The Cooper Institute

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH


The Omega-3 Index: A Novel Way to Determine Cardiovascular Risk

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Eat better

Friday, Oct 14, 2016

Health behaviors such as diet play an important role in determining our long-term health status. An often misunderstood component of diet is the role of fat. Dietary fat is essential for human survival because the body cannot make certain types of fat that are needed. These include the omega-3 and omega-6 polyunsaturated fats; in particular linolenic and linoleic acid, respectively. Over the past 3 decades, convincing evidence has accumulated regarding the benefits of omega-3 polyunsaturated fats on cardiovascular health. Omega-3’s are sometimes referred to as ‘fish oils’ because they are found in high concentration among fatty fish such as salmon, herring, and mackerel, as well as in fish oil supplements. The benefits of omega 3’s on resting heart rate, resting blood pressure, and blood triglyceride levels have been clearly documented. There is also evidence that omega-3’s help to prevent inflammation, heart attack, stroke, cardiac arrhythmias, and sudden cardiac death.

There are actually three different omega-3 fats; alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).  While ALA is found in plant-based foods such as nuts and seeds, EPA and DHA are found in fatty fish. While all three types of omega-3’s are beneficial to our heart health, the evidence is a bit stronger for EPA and DHA. So, for the past several years organizations such as the American Heart Association have been recommending that individuals consume at least 2 servings per week of fatty fish in order to improve heart health.

In recent years, a blood test called the Omega-3 Index was developed by Dr. William Harris, an internationally known expert on omega-3 fatty acids and cardiovascular health. The index shows what percentage of the total amount of fatty acids in red blood cells are EPA and DHA. For example, if 7% of the fatty acids in red blood cells are EPA and DHA, the Omega-3 Index is 7%. Because fish intake in the U.S. is relatively low, the average Omega-3 Index is only ~4-5%. In countries where a greater amount of fish is consumed, the Omega-3 Index is much higher. For example, the Japanese typically have an index of ~9-10%.  Accumulating evidence shows that the index is strongly and inversely associated with cardiovascular outcomes. In other words, individuals with higher indexes tend to have significantly lower cardiovascular risk than individuals with lower indexes. Most experts feel that an index >8% is optimal for cardiovascular health, while an index of <4% is typically regarded as a state of dietary omega-3 deficiency. This is supported by data from many studies. For example, a paper on the index and acute coronary syndrome (ACS) was published in a leading medical journal (Block, Harris, Reid, Sands & Spertus, 2008).  ACS is an umbrella term for conditions where the heart muscle is not receiving sufficient oxygen. The authors compared index values for 768 ACS patients and 768 control subjects who were matched for age, gender, and race. Subjects were divided into three categories based on their index; low (<4%), intermediate (4.1-7.9%), and high (>8%).  Compared to the low index group, the odds for an ACS event were 42% lower in the intermediate group; and 69% lower in the high index group (Figure 1). Thus, a low index was found to be significantly associated with increased risk for ACS.
The number of labs that are able to measure the Omega-3 Index is very small at the current time. The Cooper Clinic has been routinely measuring the index on patients for the past several years by sending the samples to Dr. Harris’ lab for analysis. Along with additional blood work, a maximal treadmill exercise test, health history, a complete physical examination, and measures of coronary artery calcium, Cooper Clinic physicians are able to get an in-depth cardiovascular risk profile on their patients.

The bottom line is that most Americans would benefit greatly by increasing their intake of fatty fish to at least two servings per week. For individuals who are unable to meet this recommendation, a high quality fish oil supplement such as Cooper Complete™ can help bridge this gap.

To learn more about changing unhealthy behaviors such as poor diet, take The Cooper Institute’s Coaching Healthy Behaviors course. For the latest information on nutrition and health, take our Nutrition for Health and Fitness course (live or online). You need not be a fitness professional to attend our courses; everyone is always welcome.

Block, R. C., Harris, W. S., Reid, K. J., Sands, S. A., & Spertus, J. A.  EPA and DHA in blood cell membranes from acute coronary syndrome patients and controls. (2008). Atherosclerosis, 197(2), 821-828.