So you take a few fish oil capsules every day. You try to eat fish once or twice a week. But is that enough to take full advantage of the heart health benefits of omega-3 fatty acids? Is it enough to maximally reduce risk for heart attack and other cardiovascular events?

If you take fish oil capsules, what is the concentration of omega-3 fatty acids? How well are they absorbed? How effectively are the omega-3 fatty acids you absorb incorporated into cell membranes?

Even if you take fish oil supplements, it is hard to know how successful you‘ve been in increasing your blood levels. It is now possible to measure the amount of omega-3 fatty acids in your bloodstream and know just how much you have. Too little and you might still be at high risk for cardiovascular events. 

Omega-3 levels and sudden cardiac death

Two large studies, one from the University of Washington and the other from Boston, demonstrated that higher omega-3 blood (the level in red blood cells, or RBCs) levels were associated with reduced likelihood of sudden cardiac death. The risk for sudden cardiac death was 10-fold higher for the lowest omega-3 RBC levels compared to the highest.

What's the average omega-3 RBC level for Americans? Most Americans have omega-3 RBC levels in the 2.5-4.0% range. People with heart disease can have levels less than 1%. Some authorities propose that this new measure be called the omega-3 index. 

Subsequent studies have shown that the omega-3 index has greater power to discriminate who will have a heart attack or die from sudden cardiac death better than any other common laboratory measure of coronary risk, including LDL cholesterol, HDL cholesterol, triglycerides, total cholesterol to HDL ratio, homocysteine, and c-reactive protein.

Beyond the heart attack- and sudden cardiac death-reducing effects demonstrated in studies like the 11,000-participant GISSI Prevenzione Study, omega-3 fatty acids modify the properties of cell membranes, including those in heart muscle. Omega-3 fatty acids stabilize heart rhythm generation and therefore reduce abnormal rhythms like atrial fibrillation. Omega-3 fatty acids trigger a cascade of anti-inflammatory eicosanoids like prostacyclin and exert beneficial action on nuclear receptors that yield improved lipid metabolism. This results in reduced triglycerides, reduced blood pressure,  more relaxed arteries, and more stable plaque. 

What does the omega-3 index tell you? Just as hemoglobin A1c offers a 3-month look into blood glucose levels, the omega-3 index reflects your long-term omega-3 intake. The quantity of RBC omega-3s also closely parallels the quantity of omega-3s in heart tissues.

What is an ideal omega-3 index?

The above studies relating RBC omega-3 levels and sudden cardiac death suggest that a level of 6.3-7.3% is associated with far fewer fatal events¾but events are not eliminated at this level. Is there even greater benefit with levels higher than 6.3-7.3%?