Dionne Warwick has famously said that when she gets a sore throat or finds her singing voice strained, she eats a whole pineapple for dinner. When she wakes up in the morning, her voice is usually crystal clear and feeling unstrained. The same goes for the rest of us--food can play a crucial role in the quality of our voices.
We all know that our vocal chords are muscles, so possibly the best approach is to think of ourselves as athletes who have to make sure our muscles are functioning at their very best. Just as athletes have to get a good balance between physical exercise and the proper nutrition, singers also need to properly exercise their voices, to rest their voices and also to eat properly.
However much we love our food, it is ultimately energy. Singing burns quite a lot of energy, so we should make sure we eat enough before we perform. But while we might not get a stitch from singing on a full stomach, it will be harder to do so. We use our diaphragms--situated just above that muscle--probably more than any other group of people and a stomach feeling like it's just about to burst won't help.
One important tip is that dairy products seem to increase the amount of mucus we produce, this means we should limit the amount you drink or eat before a concert. Possibly the best thing to consume if you are a singer, is water. So often we forget to drink enough water, but a proper amount of water will keep our vocal chords moist. Then remember that you shouldn’t consume carbonated drinks just before you’re about to sing--the last thing you want is loads of gas. Burping ain’t pretty. Finally, the basic point is that lots of fresh fruit and veg will help keep you healthy and less likely to succumb to infection.