To my mind, we need to take examples from the life of the Companions[1] in these matters. When our loved ones get sick, we try to give them strong food to strengthen their weakened body. However, the Prophet (Peace and Blessing of Allah be upon him) used to advise people to drink telbine soup in such cases. Telbine was a type of low-fat, low-salt and low-spice milky soup made from smashed wheat or barley. It didn’t taste good, but it was very healing.
Our Prophet used to say that one should pay attention to his/her food during illness. When strong foods are eaten, our body struggles with digesting them, so the disease prevails. He would then say that the patients should be fed less, and then the disease would be defeated. One day, Ali ibn Abu Talib’s (may Allah be pleased with him) eyes became red and swollen (conjunctivitis), so he had to stay in bed. Our Master, the Prophet (Peace and Blessing of Allah be upon him) came to him and saw him eating dates and said: “If you want your disease to heal quickly, eat less.”
[1] The Companions of the Prophet Muhammad (Peace and Bless be upon him)