Chocolate: A Dangerous Drug?

Scientist Nora Volkow’s research shows links between food and addiction. Food, just like drugs, is linked to dopamine.
  • Transcript


Question: Are there certain patterns of food consumption that lead to addiction?

Nora Volkow: Oh, yeah, and I do love chocolate. I just actually have found very few people that don't like chocolate. There are certain instances, of course, where you see people that are morbidly obese, where the notion of control of food is basically almost impossible. Where they don't want to be obese, I've never encountered anybody that wants to be obese, so I've been intrigued. That was the first question in my brain when I was saying, we are seeing these changes in the conditioning responses, in the ability to control in people that are addicted, but the behavior is similar to that, that you see in people that are morbidly obese. And so I've started to actually, systematically, that's how I started to use imaging to understand the brain. And again, dopamine is very important. Dopamine drives the motivation to it. In animals you can actually predict how much an animal is willing to press a lever in order to get the food on the basis of how much that stimuli is releasing dopamine. So the more it releases dopamine, the more the drive to get the food.

Now, why is it that some people are more sensitive to food versus something else or more sensitive to chocolate versus french fries? Well, again, food is more complicated than drugs. Because in drugs, where abuse start with is the rewarding responses. With food, what drives eating behavior is chemical signaling that are aiming at maintaining a balance of calories of energy requirements that responds to chemical signals that are just all throughout the body. That's one. And then the other one, pleasure and reward. Food can be very, very rewarding and reinforcing. And I would put the concept forward that most people that overeat, and we all overeat here or there, do it because food is pleasurable. And also, because food can decrease anxiety. So in a stressful situation, you can eat and that will decrease stress responses in your body. So food has the function of maintaining energy to activate reward and to also decrease stress. So it's not absurd that we have coined these term of comfort food, because it does decrease stress responses.

Now, when we are associated, normally and where glucose signals are saying you have enough energy, you can overcome the normal satiety response by putting food that you remember and you know tastes very, very good. So it's again, I don't think that it's satiety, that you have desert, and desert, one of the deserts is chocolate, right? Because you may be satiated, and there's no more dopamine that's going to be triggered by seeing a piece of chicken at that point. But may be triggered by a conditioned response that you have with that particular chocolate.

So just like we were discussing with drugs, where you've got condition, even if you are satiated, if you bring a stimuli that's salient enough, because you've had it in the past and it tastes very, very good, that will trigger the release of dopamine that will drive you to eat it.

Why do some of us fall into compulsive patterns and others do not? Many factors are going to be playing roles here. Again, aspects of vulnerability. But also, conditions. Look around yourself when you're in an airport and they cancel the flights. You'll immediately see people going in there and start to eat. So when you are stressed, you are much more likely to fall into one of these patterns of compulsively eating more food than you wanted to do. And this again has to do with some of the conditioned responses.

Our brains did not evolve at all for us to take drugs. What happened was that by just randomness of nature, certain chemicals, which we call drugs, are able to activate the same circuits that develop there in our brain to ensure that we will engage in a particular behavior. So therefore, it's not surprising that there's such a tremendous overlap. And the question that emerges is, why is then though, that if this is such an important process for survival, could it be that it goes wrong in such a way that people compulsively overeat and become obese at the expense of their own well being? Well, of course, this is of great interest because we are facing a massive obesity epidemic that is affecting the health of our society, and this is not just a problem in the United States, it's a problem everywhere. And this has to do with the social factors of easy access to food, food availability, diversity of food. Food that is extraordinarily appealing, that creates these conditioned responses.

So we got into the art of managed the most powerful food reinforcer, that for me, I would sort of say is chocolate, but for someone else it may be something else, but it's not just one chocolate. I can go there and there's all this diversity of chocolates. So I'm conditioned and if I take these chocolates and I get satiated by the taste, I can turn around to the left and there's all of these other variety that's it's now all intriguing. So we generated a system where many times, actually I ask myself, no wonder we have a problem of obesity in this country, I am surprised we don't have even a more serious one, because we are conditioned to the diversity of food. Food stimuli are everywhere. I walk, and now I'm in New York City, and oh, my God, I walk and they are all of these stores showing the most appealing food. And I'm conditioned to it, I mean, everybody's conditioned to it. I was commenting to you the story where you see that drug in a person that's addicted to drugs and you get that condition stimuli, we've done exactly the same study with food, people that are not obese, we just show them the food when they are food deprived, and you have exactly the same response. Dopamine system gets activated, you see the food, the dopamine system gets activated and that engages the motivational drive. So that's why when you go and see Godiva's chocolate on the glass, you want them, you want them! Of course you want them. And what you have to do is say to your brain, your frontal cortex, "No, I'm not going to eat it! No!" So you have to inhibit.

So we're constantly inhibiting. So that's what's happened to us when we get exposed to all of this food stimuli all over the place. We have to inhibit responses to want to eat it. It's just the way that our brain is hard wired. And that's modulated reaction.

Recorded on November 6, 2009