The idea that food (at least some types) are addictive has been debated for quite a while and up to now mostly rejected by both nutrition and addiction researchers. Based on some recent research however, it is being discussed more seriously that food and drug addictions have much in common in how they affect parts of the brain associated with pleasure and self control.
What’s the evidence? Studies from Princeton and the U. of Florida found that when rats were allowed to binge on sugar and then the sugar was taken away, they showed opiate-like withdrawal symptoms including teeth chattering, forepaw tremors and the shakes.
There is a paradigm called the conditioned place preference. Rats are given a choice between two rooms and the rats become familiar with both of them. For example, inside one room, the rat is given injections of morphine or cocaine and in the other room, he/she is given a placebo of injected saline. Guess which room the rats hung out in most of the time – of course, the drug room – they had learned to prefer the effects of this room compared to the other (boring) room. This phenomenon continued even after the injections were discontinued.
In a study based on this paradigm at Connecticut College last year, rats were trained with Oreos in one room and in the other boring rice cakes. They spent just as much time in the Oreo room as they had spent in the cocaine or morphine room in previous studies. After that experiment they examined the nucleus accumbens (a part of the brain’s pleasure center). They measured the expression of a protein located there (c-Fos) that tells us when that brain center has been turned on or not in response to a behavior. They found a greater number of neurons that were activated in the nucleus accumbens in rats given the Oreos compared to animals conditioned to cocaine or morphine. This raised the question – do foods high in fats and/or sugar affect the brain in the same way as addictive drugs?
In a study published in Nature Neuroscience (2010), rats that spent 40 days eating bacon, sausage, cheesecakes and frosting became addicted by continuing to eat despite given electric shocks. Rats who were not addicted did not.
So much for the rats. A study published in the American Journal of Clinical Nutrition looked at how food intake is associated with dopamine-containing pleasure centers in the brain. Dr. David Ludwig from Boston Children’s Hospital and colleagues measured blood glucose levels and hunger and used MRI brain scans to look at brain activity during a four-hour period after a meal. This time span helps to influence eating behavior at the next meal.
Two identical milkshakes in calories, taste and sweetness were given to 12 overweight or obese men. One of the milkshakes contained a high-glycemic carbohydrate causing a rapid rise in blood glucose; the other contained a low-glycemic carbohydrate that takes longer to digest, thus a slower-acting blood glucose response.
When the volunteers consumed the high-glycemic shake, they experienced an initial surge in blood glucose levels that was followed by a sharp decline four hours later. The subjects also became extremely hungry. Brain scans showed activation of the nucleus accumbens which is also triggered by addictive drugs and even behaviors like gambling. These results may help to explain why some people overeat (however, all obese people do not exhibit this behavior) and provides a biological reason rather than just blame it on a lack of willpower.
Dr. Ludwig said: “Beyond reward and craving, this part of the brain is also linked with substance abuse and dependence, which raises the question as to whether certain foods might be addictive. These findings suggest that limiting high-glycemic foods such as white bread and potatoes could help obese people reduce cravings and control the urge to overeat”.
Dr. William Davis, writing in “Wheat Belly (a provocative book) has also proposed the theory that wheat is addictive. But remember, diet books often make bold statements to help them sell. He makes many claims that often are not supported by proper references, in my opinion.
From his book: “ It has been known for a century that opiates, when administered to lab animals and humans increase appetite. It was discovered about 30 years ago that the gliadin protein of wheat is, in effect, an opiate, as it yields digestive breakdown products that bind to the opiate receptors of the brain.”
For a critical review of this book: