Books and programs on food combining have been on and off the best-seller lists for years. They should be in the fiction section. The authors claim that eating protein and carbohydrates, or fat and carbohydrates together causes problems because they require different enzymes for digestion, and either acid or alkaline conditions. They give you elaborate lists of foods that you can or cannot eat at the same meal. If any of this were true, the human race would be extinct. Few foods are "pure" protein, carbohydrate or fat. Your digestive system has evolved to deal with mixed foods, and the enzymes secreted by your pancreas can digest them all in any combination.
Your stomach is strongly acidic, no matter what food you eat. Stomach acid is much stronger than lemon juice, tomatoes or any other acid food. Nothing you eat escapes this acid "soup" while it is in your stomach, so it makes no difference whether you combine acid and alkaline foods.
These authors tell you that the undigested food will ferment and putrify, causing you to accumulate toxins in your intestines. This just doesn't happen. Your intestines do a very efficient job of breaking down carbohydrates, fats and proteins into their building blocks, which are then absorbed into your bloodstream. As long as you are not constantly constipated, your colon does an excellent job of removing the waste products of digestion. If you have a problem with constipation, the answer lies not which foods you combine, but in adding fiber and water to your diet.
They even claim that the undigested food makes you fat, which is impossible. To be stored as fat, a food must be broken down into its building blocks and pass from the intestines into the bloodstream. Any undigested food would be excreted, making you thinner, not fatter.
People who lose weight following these nonsensical rules do so simply because they are forced to limit their food choices and therefore consume fewer calories.
Do not confuse these ridiculous diets with serious "combination" recommendations that are made in two special situations:
Diabetics and others who are concerned about sharp rises in blood sugar are advised to eat fruits and root vegetables only in combination with other foods. Fruits and root vegetables contain lots of sugar or quickly digested starches which can cause blood sugar to rise after eating. However, a healthy diet does not eliminate these foods because they also contain lots of vitamins, minerals and other phytochemicals that your body uses to keep you healthy and prevent diseases. When you eat these foods WITH other foods, particularly proteins or fats, they are digested more slowly. Diabetics should include a variety of fruits and root vegetables in their diet, but eat them with meals, not alone.
Strict Vegetarians who eat no animal products are often advised to COMBINE beans and grains so they will get complete proteins. This is true, but you do not need to eat the foods together at the same meal. The proteins found in meat and dairy products contain all nine essential amino acids (the ones your body needs and cannot make), and so they are called complete proteins. Most plant sources of protein, such as beans and grains, contain only two to seven of the essential amino acids, so you must eat a variety of these foods to assure that you get them all. However, you can do this over the course of the day or week. Amino acids circulate constantly in your bloodstream and are used as needed. You do not need to eat the foods simultaneously to supply your body with the different amino acids you need.