Hard Wired
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Hardwired
In 2001 the surgeon general warned that obesity was the second largest cause of preventable death in the United States, quickly moving to overtake the leading cause, smoking (WWW1). Approximately one third of Americans are considered clinically obese (Clark & Grunstein). None of this is new information, movies like “Super Size Me” have shed light on the national epidemic and we are bombarded with messages about how to eat right by the media. Yet fast food still flourishes and obesity is on the rise. People for the most part understand that fast food is not healthy, yet they are still driven to consume it even when it is obviously killing them. What are the underpinning biological mechanisms that make fast food so attractive? This paper will analyze the neurological systems built to reward the body for survival adaptive behavior, specifically the endogenous opioid system and its neural physiology. Secondly, I aim to use a neuro-chemical lens to discover that good taste is only the beginning
of a complicated ballet of neurotransmitters and neurophysiology. First we will take a look at the underlying evolutionary and genetic factors that influence our everyday actions to see how they affect our eating behavior. Secondly this paper will examine the psychoactive components in fast food like casomorphins, Phenylethylalamine, and caffine. Third, we will explore the parallels between classic addiction as an analogy to understanding why we love the food that we do. Finally we will delve into the neural substrates that are activated by fast food. There must be a reason why fast food has found such a hold on American society and modern society at large. I argue that the reason is neurological, that humans (as most animals) are neurologically built to have an affinity for highly palatable high caloric foods like fast food. As Dr. Neal Barnard of the Physicians for Responsible Medicine says “It is not that you lack will power, These Foods stimulate the release of chemicals in the Brains pleasure center that keep you hooked.” (WWW4)
Evolution
When Homo sapiens first began walking the earth some 300,000 years ago, survival was very difficult (WWW2). Lacking modern technology or agriculture meant that food was at best an unreliable resource. The organism would thus benefit from seeking and eating food that was high in caloric value. One way of ensuring this behavior is for the brain to reward the organism when the desired behavior is acted upon, and highly caloric food was consumed (Kelly et al 2002). Our attraction to certain foods could also be an evolutionary adaptation for safe foods: “Sweet foods signal safe food with high caloric content, salt a critical mineral source, and fat a high energy source.” (Kelly et al 2002) It is also likely that we are adapted to liking sweet foods because our ancestors were arborous and had access to many fruits in their diets. These ideas are all speculative but they do explain our pull towards high caloric foods.
Genetics
Although it can be argued that food preference is largely influenced by culture, a closer look at what people eat reveals universal cross cultural preferences towards fats and carbohydrates. This trend is precipitated by genes that predispose us to fatty sugary foods. Monozygotic twin studies have shown that indeed there is a strong genetic component to carbohydrates and in particular sweets. The correlation for this “carbohydrate gene” was between .4 and .6, a strong correlation. Fat on the other hand had a lower correlation of between .2 and .5 (Clark & Grunterstein 2000). Thus it can be argued that we are at least influenced by our genes to seek food with high fat and carbohydrate content.
Psychoactive Food
It is difficult to imagine but when one is ordering a cheeseburger with fries and a coke they are really just ordering good feelings precipitated by psychoactive drugs found in the food. Researchers in the 1980s stumbled upon what they thought were morphine like molecules in cows milk. At first it was hypothesized that the morphine like chemical, named casein, were a biproduct from the cows diet since cows eat poppies and opium and its derivatives come from the poppy flower. It is possible that through metabolic break down that a form of morphine could end up in the cows milk. However, it turns out that casein is manufactured by the cow itself. As researchers delved further into this question, they discovered the casein exists in most mammalian milk. One might ask, “What is morphine doing in a mothers milk?” Casein breaks down into smaller molecules called casomorphines, which in a newborn, cause a calming effect. Its funny to think that a mother, in her attempt to stop a baby from crying is actually chemically silencing her baby into a state of calm. Researchers hypothesize that this association that the bond formed between mother and child is greatly influenced by this chemical interaction. Thus at a young age you are primed to crave foods with casein because it makes you feel safe, calm, and nurtured. Casein exists in several foods that are commonly eaten including some forms of sausage but more importantly cheese and most milk products. Cheese has the highest concentration of casein than any other food. One short chain of casomorphins (smaller molecules produced by metabolic breakdown of casein) has about one tenth the pain killing power of morphine, which gives the name comfort food a whole new meaning (WWW3). It is worthwhile to mention that many scientists do not believe that enough casein gets through the digestive track into the bloodstream to be psychoactive. French researchers have found though, that indeed some casein fragments do pass into the blood stream. One tenth the power of morphine is significant and perhaps people in fact do feel some effects similar to those of the pharmaceutical when they ingest milk products. This is an interesting prospect and explains in part why western societies are so fond of cheese and milk products. Regardless of the idea that casein may or may not be psychoactive, cheese (casein rich food) has been demonstrated by researchers to be a very desirable food. Researchers have also found that when they take people off of meat and dairy products that cheese remains as one of their main objects of desire (WWW3).
Another potentially psychoactive drug in cheese is PEA or phenylethylamine a drug with a similar structure to amphetamine. Researchers even think that PEA could be a form of endogenous amphetamine in some patients (Janssen et al, 1999). In another study using a mixture of PEA, Ephedrine, and caffeine, scientists trained