You’ve got rhythm…and it’s based on light, not music! Since the 70s, scientists have been discovering how human bodies are designed to follow the rhythm of the sun, rising and setting every day. This is the body’s natural 24-hour clock, keeping you operating on a healthy wake-sleep cycle.
In the past six months there have been a flurry of headlines announcing research studies focusing on Circadian rhythm and how its disruption can negatively affect the human body. In Oct. 2025, the American Heart Association published “The Role of Circadian Health in Cardiometabolic Health and Disease Risk.” Then in February 2026, the publication Biogerontology published “Circadian rhythms in aging and longevity…” outlining how out-of-sync circadian rhythm can cause dysfunctional aging. And just this month Springer Nature Link published this article “Circadian rhythm and the gut microbiome…” reflecting on how circadian rhythm can affect our gut microbiome.
With heart disease, premature aging, even disruption of our gastrointestinal system, emerging research is making it clear: when our Circadian rhythm is off, our health will suffer. Yet this is a relatively new concept, and scientists are just beginning to discover the complexity of this signaling system.
Where is this “Master Clock?”
To clarify how Circadian rhythm affects humans, let’s start with what’s resting in your brain in your hypothalamus, just where your optic nerve splits. This area is technically called the suprachiasmatic nucleus or nuclei, commonly referred to as SCN or your Master Clock. It receives direct light input from the eyes to synchronize body functions with the 24-hour light-dark cycle. The most well-known master clock action is its daily evening signal to the body to sending out the hormone melatonin to encourage sleep and switch to night mode and then in the morning to stop the melatonin to wake the body for the daytime functioning. Most living creatures have circadian rhythms, including animals, plants, and microorganisms, although a few nocturnal species like bats and raccoons have their wake/sleep rhythm reversed.
And it’s not just the wake/sleep cycle
The master clock is not just limited to signaling for the hormone melatonin. It helps to coordinate the timing of the entire endocrine system, including other hormones which then act on the pituitary gland to direct the functions of the thyroid gland, adrenal glands, reproductive organs, and even the immune system, and the immune system.
It’s the recent research studies mentioned at the beginning of this article that are now clarifying how Circadian rhythm sends out signals throughout the day and night, which can influence your appetite, digestion, temperature, thyroid functioning, metabolism, even cholesterol. This is opening whole new fields of medicine. These promising new fields will be reviewed in next month’s health news report as well as how humans can cause disruptions in normal circadian rhythm – and how to help sync your peripheral and master clock towards normal health circadian rhythm.
Should you wish to learn more about this newsworthy, but admittedly complex, health topic, you can check out this 7-minute online video: “Following Your Body’s Circadian Rhythm: A Look at the Master Clock in the Suprachiasmatic Nucleus.”
