According to Susan E. Brown, PhD, cold foods and beverages slow down the rate of digestion because they must be “heated up" before proper digestion can take place. Cold beverages are removed from the stomach more quickly. Those at room temperature stay in the stomach longer. That is why marathon runners try to hyperhydrate and drink cold water before a race -- to prevent from becoming dehydrated. Yet, if cold liquids move through at a fast rate, they do not aid digestion.
My expertise comes also from Chinese Medicine and Bodywork Medical Massage.
In TCM cold drinks are not advised at all as cold is a pathogen in the core of a lot of medical conditions. In massage is a vasoconstrictor contributing to a slow down of metabolism. Stomach is a muscle and its action of breaking down food depends on its force. its force depends on the blood supply.
We must never forget that te stomach juices are made up of enzymes, so cold or really hot food can cause damage for these enzymes, how? hotter food can cause degenration of enzyme thus leading to digestive problems that can cause ulcers, while colder food can cause the malfunction of these enzymes leading to the delay in time of digestion leading to several GI deseases