Proponents of “food combining” argue that the body is unable to digest foods properly if they’re eaten in the wrong combinations, can lead to bloating, gas, heartburn, weight gain, malnutrition and even disease.
One of the tenets of food combining is that fruit should be eaten only on an empty stomach. Since fruit is digested more quickly than protein and starchy foods, you’ll realize its maximal nutritional value only if you eat it by itself. Eat it 30 to 60 minutes before a meal, or two to four hours after a meal. If you eat fruit in combination with other foods, though, it will get “trapped” in your stomach and start to “rot” before it can be digested and its nutrients absorbed. You’ll also feel digestive distress.
Another common food-combining rule: Avoid eating protein (e.g., meat, poultry, fish, eggs, tofu) and starchy foods (e.g., bread, pasta, grains, winter squash, potato) together in the same meal. The theory goes that since protein and carbohydrates require different enzymes to be broken down, enzymes that operate at different pH levels in the gut, eating them together will “cancel out” or neutralize their digestive enzymes and prevent proper digestion of either food.
The Real Story
The proposed rationale behind food combining goes against the physiology and biochemistry of human digestion. Our digestive tract is, in fact, very well equipped to effectively digest and absorb mixed meals.
Protein is partially digested in the acidic stomach and that carbohydrates are broken down into their building blocks in the alkaline environment of the small intestine. When food reaches the stomach – be it beef, fish, grains, fruits or vegetables (alone or in combination) – hydrochloric acid is released. The acidic environment of the stomach and its mechanical churning turns the food into a partially digested mass called chyme.
Hydrochloric acid also activates a protein-digesting enzyme called pepsin which degrades protein into smaller particles, which must then undergo further digestion in the small intestine.
When chyme enters the small intestine, the pancreas secretes different enzymes needed to digest protein (protease) into amino acids, carbohydrates (amylase) into glucose and fats (lipase) into fatty acids and glycerol. These small molecules are then absorbed into the bloodstream.
Pancreas releases all of these digestive enzymes regardless of what you eat, be it a steak with mashed potatoes and cauliflower or an apple with a cup of milk.
There’s no evidence that eating fruit with a meal, or eating brown rice with chicken, results in “gut rot.”, the harsh acidic conditions of the stomach keep it free of micro-organisms.
There are reasons, though, why some people don’t efficiently absorb nutrients from foods, including lack of stomach acid, prolonged antibiotic use, inflammatory bowel disease, pancreatic diseases and intestinal infections. But these factors are not related to improperly combined foods.
Reasons to combine foods
Eating protein and carbohydrates together, for instance, help keeps you feeling satisfied and energized longer after eating.
Combining fruit that’s high in vitamin C (e.g., strawberries, cantaloupe, etc.) with oatmeal will enhance your body’s ability to absorb iron from the cereal.
Adding calcium-rich milk or yogurt to a green smoothie can help bind oxalates from greens such as spinach, an important consideration for people with calcium oxalate kidney stones. Lentils, kidney beans, black beans and the like – are a combination of protein and carbohydrate.
Food-combining diet has been the subject of only one randomized controlled trial, which found no evidence that it improved weight loss or health above and beyond a balanced diet with controlled portions.