Healthy breakfast. Two bowls of muesli laid out on a table with a jug of milk in the background. Muesli is made up of fruits and cereal grains, which have a high fibre content and can be processed to form flakes. Fibre is not digestible by humans, but it is an essential part of the diet as it helps keep a healthy muscle tone in the digestive tract. This helps food pass faster through the intestines, and so reduces contact with carcinogens that can lead to cancer.