My coach says that I need to eat 1.2 - 1.5 grams of proteins per kilogram when I have a common cold and flu.
I normally eat one gram of proteins per kilogram, while double it when doing my exercise training.

He explained that the reason why you need to get more good proteins when you are sick is that the body is building antibodies by the adaptive immune system and later for innate immunity.

I think he can be right based only on my own experiences getting better from common cold with low protein diet - it just takes a lot of time, while under high protein diet, you get better faster.
I also think his explanation makes complete sense to me, since antibodies and antigens are proteins.

**Why do you need more proteins when you are sick?**