Some say that it's vital to eat foods in the right combinations - never combining, for instance, carbohydrates and protein at the same meal. They usually also recommend that fruits always be eaten raw and alone, because otherwise they will ferment and turn toxic in the stomach. There's no evidence to support such contentions, according to Dr. Sheldon Margen, Professor Emeritus of Public Health Nutrition. Nearly all foods are themselves combinations.
Bread combines protein, carbohydrates, a little fat and many other things.
A simple dish like macaroni and cheese, a peanut butter sandwich, or oatmeal with milk contains sugars, starches, protein and fat. Our digestive system handles food combinations very efficiently. The process begins in the mouth as we chew food and saliva acts upon it, beginning the breakdown of starches into sugars. Other enzymes come into play along the line, resulting in almost complete digestion and absorption of nutrients, no matter how they are combined. As for that supposedly fermenting fruit, anyone who has studied human physiology can tell you that fermentation does not occur in the stomach.