VUlogo

Psychology Department

Health Psychology Home Page

Papers written by students providing scientific reviews of topics related to health and well being

  HomeWeight LossAlternative Therapy | Supplements | Eating Disorders | Fitness | About this Page |

 

Fish Oil and Heart Health

Elise Russo

October 24th, 2008

 

Introduction

Due to the recent rise in popularity of dietary supplements of all kinds, people everywhere have become obsessed with figuring out that “dream pill,” the drug that will keep them healthy without having to make drastic lifestyle changes.  One of the most widely touted supplements nowadays is the omega-3 fatty acid “fish oil” pill.  All over the news as well as in advertisements and on drugstore shelves, fish oil has become a hot commodity.  Everyone has heard that somehow, these pills are “good for you,” but do many people really know why? Does fish oil, in supplement form or consumed directly from fish, have any positive effects on cardiovascular health?

 

 

Omega-3 Fatty Acids: What Are They, and How Are They Related to Fish Oil?

            A fatty acid is defined as “one of many molecules that are long chains of lipid-carboxylic acid found in fats and oils and in cell membranes as a component of phospholipids and glycolipids,” (http://www.medterms.com/script/main/art.asp?articlekey=15385).  Omega-3 fatty acids belong to a group known as “essential fatty acids.”  This means that “they are essential to human health but cannot be manufactured by the body,” and therefore they “must be obtained from food,” (http://www.umm.edu/altmed/articles/omega-3-000316.htm).  There are three different kinds of omega-3 fatty acids: “There are the fish oils, which contain docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA.) Then there are the plant sources with alpha-linolenic acid (ALA), which is converted into omega-3 fatty acids in the body,” (http://www.webmd.com/diet/vitamins-supplements-8/supplement-guide-omega-3-fatty-acids).  The effects of fish oil omega-3 fatty acids have been studied more extensively than the plant fatty acid ALA.  When people eat fish, and in particular, fatty fish such as tuna, salmon, or mackerel, they obtain these essential omega-3 fatty acids, which are necessary for normal body function.  In recent years, the taking of omega-3 fatty acid pills (fish oil pills) has become very popular due to many studies showing that supplementing your diet with omega-3 fatty acids from fish oil can improve heart health as well as health in general.  While some of these claims are unfounded, there has been a lot of research done surrounding fish oil’s influence on heart health, so what exactly are the claims being made about fish oil in connection with heart health? 

 

Omega-3 Fatty Acids from Fish Oil and The Heart: How Does It Help?

            The American Heart Association states at the top of its website, “Omega-3 fatty acids benefit the heart of healthy people, and those at high risk of — or who have — cardiovascular disease,” (http://www.americanheart.org/presenter.jhtml?identifier=4632).  According to the Mayo Clinic, “Cardiovascular disease is a broad term used to describe a range of diseases that affect your heart or blood vessels,” (http://www.mayoclinic.com/health/cardiovascular-disease/HB00032).  There are a variety of diseases that affect the health of the heart, and studies have shown that some cardiovascular diseases are more clearly and definitively affected by the omega-3 fatty acids found in fish oil: “Evidence from several studies has suggested that amounts of DHA and EPA in the form of fish or fish oil supplements lowers triglycerides, slows the buildup of atherosclerotic plaques (‘hardening of the arteries’), lowers blood pressure slightly, as well as reduces the risk of death, heart attack, dangerous abnormal heart rhythms, and strokes in people with known heart disease,” (http://www.mayoclinic.com/health/fish-oil/NS_patient-fishoil).   The American Heart Association’s website says that “the link between omega-3 fatty acids and CVD risk reduction are still being studied, but research has shown that omega-3 fatty acids decrease risk of arrhythmias, which can lead to sudden cardiac death, decrease triglyceride levels, decrease growth rate of atherosclerotic plaque, and lower blood pressure (slightly),” (http://www.americanheart.org/presenter.jhtml?identifier=4632).  It recommends that everyone eats fatty fish at least two times a week, and even specifies how intake should be adjusted for the type of heart disease a person has:

Patients without documented coronary heart disease (CHD)

Eat a variety of (preferably fatty) fish at least twice a week. Include oils and foods rich in alpha-linolenic acid (flaxseed, canola and soybean oils; flaxseed and walnuts).

Patients with documented CHD

Consume about 1 g of EPA+DHA per day, preferably from fatty fish.  EPA+DHA in capsule form could be considered in consultation with the physician. 

Patients who need to lower triglycerides 

2 to 4 grams of EPA+DHA per day provided as capsules under a physician’s care. 

 (http://www.americanheart.org/presenter.jhtml?identifier=4632). 

Now that the issues have been defined, it remains to be seen exactly what evidence there is to prove these claims. 

 

Who Says It’s True?

        In 2002, the American Heart Association issued an official statement that said that “important new findings, including evidence from randomized controlled trials (RCTs), have been reported about the beneficial effects of omega-3 (or n-3) fatty acids on cardiovascular disease (CVD) in patientswith preexisting CVD as well as in healthy individuals,” (Kris-Etherton, Harris, and Appel 2002, page 2747).  In 2004, the U.S. Department of Health and Human Services’ Agency for Healthcare Research and Quality said, “The systematic reviews of the available literature found evidence that long chain omega-3 fatty acids, the beneficial component ingested by eating fish or taking a fish oil supplement, reduce heart attack and other problems related to heart and blood vessel disease in persons who already have these conditions, as well as their overall risk of death. Although omega-3 fatty acids do not alter total cholesterol, HDL cholesterol, or LDL cholesterol, evidence suggests that they can reduce levels of triglycerides—a fat in the blood that may contribute to heart disease,” (http://www.ahrq.gov/news/press/pr2004/omega3pr.htm).  According to these two reputable sources, omega-3 fatty acids, particularly from fish oil, are beneficial to people without symptoms of heart disease, people who are predisposed to heart disease, and people with documented cases of heart disease.  So, whether someone has none or all of the risk factors for heart disease, or heart disease in some form itself, according to these and many other sources, omega-3 fatty acids can help keep a person healthier.  It is not only the American Heart Association and the AHRQ who give reasoning for eating more fish and taking more supplements, but also user-friendly websites such as WebMD, Medline, The Mayo Clinic Online, etc.  All are places where people go to find useful and helpful tips on how to stay healthy.  Where is all the research to prove what all of these websites and government organizations are saying?

Research: Give Us Some Evidence

            In 1976, the scientists Bang, Dyerberg, and Sinclair studied the composition of northwestern Greenland Eskimo food in comparison with Danish food, and discovered that Eskimo’s ate a lot of foods high in omega-3 fatty acids, where as Danes ate a lot of foods high in the less-healthy omega-6 fatty acids (1980, page 2657).  They performed this study because of an analysis done in 1970 that showed that this particular population of Eskimos had only a 3.5% death rate from ischemic heart disease, and they found that “the rarity of ischemic heart disease in Greenland Eskimos may partly be explained by the antithrombotic effect of the long-chained polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA) prevalent in diets rich in marine oils,” (Bang, Dyerberg, and Sinclair 1980, page 2657).  To clarify, ischemic heart disease is “the term given to heart problems caused by narrowed heart arteries. When arteries are narrowed, less blood and oxygen reaches the heart muscle. This is also called coronary artery disease and coronary heart disease. This can ultimately lead to heart attack,” (http://www.americanheart.org/presenter.jhtml?identifier=4720).  So, basically, this study proved that the high-fish diet of these Eskimos was causing them to have drastically reduced heart disease rates.  It wasn’t until more recent years, however, that too many studies on the affects of fish oil’s omega-3’s began to appear. 

            Previously mentioned, the 2002 AHA Scientific Statement that gave the evidence for the American Heart Association’s stance advocating the consumption of fish containing omega-3 fatty acids at least twice a week claimed to have reviewed studies showing “that men who ate at least some fish weekly had a lower coronary heart disease (CHD) mortality rate than that of men who ate none,” as well as “that fish consumption favorably affects CHD mortality, especially nonsudden death from myocardial infarction (MI),” (Kris-Etherton, Harris, and Appel 2002, page 2747).  It appears that most of the observational studies performed concerning omega-3’s and heart health yielded positive results, meaning that small increases in intake of omega-3 fatty acids through supplements or eating fish will help maintain a healthier cardiovascular system.   

            A few Randomized Controlled Trials (RCTs) also took place concerning omega-3 fatty acids from fish oil and CVD.  The first trial, known as the DART trial, concluded that "a modest intake of fatty fish (2 or 3 portions per week) may reduce mortality in men who have recovered from myocardial infarction,” (Burr, Fehily, Gilbert, Rogers, Holliday, Sweetnam, Elwood, and Deadman 1989, page 759).  The largest trial, the GISSI-Prevention Trial, proved that fish oil consumption (1< g/d) is beneficial in a setting of secondary prevention of certain forms of CVD (Breslow 2006 page 1477S). 

            Epidemiological and clinical studies have shown that there are four mechanisms that can attempt to explain how omega-3 fatty acids from fish oil can benefit those suffering from CVD: “preventing arrhythmias, lowering plasma triacylglycerols, decreasing blood pressure, decreasing platelet aggregation, improving vascular reactivity, and decreasing inflammation,” (Breslow 2006 page 1478S).  All of these components are related to overall heart health, and omega-3 fatty acids from fish oil have been proven in some way to prevent everything from the harmful build-up of plaque in the arteries of the heart (atherosclerosis) to arrhythmias (the heart beating off-rhythm in some way). 

Too Good To Be True?

            Though the evidence is there to prove that omega-3 fatty acids from fish oil do in fact have a positive impact on cardiovascular health for a variety of people, some of the studies list a few confounding factors that also need to be taken into account: “people that have a high intake of fatty fish might have a healthier lifestyle in general,” (Brouwer, Geelen, and Katan 2006, page 357).  If people who are eating more fish or taking omega-3 fatty acid supplements are in general healthier than the rest of the population, it is not easy to measure whether or not fish oil really does have much of an influence on heart health.  Many scientists also believe that the evidence from trials is less clear than organizations such as the American Heart Association view it.  For certain specific situations of CVD, fish oil has not been proven to make any measurable or significant impact. 

 

Conclusion

            Though fish may not be everyone’s favorite meal, there is undeniable evidence that including more of it in your diet is far from harmful.  While the full effects of omega-3 fatty acids from fish oil are still being researched, there is definitely a good deal of evidence pointing towards its positive influences on keeping people’s hearts healthy.  This is one supplement that it could not hurt to take! 

 

Literature Cited

Bang, H. O., Dyerberg, J., Sinclair, H. M. The Composition of the Eskimo Food in North Western Greenland.  The American Journal of Clinical Nutrition, 33(12), 2657-2661.   

Breslow, Jan L. (2006).  n-3 Fatty Acids and Cardiovascular Disease.  The American Journal of Clinical Nutrition, 83(6), 1477S-1482S. 

Brouwer, I. A., Geelen, A., Katan, M. B. (2006).  n-3 Fatty Acids, Cardiac Arrhythmia and Fatal Coronary Heart Disease.  Progress in Lipid Research, 45, 357-367. 

Burr, M. L., Fehily, A. M., Gilbert, J. F., Rogers, S., Holliday, R. M., Sweetnam, P. M., et al. (1989).  Effects of Changes in Fat, Fish, and Fibre Intakes on Death and Myocardial Reinfarction: Diet and Reinfarction Trial.  The Lancet, 757-782. 

Kris-Etherton, P. M., Harris, W. S., Appel, L. J. (2002). Fish Consumption, Fish Oil, Omega-3 Fatty Acids, and Cardiovascular Disease.  Circulation 106, 2747-2757. 

“AHRQ Evidence Reports Confirm that Fish Oil Helps Fight Heart Disease.” Agency for Healthcare and Research Quality.  (2004).  Retrieved October 8th, 2008 from: http://www.ahrq.gov/news/press/pr2004/omega3pr.htm.

“Fish and Omega-3 Fatty Acids.” American Heart Association.  (2008).  Retrieved October 8th, 2008 from: http://www.americanheart.org/presenter.jhtml?identifier=4632.

“Omega-3 Fatty Acids.” University of Maryland Medical Center.  (2008).  Retrieved October 8th, 2008 from: http://www.umm.edu/altmed/articles/omega-3-000316.htm.

“Omega-3 Fatty Acids.” WebMD.  (2008).  Retrieved October 8th, 2008 from: http://www.webmd.com/diet/vitamins-supplements-8/supplement-guide-omega-3-fatty-acids.

“Omega-3 Fatty Acids, Fish Oil, Alpha-Linolenic Acid.”  Mayoclinic.com.  (2008).  Retrieved October 8th, 2008 from: http://www.mayoclinic.com/health/fish-oil/NS_patient-fishoil

“Omega-3 Fatty Acids, Fish Oil, Alpha-Linolenic Acid.” MedlinePlus.  (2008).  Retrieved October 8th 2008 from: http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-fishoil.html.

 

 

VUlogo

Psychology Department

The Health Psychology Home Page is produced and maintained by David Schlundt, PhD.
  

me

VuLogoVanderbilt Homepage

Return to the Health Psychology Home Page
Send E-mail comments or questions to Dr. Schlundt