The food combining myth has been circulating in various forms for a long time. I’m not sure where or when it originated. Food combining was advocated by William Hay in the 1920s with the Hay Diet. And Herbert Shelton promoted the ideas in the 1930s.
Food combining got a major shot in the arm with the publication of Fit for Life in the 1980s, a New York Times best seller. More recently, there’s the Body Ecology Diet program, which is popular and advocates for food combining. Even the likes of Dr. Mercola have advocated for the idea.
The premise of food combining is that different types of foods digest differently and that combining them “incorrectly” will wreak havoc on the digestive system, leading to all kinds of health problems from heartburn to cancer. There are a variety of food combining rules, but the most common are as follows:
• Never combine fruit with any non-fruits, but most fruit can be combined with other fruits
• Never combine melon with anything else
• Never combine dairy with anything else
• Never combine protein with starch
• Never combine sugar (as in fruit) with starch
There are plenty of other variations, including rules about how to combine acid fruits with non-acid fruits and so forth. But the preceding rules capture the essence of most food combining systems.
The reasons given for why food combining matters vary, but they are always fairly similar, and the most elegant explanation concerns two matters. First, it is claimed that different types of foods digest in different pH environments – protein in an acidic environment and carbohydrates in an alkaline environment.
Therefore, it is suggested that for this reason, protein and carbohydrates should be eaten separately. Secondly, it is claimed that different foods have different transit times when eaten alone and therefore should not be combined, because eating them together will cause one or the other to rot or ferment.
Let’s look at these arguments. First, it is true that protein and carbohydrates require different pH environments in order to digest. But the argument that they should therefore be eaten separately actually falls flat on its face. Here’s why.
Protein begins to be digested in the stomach, which is a highly acidic environment. Eating protein actually causes a further acidification of the stomach to anywhere between a pH of 1 and 3. The low pH is necessary for the protease enzyme pepsin to be active.
Pepsin mixes with the protein and breaks it apart into tiny, tiny pieces. It breaks the proteins into smaller proteins. Once that process is complete, the stomach empties into the small intestines. As the stomach contents (which are acidic) empty into the small intestines, the body secretes bicarbonate, which neutralizes and slightly alkalinizes the chyme from the stomach.
This is essential because the small intestines must be alkaline in order for the pancreatic enzymes to function. The pancreatic enzymes include enzymes for digesting fat, protein, and carbohydrates.
The enzymes work on the chyme to break it down into sugars, amino acids, and fatty acids that the body can absorb. And, interestingly, the more acidic the stomach contents, the more enzymes the pancreas will secrete, including enzymes to digest carbohydrates.
So it turns out that no matter what we eat, the pH of the stomach is low (acid) and the pH of the small intestines is slightly alkaline. This is true whether one eats fruit alone or meat alone or combines everything together.
And because eating protein can prompt greater enzyme secretion in the small intestines (indirectly by lowering the pH of the stomach), it turns out that eating protein and carbohydrates together probably increases the absorption of carbohydrates.
So this is a big fail for food combining, thus far. But what about the argument that combining foods may cause some to rot or ferment? Well, sorry, Dr. Mercola, but it’s not true. The extremely acidic environment of the stomach completely prevents fermentation. Anyone who has ever canned food knows that an acidic medium prevents spoilage.
Think about pickled cucumbers in vinegar, for example. The pH of the stomach is even lower than the pH required to prevent spoilage of canned food. So the potatoes you eat with steak aren’t going to rot in the stomach in the few hours they are in there.
Once the chyme enters the small intestines, the pancreatic enzymes begin to break everything down. Nothing is going to ferment for a few reasons. For one, the enzymes are breaking everything down and it is getting absorbed. For another thing, there’s nothing to ferment the sugars, since there should be no bacteria in the small intestines, and because anaerobic fermentation doesn’t happen in the intestines.
So once again, big fail for food combining. In conclusion, food combining simply doesn’t have any real merit. Humans have evolved over a very long time eating different foods together in the same meal, and our digestive systems are well adapted to it.
In fact, there is good evidence that eating different foods together at the same time is actually better than eating them apart from one another. Of course, some people may have problems with low stomach acid, for example, which can result in some digestive problems. In those cases, eating a low protein diet may seem to alleviate some of the symptoms.
But in the long run, it would be best to increase stomach acid production to healthy levels rather than avoiding protein. In fact, eating more protein may be one way to improve stomach acid production. And protein tastes better with carbohydrates. Dessert is good after dinner. And all of it together improves digestive function.