What is the natural Circadian Rhythm?

Circadian rhythm is a natural cycle that follows a daily sequence. It is approximately 24 hours in length and enables an organism to predict and adapt to changes in the environment. There are clear brain wave activity patterns, hormone production, cell regeneration, and other biological activities linked to this daily cycle.

Biological clocks produce circadian rhythms and regulate their timing. They’re composed of specific molecules (proteins) that interact in cells throughout the body. They are found in nearly every tissue and organ. Researchers have identified similar genes in people, fruit flies, mice, fungi, and several other organisms.

Therefore, the circadian rhythm is produced as a result of natural factors within the body, but the external environment can affect how it works. One of the most powerful synchronizers is light. Timing, intensity, duration, and wavelength of light all affect the human biological clock. The body’s master clock, or SCN, controls melatonin production, a hormone that makes you sleepy. It receives information about incoming light from the optic nerves, which relay information from the eyes to the brain. When there is less light—like at night—the SCN tells the brain to make more melatonin, so you get drowsy.

Light can speed up, slow down or reset sleep and wake times. For example, blue light suppresses melatonin production and is therefore used to treat disorders for sleep disturbances. LEDs appear to emit a bright white light, but in actual fact, LEDs contain high amounts of blue (in the 400-490 nm range). This blue light exposure is responsible for increased alertness and cognitive function, which can be useful for shift workers as they go against their natural body clocks schedule and need a bit of extra help to adjust. Studies have shown how blue light can help treat seasonal affective disorders such as SAD, increasing the amount of bright light in the darker winter months, replicating the amount of light exposure typical in British summertime.

However, too much blue light later in the day can have a negative effect. This is why sleep experts advise people to stay off their digital devices an hour before bed in order to ensure the blue light emitted by them does not have a negative impact on an individual’s sleep.

The circadian rhythm impacts sleep-wake cycles and hormone release, eating habits and digestion, body temperature, and other important bodily functions. Therefore, if you are someone who rarely gets outside to see natural light, your body clock can become out of sync quite easily. The knock-on effect of having an irregular rhythm has been linked to major physical and mental health conditions for a prolonged period. Some examples being: sleep disorders, obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder.

Research has shown that the largest drop in energy for most adults happens in the middle of the night (usually while we’re sleeping) and again just after lunchtime when we tend to feel a bit lethargic. However, if you have had a good sleep the day before, you will not feel the effects of these dips in energy as much; it is when the body is sleep deprived that the effects are stronger.

The best way to keep your circadian rhythm in check is to maintain regular sleep habits; this means going to bed and getting up at roughly the same time every day (even on weekends). If your sleeping patterns change either because you’ve flown halfway across the world and have jet lag, or you’ve had a heavy night out and didn’t get in until 5 am, your circadian rhythm will be disrupted. The result of this is feeling less alert and a bit under the weather; your body clock will adapt quite quickly and usually takes about a day to get back to normal.

Over the past decade, neuroscientific research has uncovered the existence of a previously unknown non-visual optic pathway modulated by the substance melanopsin (which has a unique sensitivity to distinct parts of the visible light spectrum). Unlike other projections of the visual system, these pathways seem to play a minimal role in the perception and processing of vision and image-formation; instead, they have been found to be fundamentally responsible for the entrainment and maintenance of circadian rhythms and other physiological functions.

There is still a lot to learn about how our bodies circadian rhythms function and what can disrupt and boost them, but science has uncovered many answers that benefit us today.

For more information about the impact of light on our circadian rhythm, please explore the rest of our website. We also have free downloadable research reports explaining the science behind circadian lighting in the care, workplace and education environments – click here to download yours.