Many years ago we took one of our dogs, a Lurcher, to the vet because he seemed to be producing a lot of a strange substance that we thought was bile. Also, at certain times of the day or night you could sometimes hear his stomach rumbling. The vet examined him thoroughly but could find nothing clinically wrong with him. He advised us to feed our dog twice a day instead of once as we were doing, so that there would always be something in his stomach for the bile, (which is being produced all the time) to work on. This sounded like such a simple yet obvious thing to do that we started to feed all our dogs in the morning when we got up and again about 5 PM. The rumbling and the bile stopped immediately and we have kept to this pattern ever since.
Of course, I don't mean that you start to give your dog twice as much food as before. Obviously, what you do is feed him / her half the amount in the morning and the rest in the evening, so for instance, if your dog eats 500 grammes per day, you give him 250 grammes in the morning and 250 grammes in the evening.
Bile is a very acidic substance and if there is nothing in the stomach for it to act upon it will start to attack the stomach lining instead. The result can be ulcers or even a perforated stomach wall. Both of these are painful and possibly life threatening conditions so please take a little extra time to feed twice a day instead of once.