DEAR DR. BLONZ: I want some perspective on a recipe known as “skinny soup,” which consists of cabbage, celery, onions, garlic, peppers, carrots, canned tomatoes and water. The rumor is that digesting this soup uses more calories than those found in the ingredients. It is also supposed to be anti-inflammatory. There are many different spins on this theme online, with an assortment of recipes out there. Any truth to this? -- C.N., Phoenix
DEAR C.N.: Small amounts of energy are indeed required for digestion, as well as for the conversion of proteins, carbohydrates and fats into different forms and structures. And our bodies’ metabolisms are not 100 percent energy-efficient; energy is lost, perceived by us as heat when our metabolism kicks into a higher gear. (Think about the heat you experience while exercising.) This also occurs during the digestive process after eating, a phenomenon referred to as the thermic effect of food, or TEF.
It is all part of the cost of bodily business. Once the body is in a “fed” state, the green light goes on to build, repair and put the excess away into storage; these are also functions that require energy, but are not 100 percent energy-efficient.
Foods with a low caloric density (few calories per unit weight), such as that soup, might indeed cause the body to burn more calories than they provide. The caloric difference, however, would not be that significant. However, if you get in the habit of substituting a low-calorie soup or salad -- or even a glass of water or a cup of tea -- for a more calorie-dense food, the net effects will certainly add up over time. That’s the real skinny. It’s not a magic soup; it’s just math.
As for the anti-inflammatory aspects, contributions to that element of the balance sheet would hold true for the healthful whole foods in the recipe -- as well as most other fruits, vegetables and whole grains, however they are consumed.
DEAR DR. BLONZ: This is another exceedingly hot summer, and as we all know, summer temperatures tend to soften fruits rather quickly. I have hesitated to refrigerate tomatoes for fear it would result in a loss of flavor. Is this a misconception, or should I go ahead and refrigerate? -- F.M., Hayward, California
DEAR F.M.: Refrigeration can slow the growth of many microorganisms, but it can also affect the quality of some foods. Tomatoes are best kept at room temperature, preferably in an airy location with moderate humidity. They should last about five or six days in these conditions. By placing the tomato in the refrigerator, you may delay it from going moldy, but flavor and texture are likely to be damaged in the process.
This is particularly an issue with flavorful homegrown varieties and those purchased at a farmers market. It may not be as much of an issue with store-bought tomatoes that have already been given a dose of refrigeration, as many markets store their produce in the cooler overnight.
Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to email@example.com. Due to the volume of mail, personal replies cannot be provided.