Sunday, May 31, 2009

Food Addiction

Are you addicted to food? It is a question many have tried to answer. If you like sweet foods, chocolate, or pizza, does it follow that these foods have an unhealthy allure? There is a good chance that you crave food three times a day because you need food to survive. It’s called hunger. How does that differ to a desire to eat six Krispy Kreme donuts? (Here, I’ve made a wild assumption that Krispy Kreme donuts can be legally classified as a food).

Nutrient lack?
A favourite theory is that we crave foods that provide a nutrient that we lack. There is no science to back that view. Giving people a nutritionally complete milkshake for five days straight, and nothing more, still stimulated cravings for specific foods. Why wouldn’t it? Only milkshakes all day is boring. We are designed to enjoy a range of foods for pleasure, not just nutrients.

Chocolate is probably the most craved food in Western society. The common view is that chocolate, and cocoa specifically, has addictive compounds. Again there is no evidence for this. You will often read that we crave chocolate for its phenylethylamine (PEA). Two problems here. If PEA was addictive, then why don’t we crave cheese and sausages as they have greater amounts? Secondly, there’s very little PEA in chocolate, and the small amount present is rapidly broken down in the liver. Forget the PEA argument.

There is a lot of evidence that the consumption of pleasant foods, whether that is chocolate, lobster or a double cream brie, triggers the release of natural endorphins (opioid transmitters) in the brain. That means if the endorphins weren’t released at the time of eating, we wouldn’t enjoy the food as much. And that is exactly what happens. Taking a drug called Naltrexone blocks the release of endorphins and dampens the enjoyment of the food, yet doesn’t affect hunger. In fact, Naltrexone doesn’t cause weight loss, suggesting that a craving for food is not the main cause of overweight.

There is also evidence that the environment can elicit a need for certain foods. If life isn’t working out as it should, it makes sense to your body that you eat foods, or drinks, that are comforting and increase the brain opioid levels. Tough day? A gin and tonic with some chocolate will take away some of the pain.

What does it all mean?
Dr Marcia Pelchat from the Monell Chemical Sense Centre in Pennsylvania says it is difficult to find a direct similarity between food craving and drug addiction. A liking for food is healthy and had an evolutionary benefit in encouraging us to seek food we enjoyed. An addiction to drugs may affect similar pleasurable brain transmitters in an unhealthy way. A case of pleasure going haywire. She says that, however, some overweight people often do exhibit “addictive” behaviour regarding food and this is exacerbated when they go through cycles of restriction and abundance (as in going on and off diets) as that can produce an addictive pattern of eating.

Reference: Journal of Nutrition 2009; 139: 620-622

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