Proper and complete assimilation of food is a result of the action of digestive enzymes, molecules that help break foods down into their smaller building blocks. When too many different types of foods are eaten at the same time, the body is unable to manufacture all of the multiple types of enzymes needed at once so some of our food is digested by the bacteria in our gut instead. This also happens when we combine foods that digest quickly with foods that take a longer time to digest.
Unfortunately, the bacteria in our intestines digest foods by fermentation, excreting toxic by-products such as ptomaines, leucomaines, alcohols, lactic acid, and carbon dioxide. Common symptoms of this pathological bacterial fermentation process include decreased nutrient assimilation, intestinal gas, abdominal pain, bloating, and heartburn. This process can be minimized or even prevented by what is referred to as food combining, intentionally eating foods in a certain order and in specific combinations.
Different foods require different digestive enzymes and some foods digest very quickly while others take a long time. In order to prevent pathological bacterial fermentation in your intestines, eat foods either alone or combined with only one or two other types of foods. In general, you should keep your meals as simple as possible, with a limited number of ingredients, and you should always eat copious amounts of green and non-starchy vegetables with your proteins, starches, and fats. Protein should be eaten at the beginning of the meal and in small amounts while fruits and fruits juices are best eaten at the end of meals or between meals. For those who are very ill or convalescent, well-cooked one-pot meals are most ideal.