06/12/2012 12:45 EDT | Updated 08/12/2012 05:12 EDT

Blame the Caveman For Your Love of Junk Food

Did you ever wonder why so many people are attracted to junk food? Or why ice cream, french fries and soda pop so often win out over brown rice and broccoli?

It's not actually a conspiracy by fast-food companies to bewitch people into eating things that aren't good for them. Well, not completely. It's largely due to an evolutionary instinct that was useful when people wandered around in the woods searching for food, thousands of years ago.

In the distant past, we depended heavily on our senses to make a decision of what to eat and what not to

eat. In nature, foods that were sweet were almost always safe to eat and were good for us -- they made our

hunger go away. Foods that smelled odd, or tasted bitter or sour usually meant they were potentially toxic or spoiled, and less safe to eat. That was pretty useful information for a person who lived in a hunting and gathering era, and wanted to avoid starving or getting poisoned.

In the modern environment, where we buy food in supermarkets or restaurants, those same survival instincts are serving only to make us obese and chronically ill.

We have a routine choice of what to eat and how much to eat, and with depressing consistency we often

choose the wrong things -- the ones that carry lots of macronutrients, like carbohydrates, sodium and fats.

Because foods that are high in sugars, sodium and fats are readily palatable to us, we eat them too much!

The science of flavour -- how we taste and smell it, why we like or don't like it -- is still in its infancy. In a series of recent publications in Chemical Senses, we learned that the "congruency" of the different

components of flavour is a key to how we perceive the overall flavour of foods. Flavour components that seem to "go" together, like vanillin and sugar, are perceived as a unified sensation that seems to come from the mouth. And barely detectable vanillin becomes so much stronger when sugar is added to vanilla-flavoured drink or custard, making it even more palatable.

Actually, that's our brain playing a trick on us. Vanillin, the primary component of the vanilla bean, has

no sweet taste at all, it's only a smell. And the pleasant sensation is coming not from your mouth but from

the nose, through the passageway between the back of the mouth and the back of the nose.

Then, the final decision about what something tastes like is made in neither the mouth nor nose -- it's in your brain, where sensory signals are processed and "bind" as a unified, harmonious perception, like "vanilla custard." That data gets relayed back to your mouth where you believe the sensations are coming from.

There's just a lot we don't know about exactly how people perceive flavour, and how it plays a role in food choice and selection. When we learn more about these processes, it might be possible to more effectively

teach our palates to like what is good for us. In other words, to really enjoy eating broccoli just as much as eating an ice cream sundae.

The science of flavour is complicated. Some of the players include taste -- such as sweet, sour, salty, bitter,

and savory -- which is detected solely on the tongue; smell -- such as vanilla and basil -- which is exclusively

detected in the nose; and somesthesis, which includes things like touch (the texture of crème brûlée),

temperature (the warmth of soup), and irritation (the burn of hot peppers). All of these sensations provide

data to the brain, and it makes the final call.

If you really think you can "taste" everything in your mouth, take a sip of your favorite drink while pinching your nose, and see what it tastes like. Don't recognize it? Open your nose, and the familiar taste will reveal itself.

The perception of flavour is partly instinct but also a learned behavior. And because it can be learned, there are probably ways that we can teach it. Hardly anyone really likes the bitter taste of coffee the first time they drink it. Since the caffeine in coffee makes them feel energized, however, they learn to like its flavour.

We may never completely lose our desire for ice cream, and we don't have to. But science may help us find a way to deal a little better with our foods and our dietary choices.