Why do we wake up at night at 2-3 o’clock not being able to fall asleep again until 5 or 6 o'clock?
As you probably guessed there is a perfectly logical explanation for this. The brain is highly active at night, it's busy transforming short-term memory into long-term memory and carrying out repair and regeneration processes, just as our whole body does. And the often seemingly annoying brain of ours needs a steady supply of energy to perform these tasks.
When we sleep at night our body goes into a fasting state. In order not to deprive the brain of the food it needs for energy, the body compensates by gradually raising cortisol, an adrenal hormone. Cortisol is made in the cortex of the adrenal gland. When it is released into the blood, it’s transported all around the body and in many places, it is highly welcomed, because almost every cell contains receptors for cortisol.
Cortisol can have lots of different effects depending on which sort of cells it is acting upon, controls the body’s blood sugar levels and regulates metabolism, controls salt and water balance, may act as an anti-inflammatory and can influence memory formation, among others.
Thus cortisol stimulates the body to release or create glucose to supply the brain with energy during the night when we are “unwillingly” fasting. Cortisol also can have an effect on blood pressure. People with hypoglycemia or low blood sugar levels tend to have difficulty making the right amount of cortisol at the right times, also the blood sugar levels can spike and then crash throughout the day. But this is valid actually for everyone, not just people with chronic hypoglycemia. If we go too long without eating we might experience irritability or spacey feelings, even other symptoms, all pointing at that the brain is not getting enough glucose. Our brain just loves sugar, can you blame it?! Anyway, in these cases what happens is, that the adrenal glands don’t produce enough cortisol to keep the brain fueled and the blood sugar drops too low. If this happens during the night, it is particularly unwanted because, in response, the body sounds the emergency alarm by releasing “fight-or-flight” hormones, the most "famous" is adrenaline. This would be awesome if it would not happen to be exactly 2 o’clock at night when you should be resting, not running a marathon. The stress hormones raise blood sugar back to a more satisfying level, at least what the brain is concerned… From the brain’s point of view, they did what they were intended to do: blood sugar got back to a safe level.
Unfortunately, adrenaline also makes us anxious or panic in the middle of the night. Hence the waking up at 2 a.m. and not being able to fall back asleep due to all those hidden sometimes little and insignificant details that happened during the day or 10 years ago and now at 2 am just start roaring like lion at night in your head. Everything receives new dimensions, we have new (most of the time) much worse perspective on everything and as the clock is ticking and we are tossing and turning like a chicken on grill thousandths of the time we might even lose all of our perspectives altogether.
We have all been there, we all have been grilled chicken. So, you might as well calm down. It is not the end of the word, especially cause there is so much you can do about it.
First and foremost we are what we eat: so don’t plan a huge sugary meal before bedtime. Might raise the question, why not, because sugar raises blood sugar levels, so at least it won’t be low… Well this is a point, the only problem is that what we need is not a huge spike in blood sugar level, as I mentioned before, because what goes very high in a short time – and from simple sugars it tends to do so- it will plummet just as easily and exactly that is our problem. Blood sugar level must be kept even. Before bedtime it is the best to consume food items that are famous for a low glycemic index, usually, all the stuff that is green, like spinach, cabbage, bruxelles sprouts, asparagus, green peas, paprika, etc and all the nonstarchy vegetables like cauliflower or any kind of seeds or nuts… There is a huge variety we can choose from. Of course they won’t take your breath away like a chocolate cake does, but as a simple advice, try to eat the chocklate cake during the day, and a couple of hours before bedtime only consume food items that are appropriate for your goals… of course in the case when your goal is to sleep the night through, whereas if you want to wake up at 2 and not be able to sleep again, stay with the cake at 22 o'clock and it is guaranteed that all the embarrassment you experienced in your life your briain will happily dig up and annoy you with exactly before the huge presentation you must make the next day.
Just deal with the fact that your brain doesn’t give much about your powerpoint presentation, job promotion or tests. Somehow, nobody knows how it is unable to comprehend that falling asleep at 5:30 only to wake up at 6 won’t do the job and no, that you cannot sleep till 11 doesn't comprehend either. Moreover doesn't care about your working hours either.
If you want to avoid getting up at 2 am, eat the spinach for dinner with some nice grilled fish, meat also will help to keep your blood sugar levels low, because it digests slowly and your brain will have energy all night, at least almost, so it won’t wake you up and won’t torture you with things that are highly irrelevant anyway. ( No company will build a statue for their workers just because they had one too many white nights because of the holy job issue and even if they did why on earth would you care about having a useless statue?! - but this thing our brain does not understand at 2 am at all... if it happens to wake up...)