herring oil
Also known as: Clupea harengus oil, Clupeidae oil, marine oil, Herring oil
Overview
Herring oil is a marine oil supplement extracted from the tissues of herring (Clupea harengus), a fatty fish found abundantly in the North Atlantic and Baltic Sea. It is a concentrated natural source of long-chain omega-3 polyunsaturated fatty acids (PUFAs), primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are the two most clinically relevant omega-3 fatty acids. This supplement is primarily used to increase dietary intake of EPA and DHA, aiming to support cardiovascular health, modulate lipid profiles, and exert general anti-inflammatory effects. Herring oil typically contains 18–30% combined EPA and DHA, with ratios varying based on processing and source, and may also include other fatty acids and fat-soluble vitamins. While research on herring oil specifically is moderate, with several randomized controlled trials (RCTs) and at least one systematic review/meta-analysis, its benefits are largely extrapolated from the more extensive literature on generic fish oil and omega-3 supplements. The evidence for its cardiovascular and lipid effects in humans is generally robust, though less is known about its impact on glycemic control or non-cardiovascular outcomes.
Benefits
Herring oil offers several evidence-based benefits, primarily due to its rich content of EPA and DHA. A key primary effect, quantified in an RCT, showed that daily supplementation with herring oil (250 mg EPA + DHA) significantly increased the erythrocyte omega-3 index from 5.1% to 10.7% (a 112% increase in EPA + DHA, p < 0.01) over 12 weeks. This clinically meaningful shift moved most participants from a “high risk” to a “low/intermediate risk” cardiovascular category based on this surrogate marker. Secondary effects, largely inferred from broader omega-3 research, include modest reductions in blood pressure, with optimal effects observed at 2–3 g/day EPA+DHA, particularly in hypertensive individuals. Animal studies also suggest herring oil may lower cholesterol concentrations, though human data are currently lacking. Benefits are more pronounced in populations with low fish intake or elevated cardiovascular risk, such as those with hypertension or hyperlipidemia. While the increase in omega-3 index is rapid (within weeks), maximal clinical benefits, such as reduced cardiovascular events, likely require sustained intake over months to years. The evidence quality is generally robust for cardiovascular and lipid effects, though specific herring oil studies are fewer than for general fish oil.
How it works
Herring oil exerts its effects primarily through its EPA and DHA content. These omega-3 fatty acids are incorporated into cell membranes, altering membrane fluidity and influencing the function of various receptors. They competitively inhibit the production of pro-inflammatory eicosanoids derived from omega-6 fatty acids, leading to a reduction in overall inflammation and improved vascular function. This mechanism contributes to its cardiovascular benefits, including lipid modulation and blood pressure regulation. EPA and DHA also interact with key molecular targets such as cyclooxygenase (COX), lipoxygenase (LOX), peroxisome proliferator-activated receptors (PPARs), and G protein-coupled receptors (e.g., GPR120). Herring oil's EPA and DHA are well absorbed, especially when consumed with meals, and their bioavailability is comparable to other marine oils.
Side effects
Herring oil is generally well tolerated at standard doses, with its safety profile largely extrapolated from broader fish oil and omega-3 supplement research. The most common side effects, affecting over 5% of users, are mild gastrointestinal symptoms such as a fishy aftertaste, nausea, or diarrhea. Uncommon side effects (1–5%) include rare allergic reactions, particularly with less purified oils, and a mild bleeding tendency, especially at very high doses. Rare side effects (less than 1%) can include severe hypersensitivity reactions or clinically significant bleeding, particularly when combined with anticoagulant medications. Potential drug interactions exist with anticoagulants and antiplatelets, where high-dose herring oil could theoretically increase bleeding risk, necessitating monitoring. Contraindications include known fish allergies (unless the oil is highly purified) and active bleeding disorders. In special populations, such as pregnant or lactating individuals, herring oil is considered safe at standard doses, consistent with general omega-3 safety guidelines.
Dosage
For increasing the omega-3 index, a minimum effective dose of 250 mg EPA + DHA daily has been shown to be significant. For broader cardiovascular and blood pressure benefits, optimal dosage ranges from 2–3 g EPA + DHA daily, based on meta-analyses of omega-3 supplements. Doses higher than 3 g/day generally do not confer additional benefits and may increase the risk of side effects. The maximum safe dose is typically considered up to 4 g/day EPA + DHA, though exceeding 3 g/day offers no additional benefit for most outcomes. Herring oil should ideally be taken with meals to enhance absorption and minimize gastrointestinal side effects. Softgel capsules are the standard form, but liquid options are also available. Absorption is improved by dietary fat, and enteric-coated capsules may further reduce GI discomfort. No specific cofactors are required for its efficacy.
FAQs
Is herring oil safe for daily use?
Yes, herring oil is generally safe for most healthy adults when taken at recommended doses. Mild gastrointestinal upset is the most common side effect, and serious adverse events are rare.
How long does it take to see benefits from herring oil?
You may see an increase in your omega-3 index within weeks. Clinical benefits like modest blood pressure or lipid improvements typically develop over several months of consistent supplementation.
Is more herring oil always better for health?
No, taking more than 3 grams of EPA + DHA daily from herring oil does not provide additional health benefits for most outcomes and may increase the risk of side effects like bleeding.
Can herring oil interact with medications?
Herring oil can theoretically increase the risk of bleeding when taken with anticoagulant or antiplatelet medications. Consult your doctor if you are on such medications.
How does herring oil compare to other fish oils?
Herring oil provides EPA and DHA similar to other marine oils. Its specific fatty acid profile and sustainability aspects might differ, but its core benefits are comparable to other quality omega-3 sources.
Research Sources
- https://amscd.termedia.pl/Herring-oil-intake-results-in-increased-levels-of-omega-3-fatty-acids-in-erythrocytes,82096,0,2.html – This randomized controlled trial by Stankova et al. (2018) investigated the effect of daily herring oil supplementation (250 mg EPA + DHA) on the omega-3 index in 83 subjects over 12 weeks. The study found a significant increase in erythrocyte omega-3 content, raising the omega-3 index from 5.1% to 10.7%, which moved most participants into lower cardiovascular risk categories. This well-conducted study provides strong evidence for herring oil's efficacy in improving omega-3 status, though it focused on a surrogate endpoint.
- https://www.ahajournals.org/doi/10.1161/JAHA.121.025071 – Zhang et al. (2022) conducted a dose-response meta-analysis of 71 RCTs on omega-3 supplementation and blood pressure. They identified a J-shaped dose-response, with optimal blood pressure reduction at 2–3 g/day of EPA + DHA, and no additional benefit above 3 g/day. This high-quality meta-analysis, while not specific to herring oil, provides robust evidence for the effective dosage range of omega-3s for blood pressure management, particularly in hypertensive and hyperlipidemic populations.
- https://pmc.ncbi.nlm.nih.gov/articles/PMC11531938/ – This animal study by Rimmen et al. (2024) compared the effects of herring oil and anchovy oil in type 2 diabetic rats. The research indicated that herring oil was effective in lowering cholesterol concentrations in this model, though it did not show effects on glucose levels or liver weight. While providing mechanistic insights, the direct human relevance of these findings, particularly regarding cholesterol, requires further investigation through human trials.
