Yes, it’s all about the dopamine. It is well established that sugar causes dopamine release in the brain, similar to cocaine — and other rewarding behaviours (music, exercise!).
Carbs (sugars) send signals to your brain in (at least) two ways.
- They bind to the sweet receptors in your mouth, which send signals to your brain “do it again” (via dopamine release). All simple sugars and artificial sweeteners can “light up” your sweet receptors (by definition!). Since starches are only partially digested at this point, they don’t fit the sweet receptor and don’t trigger this signal (Read this article on the Potato Paradox).
- You also have taste receptors your GI tract. Here, starches and sugars act the same — “lighting up” the sweet receptors, as the starches will have been broken down into simple glucose units. The body’s response to these receptors is still under study but it relates to letting your body know about nutrient availability.
Read more about this fascinating topic here!
Based on these mechanisms, it makes sense that sugars would send the strongest signals, refined starches would be next, followed by whole grains. In terms of how much and how hard they hit your sugar-sensing systems, you can think of sugary drinks as sledgehammers, refined grains (e.g.cupcakes and simple white bread) as regular hammers, and whole grain starches as feathers ;)
It’s tempting to assume that sugar should be viewed as an addictive substance because it can lead to dopamine release. Yet, not everything that can cause dopamine release should be considered addictive (music, exercise, anyone?). There are many important differences between our dopamine (and behavioural) response to sugar versus drugs. Check out this great review article: Sugar addiction: the state of the science