Refined sugars have only relatively recently appeared in the diets of most people. Regulatory pathways that balance calorie intake and energy expenditure and reward pathways help the body regulate ingestion of these sweeteners, as well as other foods. The overconsumption of refined sugars, including sucrose and fructose, in beverages and prepared foods, undoubtedly contributes to the obesity epidemic that is escalating in the United States and throughout other industrialized countries around the world. Obesity is also linked to inactivity, economic considerations, and the ready availability of food, but is the real problem that these sweeteners act like a drug, leading to a cycle of food use and reward and addiction?

Many studies have uncovered commonalities between sugar intake and drugs of abuse, but a study in 2007 found that the reward experienced from sweetened food surpasses the reward experienced from cocaine. In this study, rats were allowed to choose either intensely sweetened water or intravenous cocaine. Amazingly, 94% of the rats chose the sweetened drink over cocaine. The rats made the same choice whether the water was sweetened with saccharin, an artificial no-calorie sweetener, or sucrose, a natural sugar. When the rats were sensitized to cocaine and offered increasing doses of the drug, mimicking drug addiction, they still chose the sweetened water.

Both sweeteners and drugs of abuse stimulate dopamine receptors in the brain, which are critical to reward and learning pathways. There is also a cross-tolerance and cross-dependence observed between sugars and drugs of abuse. For example, animals that consume large quantities of sucrose are tolerant to the effects of morphine. Also, naloxone, an opiate antagonist, precipitates signs of opiate withdrawal in animals that consume large quantities of sugar. Further, people addicted to morphine demonstrate a preference for foods containing large amounts of sugar. Last, adaptations in the brain of obese humans, namely in the regions involved in pleasure and emotions, are the same adaptations seen in humans addicted to cocaine and other drugs of abuse.

The authors of the current study on rats postulate that most mammals, including humans, have innate receptors for sweetness that are easily overstimulated by the sugar-rich diets available in modern societies. By constantly overstimulating these receptors, there is a greater than normal reward signal generated, leading to a loss of self-control and addictive behaviors.

Humans overconsume refined sugars because they taste good. When given a choice, most people will choose these palatable foods over non-palatable foods due to the rewarding aspects of ingestion. Many people overconsume these substances so much that they lose control over their eating habits and jeopardize a healthy body. Ultimately, the reward pathways overtake the regulatory pathways involved in feeding and energy homeostasis. But, are the rewards of food really related to the rewards experienced from drugs of abuse? The evidence in humans in unclear, but deserves more investigation. The addictive potential of food is intuitively appealing as many people struggle to gain control over their weight and eating habits and may offer new treatment options for obesity and its related metabolic consequences.

References

Magalie Lenoir, Fuschia Serre, Lauriane Cantin, Serge H. Ahmed (2007). Intense Sweetness Surpasses Cocaine Reward PLoS ONE, 2 (8) DOI: 10.1371/journal.pone.0000698

Levine AS, Kotz CM, Gosnell BA. Sugars: hedonic aspects, neuroregulation, and energy balance. Am J Clin Nutr. Oct 2003;78(4):834S-842S.

Levine AS, Kotz CM, Gosnell BA. Sugars and fats: the neurobiology of preference. J Nutr. Mar 2003;133(3):831S-834S.

P OLSZEWSKI, A LEVINE (2007). Central opioids and consumption of sweet tastants: When reward outweighs homeostasis Physiology & Behavior, 91 (5), 506-512 DOI: 10.1016/j.physbeh.2007.01.011