Why do actors become physically sick before a performance?
I have noticed an usual side effect relating to mental performance when fasting.
Periodically I do a 3 day fast for health reasons to give my immune system a chance to strengthen itself for personal healing.
The unusual result was that my mental performance was enhanced during these times.
During my leisure hours I participate in amateur trap shooting and noticed that my scores were much better when I was fasting.
I assume this would be the reason that actors become physically sick from nervousness before a performance as this is the bodies way of tuning the mind to get the maximum performance.
While I am on these fasts I hydrate constantly so this is also a factor in mental performance enhancement.
I do not recommend fasting unless you have your doctors approval after a through medical examination.