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

When we fall sick, one or more organ-systems do not function normally. As a result, we lose appetite and do not have proper digestion and absorption of food. Sickness makes us weak. Therefore, we are advised to take bland and nourishing food during sickness. Such a food is easily digested and replenish our lost vitamins, minerals and other nutrients along with energy.