
How your circadian rhythms affect your physical and mental performance
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See how circadian rhythms affect your cognitive abilities, your physiology, and the way foods act on your body
Circadian rhythms occur with a periodicity that is synchronized with the rotation of the Earth on its axis and that continue in the absence of external stimuli. In mammals, they regulate the physical, mental and behavioral changes that occur during a 24-hour cycle.
Just as we schedule our day to carry out different activities, our body carries out countless activities during the 24-hour period, hormones, enzymes that work on different physiological needs, genes that are activated or mitigated, in short, thousands of activities within the organism that functions according to a daily schedule that is repeated every day.
When we mention circadian rhythms, the first thing that comes to mind is the sleep period since our body requires approximately 1/3 of those 24 hours to sleep.
It turns out that every organ in our body – the liver, the lungs, and even the skin – has its own daily circadian rhythms. Today I bring you the highlights of Dr. Satchidananda Panda's discussion with Dr. Rhonda Patrick on circadian science regarding the proper timing of exercise, the biology of melatonin, and peak cognition throughout the day .
Circadian rhythms have been found to be present even at the cellular level . Circadian rhythms are controlled by an endogenous oscillator, the circadian clock. The circadian clock allows organisms to anticipate rhythmic changes in the environment and to modify their physiological state accordingly, which gives them an adaptive advantage. [1] This refers to mammals, but specifically to humans and their internal organs.
Different chronotypes: which flock do you belong to?
Chronotype is the term used to refer to a person's predisposition to be more efficient in their activities in the morning or afternoon. This means that there are people who do better with an early night sleep because they function better in the early morning hours (“lark” chronotype), while other people feel that they function better in the evening hours and prefer to go to sleep late (“night owl” chronotype). There are also those in between, since the majority of the population belongs to the group (“hummingbird” chronotype), who function better during the normally established hours of activity: 9am-5pm and can easily go to sleep at 10pm or 11pm.
What would then be your peak cognitive function?
According to Dr. Satchidananda Panda's extensive research, circadian rhythms are found in all components of attention, both in what he calls tonic alertness (general alertness) and phasic alertness (moment-to-moment alertness), as well as in selective attention (ability to ignore irrelevant information in a task) and sustained attention (ability to focus on a task for a long period of time). And concludes that our attention improves during the day, while it reaches its lowest levels at night and in the early hours of the morning. [2]
However, depending on your chronotype, if you identify with the flock of larks, you may peak your cognitive function in the morning hours, compared to “night owls” who have significantly more daytime sleepiness compared to early chronotypes and perform worse in the morning on all cognitive and physical measures. In these cases, what caffeine does is wake up our brains, but it doesn’t allow us to think more clearly, says Dr. Panda.
It is important to respect the number of hours we slept the night before if we want to be fully awake and fully functional the next day.
Mood disorders associated with altered circadian rhythms: seasonal depression, bipolarity, depression manifested in body temperature, hormonal secretion, cortisol, melatonin, blood pressure, sleep-wake cycles.
Disruptions in the circadian rhythm can cause deterioration in health and daily performance
According to studies by Dr. Russell Foster and others [3] , the impact of sleep and circadian rhythm disturbances caused by social jet lag (the time difference between the midpoint of sleep on workdays and on days off arising from the discrepancy between an individual's own biological rhythm and the daily schedule determined by social restrictions), and changes in work shifts illustrate the severe health consequences of working against one's biological time.
Emotional responses |
Cognitive responses |
Somatic responses |
· Exhaustion · Increased irritability · Sudden mood swings · Depressed mood · Frustration · Rage · Increased impulsivity · Decreased motor skills · Increased use of stimulants · Increased use of sedatives · Use/misuse of alcohol |
· Decreased concentration · Decreased performance · Decreased attention · Decreased memory · Reduction in the ability to remember events · Reduction in multitasking ability · Reduction in decision-making capacity · Reduction of creativity · Reduction in productivity · Reduction of socialization · Reduction in communication |
· Drowsiness · Micro naps · Involuntary sleep · Bodily sensations of pain · Body sensations of cold · Cardiovascular disease · Risk of cancer · Metabolic abnormalities · Overweight · Risk of type 2 diabetes · Immune weakening · HPA (hypothalamic-pituitary-adrenal) axis disorders |
Why is it important to seek sunlight in the morning and avoid bright lights at night?
Dr. Satchidananda Panda points out that a very small percentage of people are actually considered “night owls” since people who consider themselves to be within this chronotype often tend to stay up late due to habits other than their genetic predisposition. What happens is that nocturnal activities such as watching television, using the computer (whose blue light inhibits sleep) or drinking stimulating beverages such as coffee, tea or chocolate in the afternoon definitely prolong the hours of wakefulness in the body, but once the stimulants are eliminated, it is very possible that many of these people adjust to a schedule more in line with daylight hours and go to sleep between 10 and 11 p.m. and can rest easily for 7-8 hours.
Because the hormone melatonin is activated in the dark and induces sleep, Dr. Panda indicates that it is a good idea to let it activate naturally so that we can fall asleep. For that to happen, we must release the brake, which in this case is the blue light, and an important action is to reduce the power of the night lights to inform our body that it is time to sleep.
On the contrary, in the morning it is ideal to receive daylight (it does not have to be direct sunlight) and one hour and thirty minutes of light is recommended in order to “turn off” the production of melatonin and, conversely, to activate light, which affects mood, induces motivation and cognition through a pathway that connects the photosensitive ganglion cells that express melanopsin with the perihabenular nucleus. In simpler words, exposure to light modulates our mood like an antidepressant, motivating us, making us happier and preparing us for all our functions, especially our cognitive ones.
There is a connection between melatonin and insulin secretion that could guide us as to the ideal time to eat.
It was only relatively recently (2009) that this link between melatonin and glucose was discovered (people with high blood glucose had a mutation in the melatonin receptor gene) and this is because, just as melatonin makes our brain sleep, it does the same with our pancreas. This means that melatonin makes the cells that produce insulin respond less to glucose and do not produce as much insulin as they normally would when we consume a food high in carbohydrate or glucose. The general consensus is that it is not advisable to eat close to bedtime (try to do it at least three hours before) and when getting up, wait at least 1-2 hours before eating, so that blood sugar levels are balanced.
It's awfully easy to disrupt our circadian rhythms
By continuing to work beyond office hours and continuing to work two or three hours longer at home, we are shifting the natural sleep schedule, and this is a common practice these days. If this is done once a week, which in annual terms would correspond to 50 days, the person is considered a “multi-shift worker.”
The problem is that a person who goes to bed too late or gets up too early often has to rely on stimulant drinks , food or light to make up for lost sleep, which disrupts normal circadian rhythms and causes symptoms to be experienced as when switching to another time zone.
In addition, the body will try, in its own way, to get back on track. To make up for two hours of lost sleep, it takes about 2 days to readjust the body and one day, as is often the case on a transatlantic flight, at least 3 days to align our daily habits with our internal clock.
How to balance your circadian rhythm
- Adapting our bedroom so that it is completely dark at night so that we can naturally produce the hormone melatonin. Sometimes earplugs and an eye mask may be required so that we can at least get those extra 1-2 hours of sleep during the day that our body so desperately needs.
- A nap helps improve your mood, cognitive performance, lethargy and fatigue. If you have the opportunity to choose between a nap and a coffee, the choice is definitely the nap.
- To avoid drowsiness after lunch, it is recommended to try to have lunch in a well-lit place, and if it is outdoors, even better.
Circadian rhythms and time-restricted feeding
Unlike intermittent fasting, which involves calorie restriction, time-restricted feeding allows a person to eat as much as they want during their feeding window. Time-restricted feeding aligns feeding and fasting cycles with the human body's innate 24-hour circadian system, and human experiments have already proven this.
Circadian rhythms help our body repair and rejuvenate itself. Unlike a car engine that can be started and accelerated from 0-60 km in 5 seconds at any time, the human body simply cannot. The human body has to prepare itself: during the 7-8 hours of sleep we need, the body takes advantage of this to restore itself, eliminate toxins, transport nutrients, strengthen neural connections and more.
Just as the brain disconnects from any information for 7-8 hours, every cell in our body needs to do the same , because external sensory stimuli influence all of our organs. One of those sensory stimuli is food, because when we eat, the levels of many hormones in our body change rapidly, even the levels of certain nutrients in our food change. That is why it is crucial to stop eating at least 3 hours before going to sleep.
But if the brain only needs 7-8 hours of sleep, why do we need to fast for 12, 14 or more hours? Dr. Panda points out that when we eat, our stomach needs about 5 hours to digest the food. After those 5 hours, the intestine must require several hours to absorb nutrients or transport others to the liver or other parts. This means that if you finish your meal at 6pm, your stomach has to work until 11pm or later, so your body does not have time to regenerate itself.
When counting the time you are fasting, you have to subtract at least 5 hours from that total and thus you will obtain the true number of hours that your body is resting from food, regenerating and rejuvenating naturally. When you only consume food during a 8-10 hour window and fast for 14-16 hours, that translates to just 8 hours of true fasting. Many experiments conducted by Dr. Panda corroborate that the time(s) in the day when we consume food definitely affects our circadian rhythms. [4]
Simply by reducing your feeding window or eating for a set number of hours and avoiding all food for at least 14-16 hours you can adjust your behavior, physiology and metabolism for optimal health, says Dr. Panda.
Exercise and physical activity in synchrony with the circadian rhythm
According to studies, it has been detected that optimal athletic performance peaks after midday,
“In athletes, it is known that endurance performance is lower in the early morning and late evening compared to the afternoon, and that maximal fat oxidation and max fat (exercise intensity inducing maximal fat oxidation) are higher in the afternoon compared to the morning, whether in non-athlete male students, in obese individuals and also untrained normal weight individuals, or in endurance-trained athletes. The difference is explained by the higher body temperature, greater neuronal activation and contractile properties of skeletal muscle, as well as the higher concentration of plasma catecholamines in response to exercise in the afternoon compared to morning and evening…
…The peak of cardiovascular endurance performance is in the afternoon, which normally coincides with the highest internal body temperature reached during the day. This temperature increases energy metabolism, improves muscle flexibility, and facilitates the formation of actin-myosin cross-bridges. In addition, the peak of catecholamines induced by exercise is greater in the afternoon than in the morning. The release of catecholamines promotes an increase in lipolysis (movement of stored fat) in both skeletal muscle and adipose tissue, raising the content of fatty acids in plasma and explaining the higher rates of fat oxidation observed in the afternoon.” [5]
However, according to chronotype, morning people demonstrate better athletic performance in the morning compared to other chronotypes, specifically, night owls. [6]
Another experiment in Sweden showed that in people with type 2 diabetes, exercising in the morning with high-intensity interval training (HIIT) actually increased their blood sugar, while doing the same type of training in the afternoon kept their blood sugar levels stable. [7] This shows that our pancreas has a clock and means that the pancreas produces more insulin in the morning or at least in the first half of the day, while in the second half of the day, and in the absence of melatonin, it does not produce as much insulin as in the morning.
Final tips from Dr. Satchidananda Panda to keep in mind:
- Try to sleep 7-8 hours in bed
- When you wake up, wait at least 1 or 2 hours before consuming your first calorie.
- Feed within a well-planned feeding window of 6, 8 or 10 hours, but no more than 12 hours.
- Do physical activity outdoors in daylight for more than 30 minutes.
- Avoid all food and bright lights 2-3 hours before going to bed.
If you would like to listen to the full talk by Dr. Satchidananda Panda and Dr. Rhonda Patrick, here is the link: https://youtu.be/MWngLVQg2Os
References
[1] Harmer, Stacey L., Satchidananda Panda, and Steve A. Kay. “Molecular bases of circadian rhythms.” Annual review of cell and development biology 17.1 (2001): 215-253
[2] Valdez, Pablo. “Focus: Attention Science: Circadian Rhythms in Attention.” The Yale Journal of biology and medicine 92.1 (2019): 81
[3] Foster, Russell, G., et al.” “Sleep and circadian rhythm disruption in social jetlag and mental illness.” Progress in molecular biology and translational science 119 (2013): 325-346.
[4] Hatori, Megumi and Satchidananda Panda. “Response of peripherial rhytms ot the timing of food intake.” Methods in enzymology 552(2015) 145-161.
[5] Ramírez-Maldonado, Mauricio et al. “Caffeine increases maximal fat oxidation during a graded exercise test: is there a diurnal variation?” Journal of the International Society of Sports Nutrition 18.1 (2021): 1-9.
[6] Vitale, Jacopo Antonino, and Andi Weydahl. “Chronotype, physical activity, and sport performance: a systematic review.” Sports Medicine 47.9(2017): 1859-1868.
[7] Saviki, Mladen, et al. “Afternoon exercise is more effective than morning exercise at improving blood glucose levels in individuals with type 2 diabetes: a randomized crossover trial.” Diabetologia 62.2 (2019): 233-237.
2 comments
Al leer tu interesante artículo , me clasifico búho nocturno, espero mejorar mis hábitos antes de dormir , ya que no llego a 7 hrs de sueño …. Muchas gracias
Excelente artículo