DEAR DR. BLONZ: Is it not advised to drink water or a water-based beverage during the 30 minutes after eating? This was explained to me as having a negative effect on digestive enzymes and their ability to do their job. My confusion relates to the healthful practices of having soup or a large salad -- foods that are mostly water. -- P.H., San Jose, Calif.
DEAR P.H.: There is no fiction regarding the attributes of healthful soups and salads, but that water message has no place at the table.
Our key digestive enzymes don't come into play until the food has left the stomach and begins its travels through the small intestine. The dilution of digestive enzymes makes little sense, as enzymes attach themselves to specific parts of a specific food component. The issue here is the number of molecules of enzymes versus the number of molecules of their food component target. Water is not a target for enzymatic action so it has no major impact at this stage.
There can be exceptions, such as issues of transient bloating if excessive amounts of fluid are consumed while the food remains in the stomach. There also might be a problem for those with gastroesophageal reflux, as the extra volume in the stomach might encourage some sloshing up onto the esophagus while the stomach is doing its thing. Then there is the potential issue of aerophagia, the swallowing of air while one eats or drinks that subsequently leads to belching and is often confused with indigestion.
The point is that consuming water, or a water-based food, is fine; in fact, it can contribute to satiety and decrease the total amount of calories consumed. A study in the June 2005 issue of Obesity Research looked at overweight women on a calorie-controlled weight-loss program. It was reported that having a soup with a low energy density at the start of a meal led to more weight loss than consuming the same number of calories in the form of a high-energy-density snack food.
Energy density appears to be an issue with salads (and likely with soups as well), so we can't assume that very rich soups and salads work in the same way. A study in the October 2004 Journal of the American Dietetic Association compared no salad, a low-energy-density salad (9 calories per ounce) and a high-energy-density salad (about 38 calories per ounce). The difference in the energy came from the addition of cheese or a rich salad dressing. These salads were served in either a small portion (5.3 ounces) or a large portion (10.6 ounces). After the salad, the subjects ate as much of a pasta main course as they desired. Those having the low-energy-density salad as their first course consumed fewer calories during the entire meal. The small serving of salad reduced energy intakes by 7 percent, and a large serving correlated with a mealtime energy reduction of 12 percent. The results were different with the high-energy-density salad: Those having a small portion ended up having 8 percent more calories during the meal, and those with the large portion had 17 percent more calories.
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