The year 2018 witnessed some landmark research on omega-3 fatty acids and heart disease.

Following some negative but flawed studies — whose shortcomings were obvious to experts — the results of two large clinical trials vindicated the heart-health value of omega-3s.

For more about those strikingly positive studies, see Omega-3s’ Heart Value Vindicated in Long, Large Clinical Trial and Omega-3s Score 2nd Big Heart Win.

And, earlier in 2018, we reported on a re-analysis of data from the famed Framingham Heart Study in Omega-3 Levels Beat Cholesterol at Predicting Death Risk.

The lead author of that report was William S. Harris Ph.D., of the University of South Dakota and the American Heart Association, co-inventor of the Omega-3 Index test at the center of the new study — you’ll see our discussion of that test and the equally valuable Omega-3/6 Balance test below, under “Background to the new study”.

Study finds most Americans falls short of omega-3 heart-health minimums
New research suggests that most of us need to do more to get enough omega-3s to protect the heart (Jackson KH et al. 2018).

The study was conducted by a team that included Dr. Harris, his daughter Kristina Harris Jackson, Ph.D., R.D., and researchers from Pennsylvania State University, the University of South Dakota, Indiana’s Dordt College, and OmegaQuant.

(OmegaQuant was founded by Dr. Harris to provide the Omega-3 Index test and employs Dr. Jackson. The at-home Vital Omega-3/6 HUFA Test™ reveals both your Omega-3 Index and Omega-3/6 Balance.)

According to Dr. Jackson, who served as lead researcher, the goal of their study was to determine which combination of (non-fried) fish intake and omega-3 supplements is likely to produce a cardio-protective Omega-3 Index level of 8% or above.

Coincidentally, we just published a report about the serious downsides of fried fish and other fried foods: see Going from the Fry Pan to an Early Grave. Those negatives explain why the study team specified intake of non-fried fish.

The Omega-3 Index is a measure of the amount of seafood-source omega-3s — specifically, EPA and DHA — in a person’s blood.

Having an Omega-3 Index of 4% or below is a risk factor for coronary heart disease and fatal heart attacks, while an index of 8% or above is strongly associated with reduced risks for coronary heart disease and heart attacks.

Dr. Jackson and her team measured the blood levels of omega-3 EPA and DHA in 3,458 people and surveyed them about their fish and fish oil intakes.

Unsurprisingly, the people who reported eating no fish intake and taking no omega-3 supplements had an average Omega-3 Index of about 4.1% — which approximates the average, significantly deficient level found in most Americans.

In contrast, people who reported taking a fish oil supplement and eating three fish meals a week enjoyed an average Omega-3 Index of 8.1%, which is strongly linked to protection of heart health.

Official fish-intake guidelines don’t do the job
The results of the new study suggest that official seafood intake guidelines for Americans aren’t robust enough to raise blood levels to a protective level:

  • The 2015-2020 Dietary Guidelines for Americans recommend eating about 8 ounces of a variety of seafood per week, which equates to about 250mg of omega-3 EPA and DHA mg per day.
  • The American Academy of Nutrition and Dietetics recommends eating two or more servings of fatty fish per week, which equates to about 500mg of omega-3 EPA and DHA per day.
  • The American Heart Association (AHA) recommends eating 1-2 seafood meals per week. Until 2018, the AHA guidelines specified “oily” fish, because they are higher in omega-3s. Removal of that specification recommending oily fish (such as sardines, tuna, and salmon) was unfortunate and unwarranted.  And, as Dr. Jackson said, “The AHA currently recommends two fish meals per week and it does not recommend supplementation. In light of our findings, this regimen is unlikely to produce a cardioprotective Omega-3 Index of 8%.”

It’s important to remember that DHA and EPA — especially DHA — are essential to human life and health, and the only food sources are fish, shellfish, and algae.

The human body can use the plant-source omega-3 fatty acid called ALA to make very small amounts of EPA, and even smaller amounts of DHA.

The only significant sources of omega-3 ALA — in rough descending order from highest to lowest levels — are flaxseed oil, flaxseed, canola oil, soybean oil, walnuts, hemp seed, chia seed, dark, leafy greens and avocados.

Background to the new study: The Omega-3 Index and Omega-3/6 Balance
Recent years have seen the development of various ways to link a person’s levels of various fatty acids to their risk for heart disease and adverse outcomes such as heart attacks.

One such measure is the omega-3/omega-6 blood-level measure developed by renowned fatty acid researcher professor William E. Lands, Ph.D., a former senior scientific advisor to the National Institutes of Health.

Dr. Lands discovered that having high blood levels of omega-6 fatty acids relative to omega-3 levels — which is characteristic of most Americans — raises heart risks.

Americans have unhealthful omega-3/6 ratios in their blood because they consume large amounts of certain vegetable oils — corn, soy, safflower, sunflower, cottonseed — that are very high in omega-6 fatty acids and contain either no omega-3s or only low levels.

(To learn more about the importance of the dietary balance between omega-3 and omega-6 fats, see our Omega-3/6 Balance page, which hosts the “Out of Balance” video featuring interviews with leading experts, including Dr. Lands.)

Then, in 2007, Dr. William Harris collaborated with German cardiologist Clemens von Shacky to develop a measure of heart risk called the “omega-3 index”.

Studies by Drs. Harris and von Shacky revealed the Omega-3 Index as a reliable predictor of heart disease risk, and their work has been validated by independent research teams.

The Omega-3 Index has become a widely accepted measure of risk for coronary heart disease and heart attacks, and for someone’s intake of seafood-source omega-3s from fish, shellfish, and/or fish oil supplements.

The Omega-3 Index test measures the percentage of omega-3 fatty acids in your blood — specifically, the percentage of omega-3 DHA and EPA in your red blood cells (RBCs).

Compelling evidence links omega-3 RBC levels of 4% or less to a relatively high heart risks, and links omega-3 RBC levels of 8% or more to relatively low heart risks.

One of the recent, highly positive clinical trials tested an EPA-only prescription fish oil supplement (Vascepa), and the other trial tested a prescription supplement that was somewhat higher in EPA than DHA (Omacor).

Nonetheless, a recent study by Dr. Harris and others showed that — compared with higher intakes of EPA — higher intakes of DHA were more effective at raising the Omega-3 Index (Allaire J et al. 2017).

To learn your Omega-3 Index and Omega-3/6 Balance, you can take the at-home Vital Omega-3/6 HUFA Test™.


  • Allaire J, Harris WS, Vors C, Charest A, Marin J, Jackson KH, Tchernof A, Couture P, Lamarche B. Supplementation with high-dose docosahexaenoic acid increases the Omega-3 Index more than high-dose eicosapentaenoic acid. Prostaglandins Leukot Essent Fatty Acids. 2017 May;120:8-14. doi: 10.1016/j.plefa.2017.03.008. Epub 2017 Mar 31.
  • Jackson KH, Polreis JM, Tintle and Al, Kris-Etherton PM, Harris WS. Association of reported fish intake and supplementation status with the omega-3 index. Prostaglandins Leukot Essent Fatty Acids. Volume 142, March 2019, Pages 4-10