I’m assuming you mean if the sun dies out. If so, then most things on earth would die within a few days due to lack of photosynthesis and to freezing temperatures (which is what would cause humans to die).
Answer: The organic molecules required for building cellular material and tissues must come from food. Carbohydrates or sugars are the primary source of organic carbons in the animal body. During digestion, digestible carbohydrates are ultimately broken down into glucose and used to provide energy through metabolic pathways.
Hope this helps...... Stay safe and have a Merry Christmas!!!!!!!! :D