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Biology 202, Spring 2005 First Web Papers On Serendip

The Healthy Fat Craze; Fact or Fiction?

Kate Matney

A new health craze for the benefits of essential fatty acids (EFA) is gaining momentum in the United States and beyond. Supporters of EFA enriched diets believe that sufficient intake of these fats benefit health in seemingly endless ways. One suggested benefit of essential fatty acids is that it can treat arthritis. Recent studies propose that adequate intake of essential fatty acids not only reduces the inflammation of arthritic joints and relieves pain caused by joint-tissue degradation, but also inhibits cartilage-degrading enzymes that perpetuate the disease (5.) It is also believed that EFA supplementation improves cardiac health. In fact, the American Heart Association currently advises biweekly intake of fish because it supplies high quantities of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two essential fatty acids (4.)

These are just a couple of the areas where essential fatty acids may promote health. There are many other claims that other areas throughout the body benefit from a high dose of healthy fat. Perhaps the most striking of these claims is that essential fatty acids improve nervous system functioning. It is no surprise to us that drugs affect the chemical workings of our brain. Anti-depressants block re-uptake of serotonin and norepineephrine, dopamine receptor blockers are used to tame the spasms of epileptics, and even over-the-counter ibuprofen alleviates pain by intervening in biochemical pathways related to pain signal manufacturing. And yet, the concept that diet, like drugs, can alter brain functioning is a bit more difficult to trust. Is it possible that by consuming avocados (a source of essential fatty acids) we can improve our nervous system functioning and, by doing so make ourselves smarter? Is there anything to the Omega-3 health wave or is it just a fad of the holistic-medicinal world that with time will prove fictitious? In order to address these questions we must first understand what these health-facilitating fats are, where they work in the nervous system and how they are unique from any other fat.

There are three types of fatty acids (FA): Omega-3, Omega-6 and Omega-9 fatty acids. Omega-3 and Omega-6 are essential fatty acids (EFA) because the body cannot produce them independently. Essential fatty acids must come from the diet. Omega-9 fatty acid is not considered essential because the body can produce it without supplementation, although only in limited amounts. The dietary building blocks for fatty acids are three types of acids found in food. Omega-3 fatty acids are derived from Linolenic Acid, Omega-6 from Linoleic acid and Omega-9 fatty acids are derived from and Oleic Acid. Foods high in these acids include flaxseed oil, fish, and most nuts (2.)

On a molecular level the structural difference between bad and good fats is strikingly small. The difference lies in the presence of a single double bond in the carbon chain of the fatty acid. It is the absence of this double bond alone that makes bad fats saturated and its presence that makes good fats unsaturated. The number (three, six or nine) in the fatty acid name indicates the location of this critical double bond. It is fundamentally this double bond that yields great differences in the functioning of the fat and its derivatives in the body.

Although it does not directly involve the nervous system one crucial role of essential fatty acid in the endocrine system is worthy of note because of the parallel nature in which the endocrine system works with the nervous system to maintain body homeostasis. EFA is crucial in the production of a family of cell signalers involved with pain response, prostaglandin. Along with other endocrine signaling molecules (including prostacyclins, thromboxanes and leukotrienes,) essential fatty acid arachidonate is the precursor to this family of chemicals. Interestingly, the over-the-counter pain reliever aspirin works by actually inhibiting the cyclooxygenating step in the synthesis of prostaglandin from its fatty acid derivative (3.) It is the release of this fatty acid derived molecule that not only triggers pain development, but also fever and inflammation responses (7.) Hence, prostaglandin inhibition allows Advil to relieve pain and inflammation.

Beyond serving as a building block for cell signalers, essential fatty acids also play a direct structural role in the nervous system. Essential fatty acids make up 20% of neuronal membranes. Neuronal membranes play an integral role in the transmission and integration of information because it is between them that cell-to-cell communication and nervous system information processing occurs (8.) A recent study (April 2004) conducted by the Institute on Alcohol and Alcoholism in Rockville, Maryland confirmed the importance of essential fatty acids' presence in neuronal membranes (1.) Although the study looks at the consequence of reduced essential fatty acids in rat retinal cells, structural consistency throughout the nervous system makes the ramifications of the findings far reaching. Thus, their study uncovers much of the mechanisms behind the magic of healthy fats not just for vision, but also for information processing throughout the nervous system.

The experiment consisted of two groups of rats. One group was fed a diet deprived of the essential Omega-3 fatty acid, while the other group was given an Omega-3 adequate diet. The adequate diet differed only by its supplementation with flaxseed oil and fatty acid docosahexaenoic acid (DHA.) After ample time on the diets the rats' retinal rod outer segments (ROS), sensory neurons of the eye, were tested for the presence of DHA. They found that rats fed the deficient diet had about 80% less DHA in their retinal membranes. In the deprived rats the saturated poly-carbon chain, docosapentaenoic acid, largely replaced DHA. Bovine proteins were used to replace the rats' original ROS membrane proteins so as to eliminate the potential for differential protein functioning. This allowed the study to isolate the effects of membranous fats (essential and non-essential) on vision.

The speed and efficiency of the complex biochemical pathways of sight were then tested and compared in the two groups of rats. Because these pathways involve G protein-coupled receptors (GPCR), which are ubiquitous in biochemical pathways of cognitive function, the results support the potential for similar effects throughout the nervous system. The results showed that in deficiently dieted rats there was not only a reduced speed in the biochemical pathways of vision, but also weakened signaling strength in the GPCR pathway. Probable cause for the relative inefficiency of deprived rats is reduced flexibility of the cell membranes. Docosapentaenoic acid's saturated character results in less free volume than the unsaturated DHA's packing order. Since the GPCR pathway for ROS activation involves the formation of a membrane complex, less flexibility (caused by a lack of free volume) probably results in greater energy barriers for complex formation.

This study is not the first to correlate EFA deficiency with decreased neuronal functions. In fact, studies on humans confirm the indispensable role of essential fatty acids on learning. Infants deprived of Omega-3 fatty acid exhibit lower performance in neurodevelopment tests (1.) The study on ROS in rats suggests that essential fatty acids are critical not only in developmental learning but also in sensory input and stimulus response throughout the nervous system.

Since learning is the input and processing of sensory data, the assertion that ideal building blocks for biological machinery can improve learning follows logically. After all, it is only after we have received an input— a photon, a sound wave, touch— that we can respond. Although the effect of food on our nervous system is not as observable as that of drugs we should not overlook its importance. The studies are in and the essential fatty acid health trend is not unfounded. If we care about the health and ability of our minds then we have to provide our brains with building blocks that facilitate optimal functioning.

So, what do you say? I say pass the salmon.

References

1) Niu, S.L., Mitchell, D.C., Lim, S.Y., Wen, Z.M., Kim, H.Y., Salem, N.Jr., and Litman, B.J. "Reduced G Ptotein-coupled Signaling Efficiency in Retinal Rod Outer Segments in Response to n-3 Fatty Acid Deficiency-*." JBC Online (http://www.jbc.org/cgi/content/full/279/30/31098#FIG2) (2004): 1-14. 2) Omega3 Information Service home page 3) Stryer, Lubert. Biochemistry. New York: W.H. Freeman and Company, 1995. 4)American Heart Association , Fish and Omega3 Fatty Acids. 5) Omega-3 Fatty Acids and Arthritis Prevention and Remedy home page , 6) HOPES Glossary home page , from Stanford University. 7)Biology Lecture Notes , from the University of Connecticut. 8)Psychology Today , Food n Mood homepage.


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