Omega-6 and Myocarditis: A Genetic Signal, Not a Diet Rule

A new genetic analysis raises a narrow, interesting question: could higher circulating omega-6 polyunsaturated fatty acids increase myocarditis risk? The study found that genetically proxied omega-6 levels had a causal signal for myocarditis, while omega-3 levels showed no statistically significant effect on myocarditis, endocarditis, or pericarditis. That is more specific—and less useful for menu planning—than the usual "omega-3 good, omega-6 bad" story.

The finding does not show that eating a particular omega-6-rich food causes myocarditis. It does not justify cutting seed oils to prevent cardiac inflammation. It is one unreplicated Mendelian randomization study of a rare disease, with important unanswered questions about the genetic instruments and no accessible effect estimates. Treat it as a hypothesis worth testing, not a dietary diagnosis.

What the genetic study found

In a 2026 Mendelian randomization study by Song et al., researchers used genetic variants associated with circulating omega-3 and omega-6 PUFA levels in 115,006 people of European ancestry. They then tested whether those genetically proxied levels related to three cardiac inflammatory diseases in a 2021 European Bioinformatics Institute outcome dataset: endocarditis, myocarditis, and pericarditis.

The primary analysis used inverse-variance weighting, with weighted-median and MR-Egger analyses as checks. The authors required a statistically significant inverse-variance weighted result plus matching effect directions in both sensitivity analyses before calling a relationship causal. By that standard, omega-6 PUFAs showed a causal signal for higher myocarditis risk. Omega-3 PUFAs showed no statistically significant causal effect for any of the three outcomes.

The distinction matters. The analysis did not find a general effect of omega-6 on every form of cardiac inflammation, and it did not find that omega-3 prevents myocarditis. It found one disease-specific genetic association that passed the authors' causal criteria.

Readers should also know what the publication does not currently let us judge. Its accessible evidence does not report the odds ratio, confidence interval, p-value, instrument strength, variance explained, number of genetic variants, or myocarditis case count for this result. Without those numbers, nobody can estimate the size of the apparent risk increase, its precision, or its likely clinical importance.

Why Mendelian randomization is useful—and fallible

Conventional nutrition studies have a familiar problem: people who eat more of one nutrient often differ in many other ways. They may smoke less, exercise more, have different incomes, take medications, or change their diet after becoming ill. Mendelian randomization uses inherited genetic variants as proxies for a lifelong tendency toward higher or lower circulating nutrient levels. Because genes are assigned before most adult lifestyle choices, the design can reduce confounding and reverse causation.

It cannot turn every genetic association into a dietary prescription. The method depends on a hard-to-prove condition: the selected variants must affect myocarditis mainly through PUFA levels, rather than through another route. That condition is especially relevant here because PUFA-associated variants often cluster around FADS1 and FADS2, genes involved in fatty-acid metabolism that can also influence triglycerides, LDL cholesterol, HDL cholesterol, and inflammatory markers. If those pathways affect myocarditis independently of measured PUFA levels, the result may partly reflect genetic lipid biology rather than omega-6 exposure itself.

The available report does not allow readers to assess whether MR-Egger intercept testing or MR-PRESSO adequately addressed horizontal pleiotropy. Myocarditis also occurs at roughly 10 to 22 cases per 100,000 people annually in population studies. Rare outcomes can leave a genetic analysis with few confirmed cases and wide uncertainty, even when the exposure dataset is large.

The biology is plausible, but plausibility is not proof

Omega-6 PUFAs can contribute to arachidonic acid, a precursor for prostaglandins and leukotrienes. These signaling molecules can promote vasodilation, vascular permeability, and leukocyte recruitment—processes involved in inflammation. Omega-3 and omega-6 fats both feed into lipid-signaling pathways, so the biology is more complicated than a two-team sports rivalry.

There is also experimental evidence that omega-3 PUFAs can reduce inflammatory signaling in tissue near the heart. In an ex vivo study by Quarta et al., omega-3 treatment reduced pro-inflammatory cytokine expression through NRF2 and NF-κB pathway suppression in epicardial and pericardial adipose tissue from patients with atherosclerosis, as well as in adipose-derived stem cells.

That experiment supports the idea that omega-3s can affect inflammatory pathways in cardiac-adjacent tissue. It does not establish that omega-3 supplementation prevents myocarditis. Atherosclerotic adipose tissue differs from heart muscle inflamed by viral or immune-mediated myocarditis in its cells, triggers, and tissue environment. Human mechanism studies can illuminate a pathway without answering a clinical-endpoint question.

Other cardiovascular evidence does not settle myocarditis

Large omega-3 trials point in different directions for broader cardiovascular outcomes. As reviewed by Bae et al., REDUCE-IT found cardiovascular benefit with 4 grams per day of EPA-only icosapent ethyl in high-risk patients receiving statins, while STRENGTH found no benefit with an EPA-plus-DHA formulation. Neither trial measured myocarditis incidence.

Those results neither confirm nor refute the genetic null result for omega-3 and myocarditis. They do show that omega-3 effects can depend on formulation, dose, comparator, population, and endpoint. "Omega-3" is a nutrient category, not a guarantee stamped onto every clinical outcome.

The same endpoint problem applies to dietary-pattern trials. In the DASH-Sodium trial, a DASH eating pattern and sodium reduction were tested in adults with elevated blood pressure, using high-sensitivity troponin I, NT-proBNP, and GDF-15 as cardiac biomarkers. Those markers measure injury, strain, and inflammation-related processes; they are not diagnoses of myocarditis, pericarditis, or endocarditis. DASH also changes sodium, potassium, fiber, and other food components, so it cannot isolate a PUFA effect.

An unresolved contradiction

Song et al. acknowledge prior observational research in Circulation that associated omega-6 fatty acids with lower cardiovascular inflammatory markers—the opposite direction from their myocarditis signal. That conflict has several possible explanations. Observational studies can be distorted by confounding or diet changes after illness. The MR result could be more resistant to those biases, but it could also be distorted by pleiotropy or limited precision. The available evidence does not resolve which explanation fits best.

The study population also matters. The exposure and outcome data came from people of European ancestry, so the result may not generalize to populations with different genetic backgrounds, diets, infectious exposures, or myocarditis causes. No randomized trial or prospective cohort has yet tested measured PUFA levels against incident myocarditis, pericarditis, or endocarditis.

What to do with this finding

Do not change your diet specifically to prevent myocarditis on the basis of this study. The evidence identifies a plausible genetic signal, but it does not provide a verified risk estimate, independent replication, or trial evidence that changing omega-6 intake changes clinical risk.

For overall cardiovascular health, dietary-pattern evidence remains stronger. A 2025 umbrella review of Mediterranean diet trials included 18 meta-analyses covering 238 randomized controlled trials and concluded that the pattern benefits primary and secondary cardiovascular prevention. A separate meta-analysis in people with established cardiovascular disease found that each two-point increase in Mediterranean diet score was associated with lower all-cause mortality (hazard ratio 0.85; 95% CI 0.78 to 0.93) and lower cardiovascular mortality (hazard ratio 0.91; 95% CI reported in the study).

A Mediterranean-style pattern may change PUFA intake, but its evidence does not rest on one fatty-acid ratio. It includes foods, fiber, unsaturated fats, minerals, and eating habits that move together. The omega-6–myocarditis finding becomes actionable only if larger genetic studies replicate it, pleiotropy analyses hold up, prospective cohorts link biomarker levels to incident disease, and trials show that changing intake alters meaningful clinical outcomes.

Verdict: genetically higher omega-6 levels may increase myocarditis risk, but one incomplete and unreplicated Mendelian randomization result cannot tell you how much risk changes—or whether changing your diet changes it.