Question

why we are advised not to talk while eating food

Answer 1

We are advised not to talk while eating, because the food we eat might enter the wind pipe, other than of entering the food pipe. As when we talk, the wind pipe opens. When we talk while eating, the food may enter the wind pipe, other than entering the food pipe. Therefore, we are advised  not to talk while eating.
Hope this will help you.

Answer 2

When we breathe the epiglottis present at the junction of the wind pipe and oesophagus opens.When we eat food it closes but when we talk when we eat the epiglottis would remain open and the food may enter windpipe which may trigger violent coughing to clear the food material out of trachea.

Thats why it isnt advised to talk while eating.

Epiglottis is the valve which opens and closes for respiration which is present at the junction at the food and wind pipe.

Its main function is to protect wind pipe from foreign materials which may enter.

Hope it helps u.