Circadian (9): Surely a Little Glance Won’t Hurt?

“Is nighttime blue light really that bad? How is it possible that a quick look at a phone can do so much damage to the human clock? Aren’t people exaggerating this a bit much? I don’t want to miss the evening series on the tele—watching TV helps me sleep. Why don’t we talk about the bigger enemies of our health, like junk food?”

Those are valid questions. If you are asking them, it means you are either seeking scientific clarification or that you are in denial. Let’s assume it is the former, because in that case, I have the answers you are looking for. If you are in the latter group, only you can get yourself out of that rut.

The reason I am making this circadian series a priority is that I often see people who are already on top of their diet and exercise coming in with major health challenges. They have been everywhere and found no answers other than being prescribed pharmaceuticals or being told their results were "normal." When I look at their results—whether they are recent or decades old—I see a broken circadian rhythm staring back at me. Everyone has been looking for something physical, but time is a different dimension. You have to truly understand human physiology to ‘see’ human time.

To understand how blue light at the wrong time can be disastrous to our body clock, we need to understand the two key players in our pineal gland: AANAT and ASMT.

Let’s bring AANAT into the limelight first. It stands for Arylalkylamine N-Acetyltransferase, which is a mouthful. In a previous article, I said AANAT turns serotonin into melatonin; that isn't strictly true. You will realise that I sometimes simplify things to keep the blog digestible, but today you deserve the deeper story.

The pineal gland has a private, exclusive communication line for noradrenaline, which it receives only at night (according to the body clock). This is distinct from the noradrenaline in the brain involved in REM sleep or the adrenal stress hormone. This "private-line" noradrenaline tells the pineal gland to start producing AANAT. However, this line is severed by the presence of blue light at 30 lux or higher. When this happens, any AANAT already present in the pineal gland is instantly destroyed, as the enzyme needs noradrenaline not just for production, but for ongoing stability. You literally wipe out the entire AANAT population with a single blue light exposure, and it takes the system another hour to restart production.

But that is only half the problem.

AANAT doesn’t turn serotonin into melatonin directly. It converts serotonin into N-acetylserotonin and hands it over to ASMT, which finishes the process. Unlike AANAT, which is dependent on your current light environment, ASMT is always present in the pineal gland. ASMT’s activity depends on long-term light exposure patterns. Short winter days increase the duration of ASMT secretion, while longer summer days do the opposite. This is partly how our neurobiology and the Earth’s orbital experience are stitched together.

Due to ASMT’s slow and steady nature, this two-fold process causes a delay in peak melatonin production. A full hour of darkness is necessary for AANAT to be expressed, but initially, there is very little acetylserotonin for ASMT to work with. Because AANAT is a high-speed enzyme, if it is allowed to work undisturbed, we will have a significant supply of acetylserotonin about an hour after production begins.

Now we are two hours into the onset of darkness. ASMT will steadily convert this into melatonin, with production increasing over the next 2–4 hours as more "fuel" becomes available. This is how we normally reach peak melatonin concentration 4–6 hours after the last light exposure, depending on metabolism and thyroid health.

All of that hard work, however, is much like how Rome was built and destroyed. It takes seconds of light exposure to the eyes to damage AANAT and only minutes to annihilate it. After 10 minutes, you likely have a total collapse of AANAT in your pineal gland. If you then try to go back to sleep, the entire AANAT-ASMT-melatonin cycle must kickstart from scratch—a cycle that only reaches its peak after hours of operation.

Relate this back to sleep cycles, NREM 3, and the "power wash" of REM. They all shift. Quality NREM 3 and REM will have to wait. When your alarm goes off in the morning and you hit the snooze button, you are desperate for the time that a single short glance at a screen has stolen.