" A reminder to exercise and drink plenty of water:
Cellular chemicals greedily tear the molecular structure of glucose apart to extract its sugary energy. This energy extraction is so violent that atoms are literally ripped asunder in the process. As in any manufacturing process, such fierce activity generates a fair amount of toxic waste. In the case of food, this waste consists of a nasty pile of excess electrons shredded from the atoms in the glucose molecules. Left alone, these electrons slam into other molecules within the cell transforming them into one of the most toxic substances known to humankind. They are called free radicals. If not quickly corralled, they will wreck havoc on the innards...causing mutations in your very DNA.
The reason you don't die of electron overdose is that the atmosphere is full of breathable oxygen. The main function of oxygen is to act like an efficient electron absorbing sponge. At the same time the blood is delivering foodstuffs to your tissues, it is also carrying those oxygen sponges. Any excess electrons are absorbed by the sponges, and after a bit of molecular alchemy, are transformed into equally hazardous but now fully transportable CO2. The blood is carried back to your lungs where the CO2 leaves the blood and you breathe it out... keeping the food you eat from killing you.
This is why blood has to be everywhere inside you serving as both wait staff and hazmat team. Any tissue without blood is going to starve to death, your brain included. "
― John Medina , Brain Rules