"While it is true that there are demonstrable effects from drinking milk, coffee, or juice, they vary greatly from person to person. I think all advice regarding foods to eat or avoid should be offered with a big caveat: determine how things affect you, and then act accordingly. There was a period when I was singing children's operas at 9 am every morning. I actually drank a pint of milk before each performance because it seemed to help me keep my cords lubricated. (In fact, in one of those shows, I played a wolf with an upset stomach. We filled a Pepto-Bismol bottle with Nestle's Strawberry Quik, which I drank throughout the show!)
Juice, on the other hand, tends to gunk up the works for me. I just don't worry about eating chocolate - it seems to have very little effect on me. I still drink coffee almost every morning, and the only effect I notice is that I am more awake! (I picked up this habit when I was singing in the Spoleto Festival in Italy. We often had rehearsal at 8 am. I knew I could either get up at 6 am and warm up, or get up at 7:30 and have a cappucino on the way to rehearsal. The effects of each of these choices was similar for me, and the latter was much more appealing!)
When I was in college, I dated a woman whose mother was a professional oratorio singer. We spent a few weeks at her home, during which her mother had several performances. For three days before each performance, she would adhere to a strict regimen, taking naps at a specific time, and only eating certain foods. She was completely stressed out and very difficult to be around during those times, because everything had to be "just so".
I quickly decided that if I had to live life so strictly around every performance, I would rather do something else for a living! So, I made up my mind never to get so obsessed with singing that it made life unpleasant.
In fact, most of the professional singers I know are fairly easygoing in this regard. They are aware of specific things that have an obvious adverse effect on them, and they don't spend much time worrying about anything else.
And, in fact, this affords them the ability to avoid what probably has the worst adverse effect on the voice - Stress!
For advice on avoiding stress, I highly recommend visiting the website of my friend and mentor David Gordon at http://www.spiritsound.com/quotes.html. Be sure to read "How to stay stressed"!"
