DEAR DR. BLONZ: I am seeking advice about eating various types of foods together, given that many are digested and absorbed differently. Proteins must be taken apart by stomach acids, for example, but carbohydrates and fats do not require this at all. When eating different foods at the same time, I am concerned that this is putting unnecessary stress on my body.
I have periodic digestive problems, and I was wondering if this might be involved. -- S.F., Phoenix
DEAR S.F.: Theories about "food combining" emerge every now and then: twists on the idea that the way foods are combined, or not, is the key to digestive health. Easy-to-digest foods such as fruit should not, the theory goes, be eaten with proteins or fats, which take longer to digest. The assumption is that having them simultaneously delays the fruit's digestion and causes its sugars to ferment and putrefy, which contributes to digestive problems. (This is a bit bogus, if only on the basis that stomach acids do not create a fermentation-friendly environment.) Other "forbidden" combinations include starchy foods, such as bread or potatoes, eaten with proteins, such as meat or fish.
There's no reason to believe this theory. The beauty of our digestive system is that it's designed -- from the mouth to the other end -- for a mixed diet. Different types of foods are handled in designated parts of the digestive system, which evolved to create an effective "disassembly line."
While it's likely that some people have found that certain food combinations don't work for them, this is more an indication of personal habit and preference than a defect of the human digestive system. There appears to be no physical reason not to include various foods at every meal. (Note: This is different from eating too fast, which can cause problems with even the most healthful diet. Read more on this at b.link/qupvvk.)
Eating can be one of life's great pleasures, so I encourage you to seek medical advice, or guidance from a registered dietitian, to discover what might be behind any recurring digestive problems.
DEAR DR. BLONZ: What is the difference between pasteurized and ultra-pasteurized dairy products? -- M.L., via email
DEAR M.L.: Pasteurization and ultra-pasteurization are heat treatments designed to reduce potentially harmful microorganisms. The two differ in the amount and duration of heat used.
Pasteurization heats a dairy product to 160 degrees F for 15 seconds, while ultra-pasteurization heats the product to 280 degrees F for up to 3 seconds. The higher heat used in ultra-pasteurization eliminates more bacteria and results in a shelf-stable product, but it can affect flavor.
Ultra-pasteurization is usually done on products such as half-and-half or whipping cream. But ultra-pasteurized milk can be found in stores in remote areas that don't sell a high volume of perishable products.
Once opened, both pasteurized and ultra-pasteurized dairy items require refrigeration.
Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.