Circadian (6): Good Morning!
Imagine that you have gone through all of the necessary stages of sleep we discussed at length in previous blogs. With your hormones fluctuating appropriately and a rise in cortisol, your body is finally ready to wake up. A region in the brain called the suprachiasmatic nucleus (SCN) acts as a timer, even while you sleep and have no idea what the time is. Sensing that melatonin is fading, the SCN triggers the brain to signal the adrenals to start cortisol production so we can experience wakefulness.
The magic continues as cortisol travels to the brain to stimulate our old friend, noradrenaline. Both are beautiful and necessary stress hormones required to stimulate wakefulness. If you are too "chilled out," you might not wake up at all. You will remember that noradrenaline’s concentration is low in the brain during sleep due to melatonin. Now that melatonin is gone and noradrenaline is back, it equates to wakefulness. You will open your eyes and allow the most powerful, yet taken-for-granted blessing to enter them: light.
As light enters our eyes, it finds its way to a part of the brainstem called the Raphe Nuclei and stimulates an enzyme to get to work. You will love this enzyme; it is called TPH2. It is the enzyme responsible for churning tryptophan into serotonin. Everyone knows serotonin thanks to SSRIs, but no one talks about how we can master it ourselves at home. Well, you are halfway there, as you have the first half of the knowledge regarding circadian rhythms covered from the previous blogs. Now we should tackle the next half—the daylight half of your body clock—to complete the circle.
To understand serotonin, we really need to look at its precursor, tryptophan. Tryptophan is an essential amino acid, meaning you must get it from your diet. What are amino acids, you ask? If proteins are like finished walls, amino acids are the clay that got turned into the individual bricks that make those walls. A lot of foods contain tryptophan, and animal-based sources provide it in plentiful amounts. Tryptophan is sucked up by the Raphe Nuclei as TPH2 is activated by light, subsequently turning it into our friend serotonin.
But not all light is created equal. When we talk about light, brightness matters. If you wake up and stay indoors to eat, exercise, read, or look at your phone, your eyes are never exposed to a brightness anywhere near 1,000 lux. A bright phone screen might give you 400 lux; a bright indoor room might give you 500 lux. The reason this 1,000-lux cutoff is important is because it is the minimum required to turn on the TPH2. You might think your sleep is good and therefore nothing is going to stand between you and your serotonin when you wake up—except there is. That will be the case until you go outside, or perhaps look out that big window you normally cover with blackout curtains.
You are in luck—or as one of my patients rightfully corrected me, blessed—because the outdoor world will give you at least 1,000 lux even when it is overcast. While 1000 lux is the minimum, if you want to perform, you want to think beyond the minimum. You don’t have to spend time directly in the sun for your eyes to register the brightness we are discussing. In fact, as I am writing this, I am sitting in the shade, but because I am outdoors, the brightness is everywhere. This is why we used to notice, before we got too busy to pay attention to our body’s needs, that sitting in a cubicle without windows is depressing. When I talk to colleagues in the UK about homes and workplaces, windows and the outdoors always dominate the conversation. In contrast, when I landed in Gold Coast in 2018, more than half of the rooms at the clinic where I worked had no access to natural light, and no one made a fuss about it.
From another angle, you can increase the amount of tryptophan available to your Raphe Nuclei so it can make more of your "happy hormone." If you have maximized your light environment and your TPH2 enzyme, you want to ensure your available tryptophan isn't so low that it holds back the entire production line. This is where things get exciting—and by that, I probably mean controversial. Let’s bring it on.
I don’t believe skipping breakfast regularly is ideal for human biology. Yes, intermittent fasting may help you lose weight. Yes, being too busy for breakfast may help you make more money. Yes, coffee can keep you going for longer without eating. But no, none of these are what your body actually seeks to achieve from within: an ultimately balanced state. When you have breakfast in the morning, I advise you to make sure it is laden with protein—the highest protein content of all your meals in the day. Chances are, tryptophan is going to flood the gates when you eat a protein-heavy meal, especially if it is animal-based. That isn’t to say plant-based foods are deficient; you just have to research your proteins, as not all of them contain high amounts of tryptophan.
Once in the body, tryptophan has to compete with other amino acids to make it to the brain. Its first challenge is that tryptophan molecules, unlike other amino acids, are chased by albumin in the bloodstream. Think of albumin like a storage tag; once you have this tag on you, you become a "storage" item instead of a "usage" item. The body does this because it likes tryptophan and wants us to have a constant supply of this amino acid at all times. About 90% of your tryptophan will be "storage" tryptophan. When you are not eating and your free tryptophan levels are low, the tag is removed so you can continue to make serotonin in the Raphe Nuclei. That’s why you still make serotonin while heating up your barbie outside to cook up your steak breakfast.
So, even if you have had a large protein meal, the amount of available tryptophan is not going to be on par with other amino acids like leucine, isoleucine, and valine (don’t worry too much about them now; they are for another day). The next challenge is that there is only one type of "door" through which all amino acids can pass to get to the brain: LAT1. Tryptophan isn't going to flood through if there are more of the other amino acids present and not enough free tryptophan molecules. This is where we come to the rescue.
When you include aerobic physical activity in the mix, you turn the situation around. The amino acid "big guns"—leucine, isoleucine, and valine—rush to the skeletal muscles due to the demands of your exercise. Suddenly, there is less competition for tryptophan to go through the LAT1 gates. At the same time, exercise spikes your adrenaline, a hormone that in turn burns fats, resulting in a spill of free fatty acids into your bloodstream. Albumin, upon seeing this, throws off the tryptophan and goes for the free fatty acids instead. Suddenly, you have a lot more free tryptophan available!
Remember, you still need that minimum of 1,000 lux. So don’t even think about going to a well-lit, tinted-windowed, indoor gym for your morning workout.