Name: The Circadian Code
Rating: 4.5 (61 reviews)
Author: Satchin Panda

What’s in it for me? Sync your body to its natural rhythms to transform your health

Nearly every organism on Earth exhibits innate biological rhythms that align with the daily cycle of light and dark. These circadian rhythms are controlled by internal molecular clocks and regulate everything from sleep to metabolism. Through research on plants, animals, and humans, scientists have uncovered how circadian clocks work at the genetic level. They've also revealed how circadian disruption is linked to numerous diseases—from diabetes to cancer.

Recent findings, like the discovery of light-sensitive cells in the eye that synchronize our clocks to light, also explain how meal timing and fasting cycles drive circadian rhythms in organs like the liver.

This Blink will dive into how optimizing lifestyle factors like sleep, eating, and light exposure at the right times of day can strengthen your circadian clock. It gives a fascinating introduction to a new area of science – one you can use to enjoy better sleep, health, and well-being.

Seeing the light

Primitive humans naturally slept at night and were active during the daytime. The discovery of fire was a major turning point, as it provided light and protection at night. Still, for most of history, artificial light at night was rare and expensive.

It was only in the twentieth century, with widespread electric lighting, that humans really began extensively disrupting their circadian cycles. Shift work, evening entertainment, computers, etc. now stimulate our brains with light late into the night.

This allowed humans to work, eat, and play at all hours under bright indoor lights. But our bodies are still programmed to align with daylight. So constant artificial light – especially blue light at night from screens – disrupts our circadian clocks.

Light influences the body's clock through retinal cells called melanopsin. Blue light tricks them into thinking it's daytime, which suppresses melatonin and disrupts sleep. Chronic circadian disruption from modern lighting makes us prone to obesity, diabetes, depression, cancer, and more. Studies show that shift workers in particular, or those whose schedule changes from day to night work regularly, are particularly susceptible.

But understanding how light wavelengths affect melanopsin at different times of day can help optimize lighting to fight these effects. Reducing blue light exposure at night, for instance, and getting natural daylight in the morning, both help mimic natural cycles of light and dark to resynchronize circadian rhythms.

Further breakthroughs have uncovered that genes in the liver and other organs turn on and off cyclically, too. This daily genomic rhythm regulates metabolism. Disrupting it can lead to obesity, diabetes, and other chronic health issues widespread today.

So it isn’t just genetics that predispose people to illness or ill health, but how we follow, or disrupt, our bodies' cycles.

Humans are always on the clock

In addition to sleeping and waking, your circadian clock regulates the timing of thousands of genes, turning them on or off at specific times of day in every cell and tissue. When we disrupt clocks, even genes get out of sync.

For example, genes involved in digestion, metabolism, or cell repair activate on daily cycles. Disrupted clocks lead to these processes happening at the wrong times. Staying up late with light exposure can reset the master body clock in the brain, tricking it into thinking it's daytime. This puts it out of sync with other organ clocks.

The rhythms of the brain

In addition to all the other health benefits we’ve covered, circadian rhythms are also essential for maintaining brain health and preventing neurological diseases. Nearly every part of the brain has an intrinsic circadian clock that regulates its function. Disrupting these clocks contributes to many mental health issues.

The immunity clock

Circadian rhythms profoundly influence immune function and cancer susceptibility. Nearly all immune cells and processes follow innate 24-hour cycles for optimal defense. So disrupting clocks leads to an imbalance among immune components, which can cause the systemic inflammation underlying many chronic diseases. This means that things like shift work or pulling an all-nighter elevate infection risk and cancer odds.

The circadian clock controls cellular defense processes like autophagy – the recycling of cellular waste. Autophagy follows a daily rhythm, peaking during overnight fasting. Circadian clocks also regulate the production of antioxidants to neutralize oxidative stress from metabolism.

Restoring the rhythms of the gut

Nearly every aspect of eating and digestion follows daily cycles for optimal function, and misaligning these digestive clocks leads to many common GI issues. The production of enzymes, stomach acid, gut motility, nutrient absorption and more are all circadian processes.

In particular, late-night eating is especially disruptive, as it triggers excess stomach acid when repair processes are underway. This can cause acid reflux and create long-term damage.

Key ideas in The Circadian Code