Biology 202
2004 Second Web Paper
On Serendip

Exhausted, you return home from work with a bag of McDonald's and flip on the television. Halfway through your juicy Big Mac, crispy fries and your 44oz. Coke, a public service announcement for the American Heart Association comes on at the tail end of the commercial break to tell you how you are currently sucking down enough saturated fat to harden the arteries of an elephant.

Whether or not you realize it, you are probably one of the millions of Americans bombarded by the anti-cholesterol revolution. Most people are aware of the well-publicized relation between high cholesterol and the risk it poses to our heart. However, a vast majority of individuals is unaware of cholesterol's surprising connection to behavior. This paper will investigate this rather interesting connection by first laying out the platform of the current cholesterol movement. Then, it will look at studies supporting cholesterol's impact on behavior. Next it will examine how these two viewpoints combine to provide a way of looking at "set-points" and the nervous system. Finally, it will consider why most people wouldn't anticipate this connection and the implications such a discovery might have about understanding ourselves.

It is well known that too much cholesterol in our blood is not a good thing – however is that the whole picture? For most people, the scare of coronary artery disease and atherosclerosis – where the insides of the arteries become hard and narrow due to (cholesterol) plaque buildup – is enough to make anyone shudder with any mention of cholesterol (1),(2). However, that does not mean that all cholesterol is bad. Lipoproteins carry cholesterol through the bloodstream in two types: LDL (low density lipoprotein), which cause buildup in the arteries, and HDL (high density lipoprotein), which carry cholesterol to the liver. Higher levels of LDL or "bad cholesterol" increase your chance of getting heart disease, whereas higher levels of HDL or "good cholesterol" do the opposite (2). There are healthy levels of both cholesterols in our bodies; however, there are no symptoms of high cholesterol so its only indicator is a blood test (1). In May 2001, the National Cholesterol Education Program (NCEP) altered the 1993 cholesterol guidelines (1),(2) by lowering the range of acceptable "normal" cholesterol levels. As a result, 13 million more Americans were advised to make dietary changes to lower cholesterol (3). The good thing, is that this measure is heightening people's awareness and generally increasing overall health. The bad side, however, is that this indirectly projects the mentality that "lower cholesterol is better". With the media and campaigns pushing an "a.s.a.p" lowering of cholesterol, are there consequences? Possibly ones we are not aware of?

We know that physiological deviation from what is considered "normal" can cause drastic results – high levels of bad cholesterol stymie the operation of our heart and cardiovascular system (1). But now lets challenge the completeness of this picture and ask, what about the other way around? How else does deviation from acceptable levels of cholesterol affect our body? Is there a consequence of having levels of cholesterol that are too low?

While the negative affects of cholesterol keep us maintaining low-fat diets for the benefit of our physical health, several studies raise suspicions that taking our obsession too far might be at a sacrifice to our mental health. Ignited by a Yale study proposing a cholesterol-serotonin hypothesis of aggression, Dutch researchers revealed consequences of low cholesterol by providing evidence that linked low cholesterol levels to increased depression in men (5). Subsequent studies support a connection between low/lowered cholesterol levels and adverse behavioral outcomes (aggressive behavior and depression) (4),(7). It is believed that cholesterol negatively affects the metabolism and activity of the brain neurotransmitter, serotonin, known to be involved in the regulation of mood. Other explanations target a certain type of fatty acid, omega-3, found in large quantities in the brain (6). It is speculated that low levels of omega-3 could possibly impact behavior through mechanisms still unknown. The focus of this information is not to undermine current wisdom and treatment of high levels of cholesterol on heart disease, but rather to focus on the possible connection between mental heath consequences and low cholesterol. The other significant consideration of such findings is how cholesterol might help us to better understand alterations in mood and behavior. More generally, these findings underline the notion that the role of the nervous system is more interconnected with, and impacted by, known physiological mechanisms than we were previously aware.

It is established that too much cholesterol is not good for you; however, it is incorrect to assume that the lower your cholesterol, the healthier you are. When we put the two pieces together, evidence advocating either side of the cholesterol argument suggests that the body is able to operate at maximum efficiency at an optimal level – a certain cholesterol set-point (8). Alternation of cholesterol levels below the "set-point," disturbs the consistency of serotonin metabolism and other unknown mechanisms that might act as a regulatory loop for behavior. An interruption of this process results in the previously noted behavioral outcomes. Cholesterol is something we cannot control; there are no symptoms of high or low cholesterol. We can't consciously manage the level of cholesterol in our body – inferring that such a regulation is not happening in our I-function. As a result, we have no direct control over our arteries clogging up with plaque or the metabolism rate of our serotonin and the "other part" of our nervous system must account for these mechanisms. In effect, we can extend this notion of the "other part" of our nervous system (I-functionless nervous system) to account for behavioral phenomena. We can use such reasoning to explain how cholesterol plays a role in behavioral outcomes, such as violence and depression, and occurs by way of set-point irregularity without the I-function.

Why did it not seem that these two sides could be put together to come to the above conclusion? Perhaps it has something to do with the fact that it is hard to actually bring to consciousness that which one is unaware of. For example, medical professionals might think they have a full explanation about the impact a certain molecule has on the body (in this case cholesterol), but not be aware of other existing pathways, loops or interactions. Cholesterol, studied from a physiological standpoint offered a very reasonable explanation for one particular set of medical outcomes. However, when approached from the standpoint of the nervous system, a new, previously unknown explanation is manifest offering further information about the linkage between cholesterol and behavior variation. In turn, we might question the true extent of our knowledge and ask if what we know really stops there.

Though this paper investigated the less known connection between cholesterol and behavior by using set-point variation and aspects of the nervous system, it raises concern over current knowledge of our physiological processes with emphasis on the completeness of what we think we know for sure. The nervous system offers an additional explanation about the connection between our bodies and behavior. If such connections were previously overlooked due to a lack of awareness about the existence of mechanisms between the nervous system and the molecular workings of our bodies, how might we become "aware" of mechanisms in our body that do not go through the I-function, but nonetheless exist and impact mental and physical outcomes? Another question arising from this discussion of cholesterol's impact on behavior through set-point alteration is if feedback loops that regulate set points are permanently alterable without the possibility of long-term negative consequences.

In this discussion, cholesterol is more than a culprit of heart attacks. As it turns out, we can use information from both sides of the cholesterol debate to shed unique light on how cholesterol can influence behavior by set-point alteration without our being conscience of what it is happening. Next time, don't be so quick to replace your #4 extra value meal with a soy burger, baked potato and a jug of OJ. Don't just do it...think for a second. Odds are, cholesterol goes to both the heart as well as the head.

References

1)Medicine Net, Site provides good general information about cholesterol in general, especially LDL and HDL

2)National Heart, Lung and Blood Institute, good information about anything having to do with the heart, heart conditions, cholesterol and heart disease

3) Dr. Mercola web page , a doctor's commentary about change in cholesterol guidelines, includes JAMA citations

4)Skali homepage, a good compilation of articles documenting the bad effects of having low cholesterol, good citations to articles

5)The Brain , This site showcases an article reported by Reuters News about Depression linked to low cholesterol summarizing a study by Dutch researchers in Psychosomatic Medicine.

6)New Century homepage, This site displays an article about the connection between mood and food with good references.

7)Science Daily, article about the price of low cholesterol among women, from the Center for the Advancement of Health

8)Dr. Mercola web page, a doctor's commentary about the link between low cholesterol, aggressive behavior and depression, includes Journal of Behavioral Medicine


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