Why are we normally advised to take bland and nourishing food when we are sick

During sickness the body becomes weak, and the digestive system does not work properly. So easily digested food need to be taken during this period as well as food rich in nutrients are advised to take. The immunity of the body decreases during disease or infection. Fruits are mainly recommended by the doctors as it contains vitamins. Heavy food items like meat are always preferred least. It is also protein, but for a person who fall in sick will not be able to digest those food items. Thus bland and nourishing food is given for speedy recovery.