The brain consumes about 80-100g of pure glucose sugar each day. More if hard problems needs to be solved.
The brain gets glucose from either a. sugars and carbohydrates from the diet or b. if there are no available carbohydrates, from the body turning amino acids into glucose and glucose like structures.
Option a. is a lot less stressfull for the body as a whole and studies suggest that it is better for abstract thinking. But too high blood glucose and fluctuation in blood sugar are also damaging
Option b. Keeps the body in constant stress mode (high adrenalin and tense), but the blood sugar is more stable.
The brain will however be stressed if there is too much glucose sugar around it, so the body controls the glucose levels in the blood constantly and try to add more glucose if the concentration is low and remove glucose if the concentration is high.
If you blood levels are low in glucose you feel somewhat tired and hungry for sweets to get you to eat some carbohydrates, though the body can and will release glucose from storage. If the blood levels are high in glucose the excess glucose will be stored as fat.
So do sugar have a good effect on the brain?
In a balanced diet with a moderate intake of sugars and other carbohydrates, yes. Then the body can easily control blood glucose and the brain will have a stable glucose level constantly. In a diet where high amounts of sugar is ingested at various times, no. The fluctuating glucose levels stress the body and then the brain have to take care of that.
Link Original: http://www.ibtimes.com/your-brain-sugar-2544852