DEAR DR. BLONZ: Much of the advice I have received about managing my digestive issues has mentioned the need to avoid certain food combinations. This advice is based on the logic that “bad” combinations overwhelm the digestive system, preventing the foods’ nutrients from being properly absorbed and contributing to digestive upsets. Is this based in fact? -- O.C., New York City
DEAR O.C.: Foods are a complex combination of different types and sizes of nutrients and non-nutrient components. Our digestive system, by contrast, likes things simple. For our bodies to absorb foods’ components, foods must be taken apart piece by piece. Think of our digestive system as a “disassembly” line.
The digestive tract workers are enzymes: chemicals with specific abilities to pull apart the proteins, carbohydrates or fats in food. Enzymes are the epitome of specialization, in that each performs one action on one type of nutrient. For example, one enzyme splits big proteins into smaller pieces, while others break the small pieces into their amino acid parts. Similar-staged disassembly occurs with complex carbohydrates and fats.
We rely on over a dozen different enzymes to digest a typical meal. The beauty of the human digestive system is that it’s designed explicitly for that mixed diet. That means the advice you were given was off the mark. Since different food components get handled in different areas and by different enzymes, we don’t have to eat our foods one at a time.
Digestion begins even before the first bite: The cephalic phase starts when we see, smell or even think about food. We have all experienced our stomachs rumbling in anticipation of a meal. This is also connected to our tendency to eat meals at the same time most days, and becomes especially noticeable when a meal is delayed. In the cephalic phase, acid gets released in the stomach in preparation for the food about to arrive. In the mouth, chewing increases a food’s surface area and mixes it with our enzyme-containing saliva to facilitate the actions ahead.
The stomach is our high-acid, muscular churning compartment that denatures proteins. The acid environment activates certain enzymes involved in protein digestion, and it can also help destroy unwanted microorganisms hitchhiking on the food. The stomach is spared from self-digestion by a protective layer of mucus. Those with the misfortune of having gastroesophageal reflux disease, or GERD, have experienced the discomfort of the stomach acid splashing up into the esophagus, where that protection is not present. (More on GERD at b.link/7kae7.)
As the stomach completes its work, the partially digested mass of food, referred to as chyme, leaves through the pyloric sphincter. As the chyme departs, it is immediately doused with the body’s own antacid solution. Your meal is now in the small intestine, a veritable enzyme factory where the central part of digestion and absorption occurs.
Returning to your question, many of us may have found that certain foods or food combinations work best for us. Consider that we are creatures of habit, and our bodies do acclimate to the way we eat.
When making major changes in what we eat, it makes sense to do things slowly, but this advice is based more on our bodies’ habit-bred efficiency than a defect of human digestion. There appears to be no physiological reason to refrain from including a variety of foods at every meal.
Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.