How do plants 'tell time' for circadian rhythms based on a ~24 cycle?

How do plants 'tell time' for circadian rhythms based on a ~24 cycle?

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I've read that many plants have some sort of circadian rhythm where they perform a certain action on a cycle of about 24 hours, like the mimosa plant opening and closing its leaves. Obviously, this is done in order to synchronize with the sun, but many such plants continue to perform these actions even when left in constant darkness or light. It follows that this is the result of some sort of biochemical pathway, but whatever internal 'clock' is used is also independent of temperature.

How can these plants perform certain actions every 24 hours at different temperatures when the chemical reactions most biochemical pathways use are temperature dependent?

It would seem like the length of the cycle should vary widely according to the temperature as it affected the reactions involved, but instead it stays at a very constant length very close to 24 hours. How can this be?

(This is in my textbook, but unfortunately the book doesn't cite any studies. I would greatly appreciate it if anyone could help me find one to link to so I can improve the question. :)

The short answer is that it is because the reaction chains dispensing time and enzymes doing those reactions have evolved to negate the impact of environmental factors.

The true answer is that the plant clocks do gradually lose sync with 24h cycle when put in stable lighting conditions and move to some more-less random characteristic frequency of their molecular clock which is quite likely dependent on environment (still it is obviously close to 24h) -- the sad truth is that every clock needs syncing to work properly.

Plant Biology in the Fourth Dimension 1

The nature of time has long been an obsession for philosophers, scientists, and laymen. This nearly universal interest in time is encapsulated by the fact that the quotation “Time is nature’s way of keeping everything from happening at once” has been attributed to both Woody Allen and Albert Einstein! Although some argue that time is an illusion, ongoing work has revealed that most organisms possess an internal oscillator, the circadian clock, which has a pervasive influence on growth, development, and responses to the environment. Studies of circadian rhythms in plants reveal that because everything doesn’t happen at once, plants have evolved sophisticated mechanisms to partition physiological processes so that they occur at the most advantageous times, both on seasonal and daily scales.

Dr. R’s Fast Facts Summary

Light exposure

  • Blue light is rich in daylight
    • Humans have what is called Melanopsin which senses blue light and helps to set our circadian rhythm

    How to get better sleep

    What is time restricted eating?

    • Eating all meals within a specified window of time each day, giving your body the opportunity to rest overnight, regenerate, and heal
    • Also referred to as intermittent fasting

    Intermittent Fasting Defined

    • 8-10 hour eating window (16-14 hour of fasting) is doable for most people
    • Try not to eat 2-3 hrs before bedtime
      • During this time, melatonin begins to rise which can slow down the function of the pancreas so the pancreas does not produce enough insulin
      • Eating dinner too late stresses our stomach, intestines etc.
      • Better to have an early dinner

      Benefits of Intermittent Fasting (IF)

      • IF has a number of benefits in the treatment of chronic health conditions like diabetes, obesity, digestive issues, heart disease, mental health, etc.
      • People tend to inadvertently reduce their alcohol and sugar intake
      • Optimizes digestion

      When do you see results?

      • 3 months is a good time frame
        • 1st week – is difficult
        • 2nd week – most experience improvements in sleep
        • 6-10 weeks – many experience some weight loss, improvement in blood sugar and blood pressure

        When to exercise?

        • Exercising in the evening has proven to be more beneficial overall, especially for professional athletes and those with diabetes
          • Exercise in the evening to better control blood sugar

          Where to learn more

          In This Episode

          Episode Intro … 00:00:40
          Light Exposure and Health … 00:02:55
          Time-Restricted Feeding & Why It Matters … 00:09:22
          Research on Intermittent Fasting (Human) … 00:13:36
          Intermittent Fasting and Lowering Disease … 00:21:29
          Optimal Fasting Time Window … 00:27:51
          Building an Intermittent Fasting Habit … 00:35:42
          When to Expect Results … 00:41:44
          The Circadian Code … 00:46:42
          Digestive Benefits from Intermittent Fasting … 00:51:07
          Episode Wrap-Up … 00:53:31

          Subscribe for future episodes

          Download this Episode (right click link and ‘Save As’)

          Episode Intro

          Dr. Michael Ruscio, DC: Hi everyone. Welcome to Dr. Ruscio Radio. This is Dr. Ruscio. Today I am here with Satchin Panda and we’re going to be talking about circadian health and time-restricted feeding. Dr. Satchin, I really have to commend the work you are doing.

          He is doing a terrific service for people, in terms of increasing their awareness of how detrimental inappropriate light exposure can be and also eating too late at night. I want to get into some of those details. Thank you so much for coming on the show today.

          Dr. Satchin Panda: Thank you, I’m glad to be here.

          DrMR: Before we get into the topic, tell people about your background. Then we’ll launch into what I’m sure will be a fascinating conversation.

          DrSP: Well, I did my PhD in circadian rhythms. That was looking at how tiny plants tell time with their leaves, harvest sunlight, and then go back to sleep.

          I learned a lot about how the circadian clock works in plants. The fascinating thing is, you can use the same principle of circadian timekeeping in plants (pond scum even), or humans and mice. So I moved to doing research in mice and fruit flies during my postdoctoral training.

          Then, I have been with the Salk Institute for nearly 15 years now, and my lab works on circadian rhythm, specifically how the body keeps track of time and how these clocks of circadian rhythms respond to light, darkness, eating, fasting. We look at how we can combine all of this knowledge from basic science research to prevent, manage, or even treat some of the chronic diseases that affect millions of people.

          DrMR: And we’ve talked a few times in the past on the podcast regarding light exposure and how, specifically, blue light exposure at night is not good for one’s health. Just in case anyone in the audience hasn’t heard about that yet, can you give a short primer on that?

          How Your Circadian Rhythm Helps You Sleep

          How sleepy we feel, also known as our sleep debt, is determined by two factors operating in two different parts of your brain:

          The first factor is sort of obvious. The longer we stay awake, the more sleepy you tend to be. But have you ever noticed that sometimes, despite being awake for so long, that you just can’t fall asleep? Or that sometimes you feel over-tired and you actually start to feel more alert again? That’s because of your circadian rhythm.

          If you try and fall asleep when you haven’t been awake for long or if your circadian rhythm is telling you that you should be awake, you’ll have a hard time sleeping. But if you’ve been awake for a good amount of time and you’re at a point in your circadian rhythm where your body is starting to wind down, you’ll be off like a light.

          That’s why if you want to sleep better it’s so important that you satisfy those two factors.

          Methods Used to Assess Circadian Rhythms in Cognitive Processes in Humans

          Methods in this field are important to separate the influence of homeostatic and circadian factors on physiology and performance. It is also important to identify homeostatic and circadian variations in physiology and cognitive performance without the influence of masking effects produced by changes in the environment, such as lighting, temperature, or by the activity of the person. Three main methods have been used to study circadian rhythms in physiology and cognitive performance of humans: time of day recordings, a constant routine protocol, and a forced desynchronization protocol [18].

          Time of day recordings implies recording performance two or more times during the day, in individuals living in their normal environment. Typically, the recordings are made only during daytime hours, when the person is awake, to not disturb sleep. The few daytime recordings obtained through this type of protocol are insufficient to measure the circadian oscillations throughout the 24 h of the day. Results from these studies are usually highly variable and many studies obtain contradictory results. Due to the high variability of the results obtained with this protocol, larger samples are required to obtain significant differences at different times of day. Therefore, the results of this type of studies are very limited when attempting to draw firm conclusions regarding the circadian rhythms of cognitive processes [18].

          A constant routine protocol implies measuring physiological and cognitive functions at regular intervals (for example, every hour), for at least 24 h. Masking conditions that can modify the circadian rhythms are kept constant, such as ambient temperature, light intensity, motor activity, and caloric consumption [19]. Participants remain awake and in a reclined position, ingest a small snack at regular intervals, and maintain a very low level of motor activity to minimize possible effects of food ingestion and motor activity on the circadian rhythm of core body temperature. This protocol is useful to assess homeostatic and circadian changes in cognitive performance.

          A forced desynchronization protocol requires the participants to adjust their sleep-wake cycle to a period that is outside the entraining range of circadian rhythms (for example, 28 h). In this condition, the core body temperature continues oscillating with a period close to 24 h, and physiological and cognitive functions can be recorded while the individual is awake, at different phases of the circadian rhythm of the core body temperature [20]. This protocol permits the assessment of homeostatic and circadian changes in cognitive performance [21]. The last two protocols, constant routine and the forced desynchronization protocols, offer suitable controls for the variables that can mask the circadian rhythm, therefore the use of these protocols shows similar results about circadian rhythms in performance [18]. Both protocols allow the recording of circadian rhythms in physiological variables and cognitive performance throughout the 24 h of the day. Results obtained with these two protocols show circadian rhythms in physiology and cognitive performance in each individual recorded, so that significant results can be obtained even with small samples. For these reasons, this review includes mainly results using these two protocols.

          The type of task is also very important to analyze circadian rhythms in specific cognitive processes. To assess human circadian rhythms in cognitive processes, performance is measured several times during the day, this may induce learning or fatigue effects. Tasks appropriate for this type of research should produce little or negligible effects on learning or fatigue, or the measurement conditions must be appropriate to minimize these effects. Very simple tasks may be inappropriate to assess specific cognitive processes. Some of these tasks require the participants to only respond to infrequent stimuli with long intervals between them. Continuous performance tasks, that require frequent and continuous responses, may allow the assessment of specific cognitive abilities [22]. On the other hand, exceedingly complex tasks may include multiple cognitive abilities, and separating the contribution of specific cognitive processes from the execution of the test may be very difficult [23]. Many neuropsychological tests suitable to the analysis of specific cognitive processes, cannot be used repeatedly at very short intervals, because the person may improve performance through learning. It is important to select tests appropriate for the study of human circadian rhythms, to design tasks that may accurately grasp specific components of cognitive processes, or devise other protocols suitable for the analysis of these rhythms. Cognitive performance may be influenced by other factors, such as motivation or emotion. Generally, motivational or emotional factors are kept constant and at a reduced level in these experiments. It is possible that these conditions may induce masking effects in natural environmental conditions, thus affecting the recording of circadian rhythms. More research is needed to study the possible effects of motivational or emotional factors on circadian rhythms: do these conditions induce only transitory masking effects? Are these conditions capable of modulating the amplitude, period or phase of the circadian rhythms in cognitive processes?


          It is apparent to even the most casual observer that plant physiology is strongly influenced by time: for example, plants generally fix carbon during the day but are carbon consumers at night, and plant reproduction is strongly tied to the seasons. Although these changes in physiology are clearly linked to changes in the environment, they are also strongly influenced by the plant circadian clock. Studies spanning the past 300 years have revealed that many features of plant physiology are affected by the circadian clock ( McClung, 2006). Clock-influenced processes range from once-in-a-lifetime events such as germination and the transition from vegetative to reproductive growth, to annual events such as the onset of flowering or winter dormancy, to daily processes such as rhythmic movements of petals and leaves and emission of floral fragrance. Ongoing, intensive investigation into clock-regulated processes are revealing that plants are even more sophisticated time keepers than we previously thought, with most or all aspects of plant physiology influenced by the circadian system. The molecular nature of the plant oscillator is now becoming clear, and the development of mathematical models describing this clock are raising hopes that we will someday be able to predict how particular environmental conditions will interact with a given genotype to shape plant growth and development in the real world.

          Circadian Rhythm

          Circadian rhythm (CR) is an endogenous biological rhythm with a period of about 24-hours. CRs are generated within an organism to fine-tune all aspects of physiology and behavior to the varying demands of the 24-hour world. CRs anticipate daily changes in light and dark, temperature, food availability, and even predation and prepare the organism in advance of a changing world so that it is fully adapted. CRs are found in almost all life-forms on the planet, including bacteria. In humans the most obvious circadian rhythm is our sleep/wake cycle.

          Clockwork Cells

          Circadian rhythms (CRs) seem to be a property of almost all life forms, including unicellular life and bacteria. At a molecular level there is a circadian clock which drives a near 24 hour internal oscillation that adjusts the internal physiological rhythm to the external 24 hour cycle. We know what makes those internal clocks tick. There are a number of key clock genes which produce clock proteins. These genes and proteins interact to produce a molecular feedback loop that generates a near 24-hour oscillation in clock proteins. These rhythmic proteins then signal to the cell the time of day and what to do when. The CR does not, as we had originally thought, arise from lots of different cells working as a network, but rather it is the property of an individual cell.

          In complex multicellular life-forms, there is often a central or “master” clock which coordinates all other clock cells. In mammals the master clock resides within the brain and is called the suprachiasmatic nuclei (SCN). It receives light information from the eyes to entrain the 50,000 neurones within the SCN, and these then send out multiple signals to coordinate the rest of the body. The individual clock cells of the SCN use more than 14 different genes and their protein products to generate a circadian rhythm.

          Key Properties of CR

          A circadian rhythm is a special type of biological rhythm. A biological rhythm is a broad term for any rhythmic process. Some rhythms are generated by clocks whilst others are driven by the environment. A biological clock generated rhythm will continue under constant conditions of light and temperature. In addition to 24-hour circadian rhythms there are clocks that tick with a period of a year or 360-days and are called circannual rhythms, or tidal clocks, found in organisms living on the seashore who have biological clocks with a period of approximately 12.8 hours.

          Engraving of De Mairan by Simon Charles Miger

          The first property that defines a circadian rhythm is that it continues under constant conditions of light or dark. The rhythm will oscillate, but depending on the species the period may be a bit longer or shorter than 24 hours. In humans the clock is a bit longer than 24 hours, whilst in mice it is a bit shorter. The second key property is that these rhythms are temperature compensated. This means that the 24-hour rhythm does not speed up or slow down very much, even when the external temperature might change greatly. That is an important property because if the clock wasn’t temperature compensated then the circadian clock would be incapable of telling time. The third key feature is that CRs can be locked onto the external 24-hour day. Mainly the signal is light, although there are other signals, such as temperature.

          Some organisms can set their clocks based upon the clock-driven behavior of other animals. For example, mouse pups begin to set their rhythms before and after they have been born using hormonal signals from their mother. In the uterus the signals arrive in the blood via the placenta and after birth in the milk. Later when the eye/SCN projections have formed they can use light. We are not really sure if this also happens in humans. Malarial parasites can detect the time of day from signals in our blood and this triggers them to move to the blood vessels very close to the skin at night where mosquitoes bite and so pick-up the parasites. The mosquito will then bite another person and infect another victim.

          Importance of Routine

          The key advantage of having a clock is that it allows an organism to anticipate predictable changes in the environment, and fine-tune physiology and behavior in advance of those changing conditions. For example, if you know that dawn will be in three hours’ time, you can start to increase your metabolic rate, increase core-body temperature, increase muscle strength, increase blood flow and prepare for activity. All of these prepare you to be active, when the morning comes, to get out there and fully exploit the new environment. If we simply waited for morning to arrive, we would waste lots of time adjusting to the new environment and not being fully able to exploit the “new” conditions. And in the same way, at the end of the day, when we start to go to sleep, body physiology begins to be reduced and turned down, preparing the brain and the rest of the body for sleep. During sleep the brain is very busy, establishing memories, processing information to come up with new solutions to complex problems, instructing the rest of the body to repair damaged tissues, rebuild metabolic pathways and organize energy reserves. Some part of the brain are more active during sleep than wake. So although we are not moving the brain is incredibly active performing essential activities needed for the next day of activity. The ability to predict and anticipate, rather than merely respond, allows an organism a huge selective advantage in the struggle for existence.

          A circadian clock can also be used by some animals and plants to detect the seasons. If an organism can measure the daily changes in the amount of dark and light, and if the duration of darkness is increasing or decreasing then it can determine the time of year very accurately. The increasing night length in the autumn in the norther hemisphere can be used to signal to some mammals to prepare for hibernation or in other animals such as deer and sheep it can trigger the urge to mate. Mating in the autumn means that young will develop over winter and arrive in the spring when there weather is usually good and there is lots of new plant growth to feed upon. Some mammals also change the thickness and colour of their fur to prepare for winter. For example, Arctic foxes produce thicker whiter fur to help them survive and for camouflage. Humans also show some seasonal biology. It is not very obvious in most of us, but changes in appetite and weight gain are often reported and some people show more depressive behaviours in the winter months. How these changes are driven remains unclear. It is also likely that in the past we were more seasonal than we are now. Partly because now we are protected from the external world by living inside, and the earth’s seasonal rhythms are no longer as sharply defined.

          How to Set the Clock

          A big question has been how the eye detects light for the entrainment of circadian rhythms. A recent discovery by our team has been that the eye contains a special set of light sensitive cells called “photosensitive retinal ganglion cells” or pRGCs. These pRGCs are quite different from the rods and cones that detect light or build an image of our world. They are formed from the “ganglion cells” whose projections leave the eye and enter the brain as the optic nerve. About 1-2% of the ganglion cells possess a blue light sensitive photopigment called “OPN4”.The pRGCs detect dawn and dusk and then set the molecular clockwork to the correct time of day.

          It is important to stress that if you have no eyes then all light entrainment is lost. Some people have claimed in the past that we have photoreceptors in the brain and even behind the knee. But such claims have never been supported by scientific study. Without eyes most of us will get up and go to bed about 30 min later each day as our internal clock is about 24.5, and not exactly 24, hours. There are tragic cases where individuals are born without eyes or have lost them as a result of an accident. Work is now underway to provide a “pharmacological replacement” for light. Basically a pill that fools the molecular clockwork that it has seen light and this will bring about entrainment.

          In addition to having no eyes there is another problem concerning light: we are not getting enough of it at the right time. Most of the time we remain inside and the light is not strong enough to set the clock. This is a particularly serious problem for the elderly, either at home and inside or in a nursing home. However, when the levels of light are increased inside stable circadian rhythms and sleep/wake patterns can be restored, and with restored sleep, brain function in these individuals improves. In humans, eating at the same time of day, and even morning exercise have also been shown to help maintain a good sleep pattern.

          Circadian Rhythms and Sleep

          In the developed and, increasingly, the developing world as well, help is badly needed to repair our sleeping patterns in what is now a 24/7 society. Our 24-hour rhythm of sleep is the most obvious diurnal rhythm exhibited by humans and many other animals, but there is more to sleep than the circadian system. Sleep is a highly complex state generated by multiple brain regions, neurotransmitter systems and modulatory hormones. This complexity makes sleep very vulnerable to disruption. Indeed, recent work has shown that sleep and circadian rhythm disruption (SCRD) is common in both neurodegenerative and neuropsychiatric illnesses where neurotransmitter pathways are disrupted. For example, SCRD is reported in more than 80% of patients with either depression or schizophrenia. But the inconvenience of feeling sleepy at inappropriate times is just the tip of the iceberg. SCRD is also associated with a broad range of interconnected pathologies, including poor vigilance and memory, reduced mental and physical reaction times, reduced motivation, depression, insomnia, metabolic abnormalities, obesity, immune impairment, and even a greater risk of cancer. All of which are frequently reported in both mental illness and neurodegenerative disease.

          The recent advances in our understanding of the brain mechanisms that generate and regulate circadian rhythms and sleep, and a growing appreciation of the broad health problems associated with SCRD, represents a truly remarkable opportunity to promote an understanding of sleep across society. Sleep is truly the best medicine and working at the wrong time can be disastrous – literally. Our alertness reaches it low point in the early hours of the morning, and it is no coincidence that accidents such as Chernobyl and the Exxon Valdez occurred on the night shift. Even allowing for fatigue and traffic volume, there is a disproportionally far higher incidence of car accidents at about 4.00 am than at other times of the day. And if we can’t help everybody with an increased awareness and prioritization of sleep then an understanding of the mechanisms and pathways that generate and regulate sleep is allowing the development of novel evidence-based treatments and drugs that will transform the health and quality of life of many individuals across a broad spectrum of society and illness. The potential impact of helping individuals resolve their sleep problems is enormous and within our grasp. What needs to change is that, at the moment, in most five year medical degrees the subject of sleep and circadian rhythms is only considered in one or two lectures.

          Howplantswork Weblog

          How Do We Know Plants Can Tell Time?

          The daily opening and closing of flowers and the rhythmic leaf movement of some plants suggests, even to the casual observer, that plants have an internal clock.

          To more careful observers, such as Carl Linnaeus and Charles Darwin, the evidence was clear that plants can tell time.

          For example, in 1751 Linnaeus published Philosophia Botanica in which he noted what time of day flowers of various species open and close.

          And also in this book, Linnaeus conceived the idea of a floral clock (“horologium florae“) garden by which one could estimate the time of day by observing which flowers were open and which had closed. (Click on photo of floral clock below for more information.)

          Darwin, assisted by his son Francis, studied the diurnal movement of leaves (sometimes called “sleep movements”, a.k.a., nyctinasty). In his book The Power of Movement in Plants Darwin argued that the plants had an internal clock that generated the observed rhythms, rather than them being solely imprinted by the diurnal cycle.

          Of course, we now know that these “sleep” movements in plants are manifestations of the circadian rhythm, which is evident in most organisms.

          What Sets the Clock?

          Think about it…what happens during the course of a typical 24-hr period on Earth? In simplest terms, it cycles between light/warm and dark/cool.

          So, what sets (entrains) the biological clock of plants are mainly light/dark transitions, augmented or reinforced by diurnal cycles in temperature. In other words, light (dawn/dusk) acts to reset the clock, but temperature also has an effect, albeit not very well defined.

          It turns out that, in most plants, the leaves play a central role in sensing the light that entrains the biological clock. But it’s not chlorophyll that is the light-sensing pigment, but two other non-photosynthetic pigments called phytochrome and cryptochrome. (Much more about these two photoreceptors another time.)

          How Does the Clock Work?

          Research on the cellular mechanisms of circadian (“about a day”) rhythms in plants has greatly advanced our understanding of how the clock works at the molecular level. (For an excellent review from an historical perspective see here.)

          Briefly, the clock works at the individual cell level and consists of three basic components as shown in the diagram below.

          It turns out that plants likely have three such mechanisms, all interlocked in a complex system, working inside leaf cells. As mentioned above, phytochrome and cryptochrome are the photoreceptors. These modify other proteins involved in a transcription/translation feedback loop that serves as the central oscillator.

          The collective output consists chiefly of proteins, and maybe even RNA, that serve to modify the plant’s metabolism and development. These output signals may even travel from the leaves through the phloem to other parts of the plant.

          Some Recent News About Plant Circadian Rhythms

          Leaves may have three interlocking clocks, but there may be only one root clock, and it’s apparently a slave of the leaf clocks.

          The circadian rhythm also apparently results in the rhythmic growth of plants.

          Researchers at the University of Texas at Austin have shown that modifying the internal clock may result in bigger plants.

          Much has been learned about clock genes in plants and how they relate to clock genes in animals.

          Bottom line: For hundreds of years people have recognized that plants have an internal clock, but only recently have plant molecular biologists discovered the complex inner workings of this timepiece.

          Download this article as a PDF

          Circadian rhythm 101

          If you’ve ever heard of the ‘circadian rhythm’, this was most likely in the context of sleep, in which it plays a very important part.

          For those of you who aren’t familiar with it, I’ll give a quick explanation: basically, our bodies have evolved to be adapted to the light/darkness cycle, a cycle that is about 24 hours long.

          Because of this, it’s called the circadian rhythm (circa dia=about a day). This adaptation causes our bodies to be active during the day, and rest during the night.

          Now, the circadian rhythm isn’t just for sleep, it does a ton of other things as well. It tells your body when to make certain hormones, neurotransmitters and other substances at any time of day, because it can’t do all these things at the same time.

          Basically, it’s your body’s daily to-do list.

          You can use this clock to plan out your daily activities (be sure to be near a bathroom at 08:30)

          Some examples of what circadian rhythm influences:

          • General health and risk of disease
          • Energy regulating hormones
          • Stress and youth hormones
          • Metabolism and appetite regulating hormones
          • Sleep/wake cycles
          • Arousal and alertness

          To know what your body is supposed to do at a certain point during the day, it needs to know what time it is. For this purpose, we have an internal, biological clock.

          But this clock gets out of sync really easy. It constantly adapts to the environment and needs the right signals to be able to tell the time. These signals are also called ‘zeitgebers’ (which is German for ‘time givers’).

          There are many zeitgebers, like movement, temperature and food intake, but the most important one, above all others, is light exposure. When light enters our eyes, it activates a part of our brain called the ‘suprachiasmatic nucleus’ (SCN), which is more or less our central clock.

          Light is basically the signal that tells your brain: ‘Hey, it’s daytime, it’s time to be active and get going and start hunting and gathering and do other stuff to survive.’

          Now, what’s the big problem?

          One issue we have in the modern world is that we sit inside all day, we hardly move anymore, we eat and snack from the break of dawn until late at night, and we have access to heating, so we’re always exposed to room temperature.

          Because of this, it’s very hard for our bodies to figure out what time it is, and what it’s supposed to be doing at any given time of the day. The most noticeable effect is on sleep, which definitely suffers a lot if your circadian clock is out of sync.

          And one night we go to sleep at 10 PM, the other night it’s 1 AM, and so on.

          All of this is very confusing for our body and continually disrupts our internal clocks.

          Not only will you sleep less and find it harder to doze off, the quality of your sleep will be diminished greatly too.

          This by itself is more than enough to lose focus and concentration and productivity, but there are secondary effects as well.

          For example, our bodies are primed to be much more wakeful and focused in the morning, before noon. When we wake up, we get a shot of cortisol which wakes us up and makes us alert and vigilant. In short, we get a huge mental boost.

          But as the day progresses, the hormones that are present in our brain and bloodstream change again, and we become calmer and less wakeful and less mentally focused.

          By the time it’s evening, you should be mellow and relaxed, in other words, completely prepared for a good night’s sleep.

          Unfortunately, because our circadian rhythms are out of sync, we don’t really experience this mental boost and clarity in the morning anymore. We have a hard time getting out of bed. A lot of people need caffeine just to be able to get going and start working.

          We stop noticing any big difference between morning and evening, between night and day. It all feels the same to us.

          Many people accept this as a normal way of life, while in reality, this is completely out of touch with how we should feel and live.

          So, even if you do get your eight hours of sleep every night, that doesn’t automatically mean everything is peachy. If your circadian rhythm is weak and your clocks aren’t working properly, your health, focus and productivity are going to suffer noticeably.

          Obviously, if we want to improve our focus and productivity, we have to make sure to get our circadian rhythm in working order.

          Okay, cool, so how do I do that?

          Well, the solution isn’t that hard. You just have to think like this: what would be the natural way of life, and then figure out ways to mimic that as well as you can.

          Imagine not living in a house or spending your day inside an office building, between four brick or concrete walls, with hardly any light exposure. Instead, imagine spending your day outside, exposed to massive amounts of sunlight.

          Even when it’s cloudy outside, the amount of light that our eyes are exposed to are vastly higher than the amount of light you’d get from a light bulb.

          Whereas inside you might get something of a 100 lux of light exposure (that’s the measurement unit of light), when outside, you can be exposed more than 100,000 lux.

          The differences are vast, and your brain will notice this too.

          The best way to improve your circadian rhythm: lots and lots (and lots) of sunlight in daytime

          So the most important thing you can do is to expose yourself to sunlight as soon as you wake up. Open up your window blinds, drive your bike to work instead of driving your car.

          If that’s too inconvenient, you can also buy a special light box that gives off high amounts of blue light (which is the kind of light that wakes you up) and make sure your eyes are exposed to that in the morning. At noon, you should try to go outside for another short walk so you can get some more light.

          The opposite goes for the evening. In the evening we’re not supposed to get any blue light exposure, which means it’s important to dim the lights and not spend the entire evening in front of the TV or your computer playing video games.

          Gaming at night: not the best thing to do if you want to feel wakeful and focused the next day

          One other thing you should do is make sure your bedroom is completely dark at night. Science has shown that even a tiny bit of light can throw off your circadian rhythm and impact the quality of your sleep.

          It’s also important to get more movement and don’t try to sit on your behind all day. Lots of activity is also an important cue for your body to tell time.

          It might be impossible to walk around all day if you work a desk job, but if you go for a daily walk and do a short workout every day, your circadian rhythm should still be noticeably strengthened.

          Other implications of circadian rhythm…

          As we’ve said, our brain is more wakeful and focused and more energetic in the morning (or at least it should be). That means that you should try to perform your most complex tasks, the ones that require the most brainpower and focus, in the morning. That’s the time of day when your brain is working at its best.

          If you have a lot of routine, less mentally draining tasks (scanning documents, checking e-mail), then try to move those to the afternoon, when your brainpower has diminished.

          In other words, try to do ‘deep work’ in the morning, and perform so called ‘shallow tasks’ later in the day. (here’s an explanation of what the terms ‘deep’ and ‘shallow’ work mean)

          Not only will this allow you to get more done, it will also ensure that you’ll produce work of a much higher quality.

          Now, there are always people who are going to say: ‘Oh, but this famous writer/musician/CEO always did his work in the afternoon, so in reality it doesn’t matter.’ or ‘I feel tired and unfocused in the morning, so this doesn’t apply to me’.

          But if that person had made a habit of working earlier in the morning, and had a strong circadian rhythm, he’d probably be able to produce much better work and do even more.

          And what if you think that you’re different and you’re ‘just not a morning person’? Well, it might be because you have terrible circadian habits.

          Try to get a lot of light exposure during the day and significantly increase your activity level for a while. See what happens.

          Lots of light + lots of activity = lots of well being and mental focus

          Not only will you experience massively improved sleep, you’re also going to feel much more energetic, mentally focused and have a ton more willpower than you did before. All of which work wonders for being productive and getting things done.

          Besides sleep and mental focus, there are other benefits to optimizing your schedule for your circadian rhythm. For example, people who lift weights in the afternoon are much stronger and have been shown to build much more muscle than those who workout before noon.

          Having a strong circadian rhythm really makes an enormous difference, and that’s why it’s important to plan your daily activities in function of what your body is supposed to be doing.

          Optimize your biology, and you’ll optimize your life

          There are a lot of things you can do to improve your health, your focus and your productivity. Eat healthy, exercise, get ‘enough’ sleep. Quit Netflix and drop your e-mail addiction. (Use FocusMe)

          But above all, one of the most important things you can and should do is try to optimize your circadian rhythm.

          So give it a try: move more, get more light and you’re sure to get more done.

          Watching the Body’s Clock

          Paying attention to your body’s natural cycle of wakefulness can be important. Studies show that our cognitive performance varies predictably according to where we’re at in our circadian rhythms, with regular peaks and dips in our attention spans, memory and executive function. It’s not just mental, either. One study found that Olympic swimmers tend to perform best around 5 p.m.

          Circadian rhythms have an important influence on our health, too. Researchers have found that heart attacks appear slightly more likely in the morning , when our blood pressure and heart rate is elevated. Our immune systems behave differently at night, too. Levels of proinflammatory compounds and white blood cells are more elevated at night , and dip during the day. It’s backed up by evidence that chronic inflammatory diseases and allergies worsen overnight, as our immune systems ramp up.

          The connection between medical conditions and time of day has given rise to the field of chronotherapeutics , based on growing evidence that some medications have more positive effects at some points in our circadian cycles. The field is still young, and more study is needed, but the concept could be a simple way to increase the effectiveness of some drugs.

          Just as sticking close to our circadian rhythms can help boost cognition or physical performance, straying from them can cause harm. It’s obvious that attempting difficult tasks late at night is more difficult for most of us, as our circadian rhythms turn our bodies down for sleep. But prolonged deviations from the normal cycle of sleeping at night and waking during the day can also lead to an increased risk of cardiovascular harm , among other things. Evidence shows that people with mental disorders see their conditions worsen when their circadian rhythms are destabilized. And the correlation goes the other way, too. Those with mental disorders are already more likely to have disrupted circadian rhythms .

          Though straying too far from the ticking of our internal clocks may be bad, there’s some evidence that we can alter our circadian rhythms, if just slightly. In a recent study, Harvard researchers say they were able to adapt subjects’ circadian rhythms to both a 24.65 hour day and a 23.5 hour day. A day on Mars happen to be exactly 24.65 hours, for example, and some researchers are worried that could spell trouble for future colonists whose bodies would gradually fall out of sync with the days and nights. But perhaps our circadian rhythms are more pliable than we think — just enough to keep time on another world.

          Watch the video: Mögen Pflanzen wirklich Musik? Kultur erklärt - Flick Flack. ARTE (August 2022).