Jane Says: Sugar Isn't Addictive—but You Can Eat It Like an Addict
With Valentine’s Day just around the corner, I should be opening a Maison du Chocolat box instead of Pandora’s box, but never mind. With the hand-in-hand prevalences of obesity and diabetes on the increase throughout the United States and the rest of the world, the scientific validity of food addiction—in particular, sugar addiction—is on the radar of every researcher who is trying to discover why millions of people pig out to the point where they develop life-threatening illnesses.
Our brains depends on a constant supply of glucose to function, so it’s no surprise that sugars in carbohydrate-rich foods have always been a part of the human diet. Scientists have long known that an innate preference for sweet-tasting foods is evident in infants and children around the globe; many think this characteristic arose because for millions of years, sweetness (i.e., ripeness) indicated edibility. Whereas fiber, for instance, was abundant in our ancestral environments, “it is extremely plausible...that we crave sugar and not fiber because we evolved in an environment where ripe fruit was both nutritious and in short supply,” wrote evolutionary biologist Marlene Zuk in Paleofantasy: What Evolution Really Tells Us About Sex, Diet, and How We Live. “Seeking it out meant gaining calories that in turn made it more likely the seeker would have enough nutrition to survive and reproduce, passing along his or her cravings. Nowadays, in a world full of processed sugar in everything from ketchup to Mars bars, this eagerness to consume sweets backfires....”
And how. Fatty liver, high blood pressure, gastroesophageal reflux, orthopedic problems, marked insulin resistance, dyslipidemia, and emotional problems related to weight are among the woes cited by David Ludwig, M.D., director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital, in The New England Journal of Medicine, and he was writing about kids.
Even though the term “food addiction” has been loosely used for decades to mean a strong preference or habit, can food really be as addictive as drugs or nicotine? After all, we don’t need drugs or nicotine to live (in fact, if they're given up, our lives markedly improve), but we need food, just as we need air to breathe. As far as sugar is concerned, self-diagnosed addicts feed their habit with cake, candy, cookies, doughnuts, ice cream, and so on. You would think they could satisfy their cravings instead with tangerines, bananas, grapes, watermelon, or mangoes, which are among the fruits highest in sugar and are healthier, to boot; in a July 2013 piece published by Ludwig in The Journal of the American Medical Association, he cited studies that showed increased fruit consumption is linked to lower body weight and a lower risk of obesity-associated diseases. But clearly it’s not that simple.
Leaving aside the food police’s current narrow focus on fructose (see the link above), for space reasons, let’s cut to the chase: the processed-food industry, with its sugar-salt-fat trifecta and principle of sensory-specific satiety. “The biggest hits—be they Coca-Cola or Doritos—owe their success to complex formulas that pique the taste buds enough to be alluring but don’t have a distinct, overriding single flavor that tells the brain to stop eating,” wrote New York Times investigative reporter Michael Moss in “The Extraordinary Science of Addictive Junk Food,” published in the Times Magazine about a year ago. The piece was based on Moss’ book Salt Sugar Fat: How the Food Giants Hooked Us, a must-read for anyone who wonders why food corporations don’t have our best interests at heart.
Last year, a research team led by Ludwig conducted a small but very interesting study that demonstrates how one particular dietary factor (the glycemic index, a measure of how a food affects blood sugar levels) that is distinct from sweetness or calories can trigger the pleasure center of the brain and encourage overeating. They conducted MRIs of 12 overweight men after they consumed two kinds of milk shake: The only difference was that one contained rapidly digesting (high-glycemic) carbohydrates, and the other, slowly digesting (low-glycemic) carbohydrates. Among the findings, published in The American Journal of Clinical Nutrition in June 2013, was that after participants consumed the high-glycemic index milk shake, they experienced an initial surge in blood sugar levels, followed by a sharp crash four hours later. That decrease in blood glucose was associated with excessive hunger and intense activation of the nucleus accumbens, a critical brain region involved in addictive behaviors.
According to the Yale Rudd Center for Food Policy & Obesity, which created and published the Yale Food Addiction Scale, “behavioral markers of addiction, such as continued use despite negative consequences and unsuccessful attempts to cut down, are evident in problematic eating patterns. Additionally, neurobiological research has identified similarities in the way the brain responds to drugs and highly palatable foods. Finally, animal models have identified marked similarities between sugar consumption and drug addiction. These findings have led to the hypothesis that certain foods may be capable of triggering an addictive process in susceptible individuals.”
Animal models have their limitations: One is that rodents metabolize fructose differently from humans, as Scientific American pointed out. But what makes some individuals more susceptible than others? I reached out to Nicole Avena, neuroscientist at the New York Obesity Nutrition Research Center at Columbia University and coauthor of Why Diets Fail. “So many scientists are trying to figure out what causes some people to occasionally use drugs (or indulge in a brownie)," she replied, "while for others it leads to a spiral of distress and addiction.... It is most likely that multiple factors contribute. Some people may have a genetic propensity toward addiction (meaning that they have perturbations in certain genes, such as the dopamine gene) that make them more likely to develop an addiction (be it to drugs or maybe even food). There is also the environment, which promotes addiction to food (via cues, advertising, and the social norms that make it acceptable to eat food pretty much everywhere and anywhere). It may be that some stressor causes addiction to ensue in people who are genetically prone, or who have been severely affected by the environment, or some combination of them both.”
More evidence is needed before food addiction can be formally recognized as a mental disorder, and that was a hot topic at last October’s European College of Neuropsychopharmacy (ECNP) Congress, in Barcelona, Spain. Speaking at the conference, Suzanne Dickson, professor of neuroendocrinology at the University of Gothenburg in Gothenburg, Sweden, noted that in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), a new class of eating disorder (binge eating disorder, or BED) and behavioral addiction (pathological gambling) is recognized. “Certain obese individuals appear to express addiction-like behavior, e.g., BED,” said Dickson. Although some 10 to 20 percent of obese individuals suffer from BED, it is not a major cause of obesity, and, in fact, often occurs in people of normal weight, she added. “In man, there is no solid evidence that any food, any ingredient, any combination of ingredients, or additive (with the exception of caffeine), causes us to become addicted to it.... Still, if we move away from food and concentrate on the individual, we can see that certain obese individuals express addiction-like behaviors."
The previous year, a London conference titled “Food Addiction—What Is the Evidence?,” organized by the British Nutrition Conference, was chaired by John Blundell, professor of psychobiology at the University of Leeds, who is concerned that the term “food addiction” is an oversimplified explanation for a very complex set of behaviors in millions of people. The reasons people reach for food, after all, can run the gamut from quelling low blood sugar or emotional trauma to coping with stress, frustration, loneliness, or boredom.
Bucking a culture in which overconsumption on all fronts is not just legitimized but celebrated is far from easy. Factor in a reliance on processed foods, a largely sedentary lifestyle, and the human brain, with its highly functioning reward system, and it’s no surprise our collective waistline is expanding. But prevalence rates show that the obesity epidemic cannot be fully attributed to addictive eating.
You wouldn’t know that, though, from the media, which fans the flames at every opportunity. In the matter of high-fructose corn syrup, for instance, read how public opinion trumps data in “Sweet and Sour: The Media Decided Fructose Was Bad for America, but Science Had Second Thoughts,” in Forbes. Another particularly egregious example is the widespread coverage of a Connecticut College study suggesting that Oreos are as addictive as cocaine in rats. All the news reports were based on one press release about a study that hasn’t been vetted by the peer-review process and published in a scholarly journal. I found that so frustrating I practically inhaled not one but three clementines. They tasted like candy, only better.