It 's coconut
Mike was not well. He was tried all the time, and his head often hurt. 'Go to the doctor', his wife said.
Mike did not like visiting the doctor, but after a week, he went. The doctor asked him a lot of questions and wrote Mike's answers down. 'What do you eat in the morning?' he asked him. 'Eggs, bread, butter, jam and coffee,' Mike answered. 'And what lunch do you have?' the doctor asked. 'Meat or fish and bread'. 'And what do you have in the evening?' the doctor asked. 'Eggs and bread.' Then the doctor said, 'Eat some fruit every day, and eat all the skin of the fruit. The skin is very good. What fruit do you like best?'. Mike was not happy. 'Coconuts,' he answered.