Thursday, August 11, 2005

Wired to Crave

People crave the very physical and emotional reward they feel when something they eat makes them feel good. This craving is set in motion by instinct, built upon an ancient strategy for survival that in our modern world occasionally goes horribly wrong. It turns out that our craving-addictive instinct may be what helped make us become the successful species we are today.

Addictions and cravings can come in all shapes and forms, but they all stem from a fancy piece of brain gear called the mesolimbic system. Scientists call this system the reward center of the brain. It works like an internal “High 5” in our brain - when we do something perceived as positive, it tells us “Great Job!” with the release of dopamine, a brain chemical that makes us feel good.

Dopamine is a group of just 22 atoms - eight carbon, eleven hydrogen, one nitrogen and two oxygen atoms - and it plays a significant role in our lives. All the pleasures we associate with certain behaviors seem to involve dopamine. Even something as straightforward as eating gives us a dopamine reward.

When we eat, or have sex, the brain processes a positive stimuli and releases dopamine very deep in our brain, in the nucleus accumbens. The more dopamine released, the better we feel. Interestingly we can get the same feeling by inserting an electrode into the nucleus accumbens and buzzing in a bit of electricity. Understandably, most of us prefer to just settle for a good meal instead.

When the brain rewards us in this way for certain behavior, our instinct is to repeat it, reinforcing in the brain to remember that it’s good for us. While ultimately the brain is not quite that simple, most scientists agree that on a high-level, things work in the brain in this way. The question is, where did this system come from?

Back when humans were far from being the dominant species, effective breeding was the only way to ensure survival and ultimately this meant passing on those genes that favored those who had a strong desire to have sex and find food. Those strong desires were driven by our ancestors’ reinforcement system – the ‘high-5 chemical’ dopamine - that encouraged them to undertake certain behaviors, like eating and reproducing.

Because the individuals with the drive to eat and reproduce were the most likely to pass on their genes, the end result was that their food and sex seeking genes were passed on to us. Even after a few thousand generations, we’re still carrying around pretty much the same genetic paraphernalia upstairs.

While we’ve evolved somewhat from our primitive ancestors into our modern selves, when it comes down to the nitty-gritty, we still need to eat, drink and reproduce in order for our species to remain successful. So the reward system has stuck around, making sure that when we aren’t enjoying our high-tech lives, we’re out looking for food and having sex. The problem is, because the dopamine system is so good at rewarding stimuli, and humans are so good at solving problems, we’ve worked out ways to short-circuit the system and get lots of dopamine in a hurry.

Scientists distinguish between natural rewards, those experiences we evolved to find positive because they contribute to our wellbeing; and artificial rewards like drugs and alcohol, which don’t necessarily add to our wellbeing as a species. Think of it this way, natural rewards are there to make sure healthy living feels good, whereas artificial rewards are there to just make us feel good no matter what.

The most obvious of the artificial rewards humans have stumbled upon are drugs and alcohol. These invade that ‘high-5’ area of the brain to such a degree that they provide a bigger reward than our brain is wired to manage. Over time the repeated over-stimulation of the dopamine system dulls the intensity of natural rewards from things like food and can over-ride our ability to manage the cravings for more and more reward. For some people, this continued pleasure seeking is very addictive because these substances fit exquisitely into our existing dopamine reward system.

Scientists are beginning to fully understand that drugs and alcohol are not the only addictive substances we seek in our never-ending quest for ‘high-5’s’ from the brain. While eating and drinking typically give us a tiny dopamine reward, some ingredients can give us a measurably larger shot of the stuff, especially sugar. In our modern world it is not uncommon to hear someone say they crave sugary foods.

Let’s not forget though, craving and addiction are two separate things. One can lead to the other, and you can have one without the other, but they’re not the same. Craving turns into addiction when the motivation for something changes from receiving a reward to trying to prevent feeling the nasty effects of withdrawal. It’s a switch from a perceived positive reinforcement – the pleasure from the substance – to a distinctly negative reinforcement - avoiding withdrawal when the substance is unavailable.

Today I’m not focused on the addiction side of things, but on the cravings. What sets up our cravings?

You may be surprised to learn that researchers have found that something as benign as talking about a substance can be enough to trigger cravings! Just mention “Krispy Kreme” and, for some people, that’s all it takes to make them crave a donut. Add to this our sense of smell…walk into a house where fresh cookies are baking and it’s a no-brainer you’ll want some. Then there are the visual cues we receive each day – everything from advertisements showing delicious looking treats to watching someone delight in finishing off their ice cream at the table next to yours in a restaurant. Oh, let’s not forget the mouth-feel of silky smooth chocolate mousse or the happiness you felt when you were a kid and your grandfather introduced you to your first taste of banana cream pie.

It comes down to memories and pure instinct.

Simple, positive memories of a pleasurable experience make us want to repeat it.

It felt good before, it will feel good again.

But, here’s the weird part – negative experiences can have the same type of effect.

Memory is complex and we can get confused about which experiences are positive and which are negative, especially if we’re unhappy, in a bad mood or tired. In our desire to alleviate the negative feeling, we crave something we remember gives us the ‘high-5’ from our brain. We do this rather than figure out what is causing the discomfort and relieving that – if we’re tired, rather than go sleep, we’ll eat a candy bar or grab a cup of coffee. People can believe they’re craving one substance when they’re really in need something else. So when you think you need a coffee, you might actually need some sleep or food.

Add to this the very real, very negative feelings created when you are trying to lose weight and eat things you know you shouldn’t. No matter how many times you repeat the process, you still crave more even though you know it isn’t going to make you feel better.

If you’re craving something, the worst thing you can do is try not to think about it – if you do that, all you’re going to do is think about not thinking about it. Now that might sound counter-intuitive, but the best way to beat a craving may be to spend a small amount of time with it and eventually move on to something else rather than ignoring it. Try to figure out what is driving the craving and take care of that rather than going for the ‘high-5’ from your brain.

Better yet, do something different - have a bowl of strawberries with cream instead of that candy bar, or go for a brisk walk - and start re-wiring your brain to give you a 'high-5' from a new, good for you, thing!

It’s important to remember that the mechanism that leaves us susceptible to cravings is also responsible for a lot of positives things too. All in all, we have a very well designed little system. But like anything, too much of a good thing can be bad, even dopamine. Cravings aren’t necessarily bad – they’re actually telling you that you do need something. Rather than just grabbing something sweet next time you have a craving, take some time to understand what is underlying your need for that ‘high-5’ from your brain and take care of that, or try a different thing for that reward, something healthy for you.

We know that it is not just food that provides the release of dopamine we need and desire – dopamine is also released when we’re happy, when we’re active and even when we sleep. If its sleep you need, take a nap; if you’re unhappy, go do something pleasurable, something you really enjoy; and if you’re just in a bad mood, call a friend and talk about it. Eating that sugary food you’re craving isn’t going to make you feel better – in fact, afterward, you may even feel worse!

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