Wednesday, April 17, 2013

The Nutrition Debate #100: Liquid Calories

What’s wrong with taking nourishment in liquid form? It’s certainly convenient, and if you make your own “smoothie” or some nutrient-dense concoction in a juicer or blender, you are assured of a “healthy” beverage of your own composition and making, right? Well, “yes” up to a point, but “no” for a host of other, very good reasons. Let me enumerate.

1)  The calories we drink go quickly “down the hatch,” no chewing required. Chewing is the first mechanical step in digestion. It takes energy (see The Nutrition Debate #52: “The Thermic Effect of Food” here) and time, not just the time spent chewing but also the time needed for enzymes in the mouth, stomach and small intestine to process chewed solid food into chyme and then further break it down to where it can be absorbed. If they have already been “liquefied,” these physiological functions are “side-stepped.” Liquid calories are absorbed more quickly and easily. In fact, in The Nutrition Debate #53, “On the Digestion and Absorption of Food” here, we explain 1) how some liquids are absorbed directly through the stomach wall and 2) how the priority of gastric emptying for those that are not is: liquids first and much more quickly than solids, then carbs, then protein, and then fat and fiber.

 2)  “The mechanisms controlling hunger and thirst are completely different,” wrote food writer and nutritionist Katherine Tallmadge in the Washington Post in this December 2004 piece. “Physiologically, your thirst is quenched once your blood and cell volume are increased by water. This sends signals to your brain that you are no longer thirsty. In contrast, hunger is regulated in your stomach and intestines. When you’re eating, nerves in the stomach wall detect that the stomach is stretching and send satiety signals to the brain. The intestines also release nerve regulators and hormones. At the same time, the level of the hunger hormone (called ghrelin), which is released by the stomach when it’s empty, is suppressed. All this helps you feel full.” Ghrelin doesn’t work as well with liquids as it does with solid foods. “Our bodies don’t detect the calories in these liquids foods the same way as when we eat solid foods,” Tallmadge said.

3)  Liquid calories add up in a way that can be surprising. The liquid calories in smoothies, juice drinks, sodas and even specialty coffees are stealthy. “A White Chocolate Mocha totals 410 calories (whole milk, no whip) or 510 calories with whip. In my world, 510 calories is an entire meal,” says Elaine Magee on WebMD. Tallmadge, in her Washington Post article, concurs: “When you consider that an appropriately sized meal is anywhere from 400 to 700 calories, and one 44 ounce Super Big Gulp is 800 calories, you understand the scope of the problem. A 16-ounce Starbucks blended coffee Frappuccino is 470 calories. A single mixed drink can set you back 300 calories. One glass of wine contains at least 100 calories. Double or triple these numbers at any given party, tack on the calories in your meals, and you can understand how weight gain is inevitable,” she adds. Tallmadge also notes, “Most caloric drinks consumed before or during a meal are not satiating and have little effect on how much you eat in one sitting or over the course of several meals.”

The good news, Tallmadge notes, is that “since liquid calories don’t contribute to feelings of satiety, cutting back on them doesn’t make people feel deprived; most find the change is an easy one to make.” So, what changes should be considered? The Harvard School of Public Health pondered this question and put together a Beverage Guidance Panel. Here are their recommendations from the March 2006 issue of the American Journal of Clinical Nutrition. Drink:


1) Water: Quelle surprise! But pure H2O does provide “everything the body needs – to restore fluids lost through metabolism, breathing, sweating, and the removal of waste. It’s the perfect beverage for quenching thirst and rehydrating your system” according to the group. Wish that we could end this list here! We used to, come to think of it.


2) Tea and Coffee: “Drunk plain, they are calorie-free beverages brimming with antioxidants, flavonoids, and other biologically active substances that may be food for health.” They especially recommended the strong green tea varieties served in Japan. However, the addition of cream, sugar, whipped cream and flavorings makes it “closer to a dessert.”


3) Low-fat and skim milk and soy beverages: Here’s where the Harvard School of Public Health/Beverage Guidance Panel and I part company. I avoid the carbs in milk and only take heavy cream (sometimes half & half). I am not afraid of saturated fat – in fact, I choose to eat it. I also avoid soy products altogether: soy bean oil, soy milk and soy sauce, etc.


4) Noncalorically Sweetened Beverages: This category includes the “so-called diet sodas and other diet drinks that are sweetened with calorie-free artificial sweeteners. They include stevia in this category too, and the liquid sugar alcohols.


5)  Caloric Beverages with Some Nutrients: This group includes “fruit juice, whole milk, sports drinks, vitamin-enhanced waters, and alcoholic beverages. The inclusion of all these beverages on this list in the number 5 (penultimate) position says it all for me. This list includes 100% fruit juice, which a blogger famously called a “liquid candy bar” a while ago.

6) Calorically Sweetened Beverages: These “least recommended” include drinks sweetened with either sugar or high-fructose corn syrup (HFCS). The two are basically the same. This group also includes noncarbonated soft drinks, fruit drinks, lemonade, and other “ades.” They’re just sugar calories with virtually no other nutrients and should be shunned.


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