Folks who routinely take fish oil may feel confused by a recent review of selected clinical studies, which questioned the value of that habit.

Two weeks ago, we addressed its misleading conclusions, which claimed there's insufficient clinical evidence that omega-3 fish oil lowers risks for heart disease, heart attacks, or stroke.

But its authors downplayed the very positive outcomes of two large clinical trials and emphasized clinical trials with negative outcomes — some of which involved patients who were already taking statins or other heart drugs, making any heart-benefits of fish oil hard to detect.

To read our critique of that review, see Report Doubts Heart Value of Fish Oil vs. Fish, in which we noted that other evidence reviews have produced distinctly positive conclusions. For example, see Do Fishy Omega-3s Really Cut Heart Risks?.

Most media reports about the recent evidence review took its conclusions at face value, ignoring the very large body of evidence that supports the cardiovascular value of fish oil.

And that supportive evidence just grew, thanks to a study whose positive, groundbreaking findings highlight the value of getting your blood tested for its levels of omega-3 fatty acids.

As we’ll explain, it’s also important to know your levels of omega-6 fatty acids — which most blood tests don’t cover.

New study supports the preventive-health value of omega-3s
The new paper was funded by the National Institutes of Health and comes from researchers at Harvard Medical School, Boston University, two South Dakota universities, and the Global Organization for Omega-3 EPA and DHA (Harris WS et al. 2018).

Lead author William S. Harris, Ph.D. — a biochemist from the University of South Dakota — is also the cofounder of OmegaQuant Analytics, LLC, which produces the blood test used in the study.

The link between higher omega-3 blood levels — as measured by Dr. Harris' Omega-3 Index test — and lower risk for death has been reported in many prior studies.

And there's good evidence that when omega-3s constitute 8% or more of the fats in red blood cells, you're significantly less likely to suffer from heart disease or heart-related adverse events.

Conversely, when omega-3s constitute 4% or less of the fats in your red blood cells, you run a significantly higher risk of heart disease and adverse heart events like heart attacks.

The research team analyzed blood-test data collected from 2,500 adults participating in the Framingham Heart Study Offspring study.

Most of the participants in that study — average age of 66 years, with a few more women than men — were born to parents who’d participated in the original, world-famous Framingham Heart Study.

All the volunteers were free of known cardiovascular disease (CVD) at the outset, and the study followed them for an average of seven years.

The goal was to compare people’s omega-3 blood levels and cholesterol profiles to their risk for death from any cause, including heart disease — and adjust the results to eliminate the effects of factors proven to influence the risk for death and heart disease.

That comparison showed that the volunteers with the highest blood levels of omega-3s — the so-called “omega-3 index” were about one-third less likely to have died from any cause, compared to those who had the lowest levels.

And having a higher Omega-3 Index was linked to enjoying a lower risk for any adverse heart- or cardiovascular-related event, such as a heart attack or stroke.

Interestingly, the causes of death most strongly reduced by having a low Omega-3 Index were those aside from cardiovascular disease or cancer — a finding which suggests that the beneficial effects of seafood-source omega-3s (EPA and DHA) cover many pathological processes.

Omega-3 Index beat cholesterol levels as a risk predictor
The authors of the new study also compared the risk-reduction benefits of the participants’ cholesterol levels as well as their omega-3 levels.

And it turned out that the participants’ Omega-3 Indices were better predictors of their heart -related health risks, versus their cholesterol levels and cholesterol profiles.

As Dr. Harris said, “We all know that the serum [blood] cholesterol level is a major risk factor for CHD [coronary heart disease], and since the latter is a major cause of death in the Western world, it would be reasonable to expect that a high cholesterol level would portend higher risk for premature death.”

However, as he said, “When baseline serum [blood] cholesterol levels were substituted for the Omega-3 Index … [cholesterol levels were] not significantly associated with any of the tracked outcomes, whereas the [Omega-3 Index] was related to 4 of the 5 [adverse] outcomes assessed."

The ideal: Test your omega-6 and omega-3 levels at the same time
It’s clear that the Omega-3 Index measured by Dr. Harris’s test has tremendous value for gauging the risk for heart trouble.

However, it's even better to also know your blood levels of omega-6 fatty acids in proportion to your omega-3 levels: the so-called “omega ratio”.

We learned about this little-known ratio and its importance from leading omega-3/health researchers.

These experts include former NIH advisor William E. Lands, Ph.D. —  one of the most published fatty acid scientists in the world — and NIH clinical psychiatrist Joseph Hibbeln, M.D., who’s conducted landmark studies on the effects of fish and omega-3s on child development and mood disorders.

Their research persuasively shows that it’s the combination of omega-6 and omega-3 levels that provide the best predictor of someone’s risk for heart disease.

For more on this topic, see our Omega-3/6 Balance: Hidden Health Risk page, which contains the Out of Balance video featuring interviews with leading experts, Report Finds Americans Need More Omega-3s ... and Far Fewer Omega-6s, America's Sickening Omega Fats Imbalance, Heart Risks Raised by Omega-6 Excess, and the research reports in the Omega-3/Omega-6 Balance section of our newsletter archive, which document the broad negative effects of American’s excessive intake of omega-6 fatty acids.

We partnered with biochemist Douglas Bibus, Ph.D. to devise the at-home Vital Omega 3/6 test, which measures the levels of both families of fatty acids. Dr. Bibus was chief lab assistant to the late Ralph Holman, Ph.D., the scientist who discovered and named omega-3 fatty acids.

The results of that test reveal a person’s omega-6 and omega-3 blood levels — as well as the levels of many other fatty acids — and reveals the meaning of the ratio of omega-6 and omega-3 fatty acids in your blood, in terms of heart risk.



  • Mozaffarian D, Lemaitre RN, King IB, Song X, Spiegelman D, Sacks FM, Rimm EB, Siscovick DS. Circulating long-chain ω-3 fatty acids and incidence of congestive heart failure in older adults: the cardiovascular health study: a cohort study. Ann Intern Med. 2011 Aug 2;155(3):160-70. doi: 10.7326/0003-4819-155-3-201108020-00006.
  • Harris WS, Pottala JV, Lacey SM, Vasan RS, Larson MG, Robins SJ. Clinical correlates and heritability of erythrocyte eicosapentaenoic and docosahexaenoic acid content in the Framingham Heart Study. Atherosclerosis. 2012 Dec;225(2):425-31. doi: 10.1016/j.atherosclerosis.2012.05.030. Epub 2012 Jun 7.
  • Harris WS, Tintle NL, Etherton MR, Vasan RS. Erythrocyte long-chain omega-3 fatty acid levels are inversely associated with mortality and with incident cardiovascular disease: The Framingham Heart Study. J Clin Lipidol. 2018 Mar 2. pii: S1933-2874(18)30061-8. doi: 10.1016/j.jacl.2018.02.010. [Epub ahead of print]
  • Marklund M, Leander K, Vikström M, Laguzzi F, Gigante B, Sjögren P, Cederholm T, de Faire U, Hellénius ML, Risérus U. Polyunsaturated Fat Intake Estimated by Circulating Biomarkers and Risk of Cardiovascular Disease and All-Cause Mortality in a Population-Based Cohort of 60-Year-Old Men and Women. Circulation. 2015 Aug 18;132(7):586-94. doi: 10.1161/CIRCULATIONAHA.115.015607. Epub 2015 Jun 17.