Jewish World Review August 8, 2006 / 14 Menachem-Av 5766
Dr. Ed Blonz
The skinny on diet soup; microwaving plastic and cancer; mangosteen
DEAR DR. BLONZ: Years ago, there was a soup called "skinny soup," which consisted of cabbage, celery, onions, canned tomatoes and water. Rumor had it that digesting the soup used more calories than those found in the ingredients. The soup comes around now and then but with a different name. Any truth to this? B.M., San Diego, Calif.
DEAR B.M.: Small amounts of energy are required for digestion, and for converting proteins, carbohydrates and fats into different forms and structures. We then need to consider that our body metabolism is not 100 percent energy efficient, so while things are happening, small amounts of energy are lost as heat. This thermic effect of food, or TEF, is part of the cost of doing business. When we eat, the green light goes on to build and repair, and put the excess away into storage. Foods with a low caloric density (few calories per unit weight), such as the soup you mention, might indeed cause the body to burn more calories than they provide. The caloric difference, however, is not significant. However, if you get into the habit of substituting a low-calorie soup, salad or even a glass of water or a cup of tea for more calorie-dense foods, the net effect can add up over time. That's the skinny. It's not a magic soup, it's just math.
DEAR DR. BLONZ: Friends are telling me about the seemingly endless health and curative benefits from the use of mangosteen in liquid form. I would appreciate any information you may have about this product. I am rather skeptical about it. J.R., San Diego, Calif.
DEAR J.R.: The mangosteen is a fruit native to Southeast Asia. Like any plant that has managed to flourish under the oxidizing rays of the tropical sun, mangosteen contains a compliment of antioxidant phytochemicals. As for there being "endless health and curative benefits," this sounds more like marketing talk than peer-reviewed science.
We have been down this road before with various types of fruits, vegetables and herbs. The more respectable commodities bank on the flavors and culinary qualities of their food for their sales. Funds get diverted into research, and there is a wait for positive results before any grand health claims are made. The bottom line is that there is no shortage of healthful foods, and they all deserve a place on your plate. There may indeed prove to be something special in mangosteen, but I could find no evidence from clinical studies. Regarding the fruit itself, it's supposed to have a unique, enjoyable flavor that has been variously described as sweet and slightly sour, with undertones of vanilla, strawberry and peach. I will keep an eye out for reliable scientific studies and will report back if there are any promising developments. As health claims should never outpace hard science, I would proceed carefully if your friends are trying to convince you to sell mangosteen products via multilevel marketing.
DEAR DR. BLONZ: I have been told not to heat food in the microwave in hard plastic containers, as the plastic secretes a cancer-causing chemical when hot. Is this true? M.S., via e-mail
DEAR M.S.: Assuming you are only using containers and wraps that are specifically designated as microwave-safe, the answer would be a qualified no. There may be substances in certain plastics, but we are talking about levels that are very low, well below any level of concern. There is a Food & Drug Administration article on plastic and the microwave online at tinyurl.com/ptxqt.
JWR contributor Ed Blonz, Ph.D., is a nutrition scientist and author of Power Nutrition and the "Your Personal Nutritionist" book series. Send questions to him by clicking here.
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