Not drinking 30 minutes before a meal and 30 minutes after

Why can't we drink 30 minutes before a meal? I understand that we can't drink while we eat b/c it will push the food down the pouch. I also understand that we have to wait 30 minutes after to drink. But I am not sure why we can drink before a meal. Lisa

We greatly appreciate your interest in helping us build our Q&A database. To discourage vandals from posting garbage, however, we require people to register before posting.