Really? I think that is true but that depends of how unhealthy and the amount of coffee someone drinks I guess..
Maybe I was to aggressive with my answer. 
There are other point of views on this as well. For example our Neurons need a constant supply of carbohydrates/glucose in our blood stream to function optimally, because they can not store glucose/energy as "regular cells" can.
Our body have other ways to regulate up the blood sugar levels/glucos in your bloodstream in order for your brain and nerve cells to not starve and die. But that process is a very complex process. You need to be like a Doctor or a researcher in order to understand it on a deep level. It's a very complex system.
When you don't have a steady supply of glucose (from food), just som surface level information.
Glucagon triggers your liver to convert stored glucose (glycogen) into a usable form and then release it into your bloodstream. This process is called glycogenolysis. Glucagon can also prevent your liver from taking in and storing glucose so that more glucose stays in your blood.
Code:
Source of QUOTE above: https://my.clevelandclinic.org/health/articles/22283-glucagon
That is why we can go an entire day withoutfood and our brain still works fine. Imagine if our ancestors didn't had their brain working when they had no access to food/fuel?
With my ADHD/Autism I really need to think about these things to optimize my brain performance when I need it. Drinking coffee gets me into hyperfocus mode and this is not always beneficial (when I can't control it, or are focusing on the wrong thing). Also I forget to eat and drink when I'm in hyperfocus mode.
So drinking juice when I need to focus on something for a long time can help me with the rebound effect from a session of hyperfocus mode (short explanation: Sitting more then 5 hours 100% focused on one thing without a break).
So I suppose drinking glucos (juice...) and drinking energy is not to bad, as long as we do it in moderation. But strangely enough being on 20:4 diet for 1 year did work for me, but it was not optimal. But I did feel more focused and did not experienced as much brain fog as when I was on a high carbohydrate diet. I ate mostly meat and vegetables (also some tubers like potatoes and carrots).
I don't know the underlying mechanisms/processes (can't explain them on a deep level) for this, but I'm sure someone knows this in this brotherhood?
But I think it has something to do with that our body and brain need to work all the time no matter, if there isn't any food around (for survival). If it didn't was the case we would die from starvation. No brain = no hunting/gathering food = death.
For example: Drinking to much water is not good for you either, if this results in you diluting your your body's fluids, and or depleting the important balance your body have by peeing everything out (the electrolyte balance...and so forth). I could go deeper in explaining this, but I do not have all the information easy accessable in the back of my head.
I think to much about penis enlargement so everything else gets pushed aside. 😂
Just wanted to expand the topic/discussion to a wider perspective.
Take care 🙂
*Edit by @squirt_inducer_man, due to clarification of the information.
