As per scientific researches, its a phenomena that rise and fall in temperature of substances lead them to contract or dilate.
When we discuss human in vitro structures and their reaction to substances intaken, absorbed or adsorbed; the organs and viceras also react to the temperatures. When it comes to intake of liquid, especially cold water; it causes vasoconstriction (contraction of blood vessels) thats really hazardous for the human body.
With this, it slows down the process of digestion and in severe cases prolonged indigestion. This can cause fats not to dissolve and cause fat deposition in the abdomen. It can also cause constipation, difficulty in swallowing, congestion of respiratory system and hence all the issues related to congestion.
From mental health to physical health.