Fat Chance: The bitter truth about sugar. Dr. Lustig Robert

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      Fig. 5.1. Supersize Me? A McDonald’s Meal and Its Nutritional Value. A Big Mac, large fries, and a large soda provide 1,360 calories (two thirds of a standard day’s allotment) and 1,380 milligrams sodium (almost an entire day’s allotment). While the fat content is 38 percent of calories (which is not bad), the sugar content is 95 grams, or 19 teaspoons, or 390 calories, which is more than double what the American Heart Association recommends for one day.

       Salt

      This sample meal contains 1,380 milligrams of sodium (salt). The 2005 Dietary Guidelines for Americans provided a “tolerable upper intake level” of 2,300 milligrams of sodium per day, which is why the %DV of the sample meal is 54 percent. Processed foods of many sorts contribute more than 3,400 milligrams of sodium per day to the average American diet. Salt is one method by which the food industry can preserve foods and increase their shelf life. So salt and calories almost always go together. (Think potato chips.) But is it addictive? Data to support addiction to salt are currently confined to animal models. Studies in rats show dopamine signaling in response to salt, and administration of opioids encourages bingeing on salt. However, in humans, salt intake has traditionally been conceived as a learned preference rather than an addiction. The preference for salty foods is likely learned early in life. Four- to six-month-old infants establish a salt preference based on the sodium content of breast milk, water used to mix formula, and the rest of their diet. But clearly people can modulate their salt intake. For example, patients who crave salt due to diseases of the adrenal gland can reduce their salt intake when given the appropriate medicine. Also, people’s taste for salt can be retrained; hypertensive adults can be retrained to a lower-salt diet within twelve weeks.⁹ So, based on the criteria for an addictive substance, salt doesn’t make the cut.

       Fat

      The high fat content of fast food is vital to its rewarding properties. This sample fast food meal contains 89 percent of the daily fat intake for an individual on a 2,000-calorie diet. In feeding studies, excess calories from fat are more efficiently stored than excess calories from carbohydrates (90–95 percent versus 75–85 percent). Therefore, fat intake has always traditionally been assumed to be the major determinant of weight gain. Animals will binge on pure fat when given intermittent access to it. They binge regardless of the type of fat ingested, which suggests that it is that fat content and not the type of fat present in fast food that encourages overeating (see chapter 10). However, rat models do not demonstrate other features of addiction to fat, such as tolerance or withdrawal. Keep in mind, however, that so-called “high-fat foods” are almost always also high in starch (e.g., pizza) or sugar (e.g., cookies). In fact, adding sugar significantly enhances preference for high-fat foods among normal-weight people.¹⁰ Thus, the combination of high fat along with high sugar is likely to be more addictive than high fat alone.

       Caffeine

      Soda is an integral part of the fast food meal. If you consumed a large soda with your McDonald’s value meal, the caffeine content would be approximately 58 milligrams. Soft drink manufacturers identify caffeine as a flavoring agent in their beverages, but only 8 percent of frequent soda drinkers can detect the difference in a blind taste test of caffeine-containing and caffeine-free cola.¹¹ Thus, the most likely function of the caffeine in soda is to increase the salience (the quality that makes it “stand out”) of an already highly rewarding (sugared) beverage. Dependence on caffeine is well established, meeting all the DSM-IV-TR criteria for both physiologic and psychological dependence. In fact, up to 30 percent of people who consume caffeine may meet the criteria for dependence. Headache (attributed to increased cerebral blood flow velocity), fatigue, and impaired task performance have all been shown during caffeine withdrawal. In addition, reinforcement of intermittent caffeine consumption leads to tolerance.

      While children get their caffeine from soft drinks and chocolate, adults get most of their caffeine from coffee and tea. An 8-ounce cup of brewed coffee contains 95–200 milligrams of caffeine, depending on how it is brewed. The late comedian and social commentator George Carlin famously referred to coffee as “Caucasian crack.” However, few customers these days order a regular brewed coffee at chain restaurants. A study of Starbucks customers showed that the majority of them order blended drinks.¹² The ever popular “grande” (extra large) Mocha Frappucchino (without whipped cream) has 260 calories and 53 grams of sugar. Thus, as a known substance of abuse, caffeine in coffee drinks and soda is part and parcel of the phenomenon of food addiction.

       Sugar

      Although anecdotal reports abound supporting human “sugar addiction,” we are still not completely sure whether this is full-fledged dependence or merely habituation. Adding a soda to a fast food meal increases the sugar content tenfold. While Coca-Cola estimates that currently 42 percent of soft drinks sold nationwide are diet drinks (e.g., Coke Zero), when purchased at McDonald’s, 71 percent are the sugar-sweetened variety. In fact, in 2009 only seven items on the McDonald’s menu did not include sugar—French fries, hash browns, sausage, Chicken McNuggets (without dipping sauce), Diet Coke, black coffee, and iced tea (without sugar). While soda intake is independently related to obesity,¹³ fast food eaters clearly drink more soda. It is likely that the widespread phenomenon of “soda addiction” is driven by the inclusion of caffeine, a known addictive substance.

      All criteria for sugar addiction have been demonstrated in rodent models.¹⁴ First, rats exposed to intermittent sugar access (following restriction) will binge. Second, these animals show signs of withdrawal (teeth chattering, tremors, shakes, and anxiety) when the sugar is withdrawn. Third, seeking and craving have been demonstrated where animals consume more sugar after a two-week imposed abstinence—just like Salvador and his soda. Elevated dopamine levels perpetuate the binge, and overconsumption increases with time, consistent with tolerance. Finally, cross-sensitization has been demonstrated in sugar-addicted rats who readily switch to alcohol or amphetamine use. So, based on the data, sugar is addictive, and soda is doubly so.

       Deconstructing Darwin

      There is some evidence that sugar may be addictive in humans. Experimental studies show that obese subjects will use sugar to treat psychological symptoms. Overweight women who were self-reported carbohydrate cravers reported greater relief from various mood СКАЧАТЬ