness falls, your circadian rhythm dictates that you sleep. And when you sleep, it is not only your eyes that will rest. Your brain activity slows down, your heart rate slows down, your body temperature lowers because your metabolism slows down. Meaning all your body systems rest when you sleep. But if you ate late at night or you ate too much, then your digestive system still has work to do. But then it is also sleepy so imagine na lang a sleepy stomach trying to blend the rich food that you ate. The effect is that both your sleep and your digestive system are disturbed. So you don’t get a good rest and your food is not digested well. Double jeopardy. So it is advised that we eat at least three hours before sleeping and no midnight snacks.
We need a good rest at night so we can regain the energy needed for the next day. Compare it to recharging empty battery of your cellphone. Moreover, we need this rest to repair and heal and regenerate whatever needs to be healed in our cells.
Newborns develop their circadian rhythm when they are a few months old that’s why sometimes they are awake at night and asleep during the day. They only begin to release melatonin when they are about three months old and cortisol develops from 2 to 9 months old. As we age, our circadian rhythms should be consistent, if we practice healthy habits that are in sync with day-night rhythms and seasonal changes. Older adults, though, experience changes in their circadian rhythms- sleeping earlier that usual and waking up earlier at 2 or 3 am. This is part of aging and should be okay as long as you still feel energized during the day.
The following can throw our internal clocks off track and disturb our circadian rhythm:
1. Work shifts that go against the natural light and dark times, like night shifts.
2. Work shifts with erratic hours
3. Travel that spans one or more different time zones – causing jet lag.
4. Poor sleep habits like lack of sleep schedule, eating and/or drinking late at night, watching screens too close to bedtime.
Long-term disruption of our circadian rhythm leads to disruption of our natural sleep patterns and this can impact on all our organ systems. Further, it can lead to a host of health problems like obesity, diabetes and mental health issues. This is why night shifters in call centers develop health issues after some time.
Our bodies, though, can adjust and reset and get it back on track with the following measures:
1. Stick to a routine. Those on night shift should consider other work options.
2. Spend time outdoors during daytime.
3. Get enough physical exercise daily- 20-30 minutes at least.
4. Sleep in an environment that promotes rest- turn off the lights to ne natural.
5. Avoid alcohol, caffeine and nicotine in the evening- for those who are sensitive to these substances. I know some people need coffee or alcohol to sleep.
6. Turn off the screen well before bedtime and instead listen to soft slow music or read something light or meditate. Blue light from electronic gadgets can suppress melatonin, disrupting sleep.
7. Do not nap late in the afternoon.
8. Eat fruit vegetables and legumes at supper to slow you down.
There, our Creator built in our bodies and in all living things around us, amazing internal clocks that tick to the rhythm of the universe so that we will live healthy and well. Let us take care of them.***
“You made the moon to mark the seasons; the sun knows when to set. You bring darkness, it becomes night and all the beasts of the forest prowl.” Psalm 104:19-20
