Cortisol depresses the immune system. Cortisol also causes a dopamine spike, which is linked to addictive behaviour, and sugar binges have been shown to produce dopamine in the brains of rats. The brain adapts by reducing the amount of dopamine receptors and increasing opiod receptors. When the sugar supply was dropped, the rats exhibited anxiety as a withdrawal symptom. Alcohol is primarily refined sugar; studies have shown a high level of interaction between alcoholism and a preference for refined sugar consumption, such that often detox involves moving to a wholefoods diet.
While low blood sugar and hypoglycaemia causes feelings of being tired, restless, confused, and irritable, levels of serotonin and betaendoprhins in the brain are also affected by the food eaten. Low serotonin results in being depressed, reactive, impulsive, violent/suicidal, craving carbohydrates. Lower levels are also associated with PTSD. Beta-endorphin is an endogenous opioid creating affective stability and a feeling of well-being. Alcohol causes the brain to release beta-endorphins, and sugar and fat can also. In 1986 Dr Elliot Blass used sugar and naltrexone to demonstrate that sugar has a beta-endorphin based pain-killing effect, and affects isolation distress in mice. If you rarely consume refined sugars, or if have naturally low-levels of these neurotransmitters, the brain chemistry can become up-regulated and cause you to be more sensitive to this effect . Thus, binging on sugar after abstaining will cause an extreme high followed by an extreme low, often accompanied by lowered impulse control.