Tag Archives: internal clock

Photo by Moyan Brenn

Early morning not the best time to drink coffee

Photo by Moyan Brenn

Photo by Moyan Brenn

In the US alone there are an estimated 100 million daily coffee drinkers, each contributing to a booming $18 billion industry. Of these, 68% claim they have their first coffee within the first hour of waking up. As a coffee drinker, I find myself guilty of the same practice, but apparently this isn’t the best time to enjoy your coffee. Why? Because there’s a big chance you’re wasting it, even though you might feel like it’s giving you that big slamming kick to start off the day.

Every person has his up and downs during a day, whether we’re talking about productivity, mood or energy. These swings are caused by the circadian clock – an  internal 24-hour clock  that alters your physiology and behavior by modifying your biological rhythm. The circadian clock is governed by the hypothalamus, a part of the brain that contains a number of small nuclei with a variety of functions. Most importantly, the hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system.

[RELATED] How much coffee is too much? study says 3 cups is max

But how does the hypothalamus knows how to regulate time and thus send signals that affect our biology, like telling us when its to go to sleep for instance? Through interactions with the sun of course. Previously it was shown that there exist connections between the retina and hypothalamus (the retinohypothalamic tract), so direct sensory input, in our case light, influences the body. But you probably already know this, innately – you don’t need to know the science to feel the effects. Ok, but how does this relate to coffee? We’re getting there.

Your circadian clock controls your metabolism function of the time of day, including alertness. Alertness is related to cortisol (the stress hormone). Cortisol blood levels peak between 8 and 9 AM, then again between noon to 1 PM, and between 5:30 to 6:30 PM. So, basically you are already on full alert naturally in the very first hour of the morning and drinking coffee during this time makes consumption inefficient. Instead, the best time of the day to enjoy your coffee would probably between 9:30 AM and 11:30 AM, when your cortisol levels are dropping before the next spike.

Tip via NeuroscienceDC

How a rooster knows to crow at dawn

Way back before clocks were a thing, people had another natural way of waking up: the rooster’s crow. Now, a new study shows that they are so exact, that they don’t even need the light of a new day to know when it’s dawn – they just rely on their internal clocks.


Nagoya University in Japan

A rooster crows in a deforested Amazon cloud forest.

A rooster crows in a deforested Amazon cloud forest.

were studying the genetic underpinnings of innate vocalizations – which is just a fancy way of saying they were studying vocal behaviors that animals instinctively do without learning them – when they paid some attention to the ever-present (when you don’t want it) rooster song.

“To our surprise, nobody [has] demonstrated the involvement of the biological clock in this well-known phenomenon experimentally,” study co-author Takashi Yoshimura, who specializes in biological clocks at Nagoya University, said in an email.

During their experiments, they used PNP roosters—an inbred strain of chickens used often in laboratories because of their genetic similarities—through two different light regimens; on a sidenote, I didn’t even know that such a thing as PNP roosters exist.

The first group was exposed to 12 hours of light, and 12 hours of twilight for 14 days. During this entire interval, researchers note that roosters start to crow two hours before daylight. Meanwhile, the other group was placed in dim light for the entire 14 day period. Yoshimura and Shimmura noticed that the animals started running on a 23.8-hour day and would crow when they thought it was dawn, according to the study, published March 18 in Current Biology.

Even when the roosters were exposed to sound and light stimuli to test whether external cues would also elicit crows, they found that the animals rely more on their internal clocks than on external stimuli.

“Crowing is a warning signal advertising territorial claims. Our preliminary data suggest that the highest ranked rooster has priority in breaking the dawn, and lower [ranking] roosters are patient enough to wait and follow the highest ranked rooster each morning,” said Yoshimura.

Kristen Navara, a hormone specialist in poultry at the University of Georgia in Athens who wasn’t involved in the study said she isn’t sure why nobody looked at this previously.

“I think many times we don’t think to study what appears right in front of us,” Navara, who wasn’t involved in the research, said by email.

“[For instance] we have definitely noticed in our own roosters that they begin to crow before dawn and have wondered why that was, but just never thought to test whether it was a circadian rhythm driven by an internal clock rather than an external cue.”

Via National Geographic