Cetoleic Acid (Omega-11): A Comprehensive Reference
1. Identity and Chemical Characterization
Cetoleic acid is a 22-carbon fatty acid with a single cis double bond at position 11, belonging to the long-chain monounsaturated fatty acid (LC-MUFA) class. Its IUPAC name is (Z)-docos-11-enoic acid, and its shorthand lipid notation is C22:1 n-11. It is a linear very-long-chain fatty acid and belongs to the Omega-11 group. Cetoleic acid is a positional isomer of erucic acid, which is a closely related 22-carbon monounsaturated fatty acid but with its double bond at the omega-9 (Δ13) position. There is also an isomer with a Δ11 double bond in the trans-configuration, also present in nature, called cetoelaidic acid.
Cetoleic acid, known as 22:1 n-11, is a very-long-chain monounsaturated omega-11 fatty acid that is considered nearly insoluble in water and has a relatively neutral nature.
1.1 Natural Sources
Cetoleic acid occurs in both marine animal and plant-derived sources, though these differ in chemical form:
- Marine fish oils: Certain North Atlantic fish such as mackerel and herring have lower levels of EPA and DHA but high levels of long-chain monounsaturated fatty acids (LCMUFA C20–C22), of which the most abundant is cetoleic acid (C22:1 n-11), representing 10–22% of the total. Cetoleic acid is also present in the glycerol esters of some fish oils, with the concentration in cod liver oil reaching up to 12%. Cetoleic acid "is only found in North Atlantic pelagic fish species," including herring, mackerel, and sandeel.
- Plant-derived wax esters: The acid is present in the wax esters of jojoba oil at 15–20% and in avellana oil from the Chilean hazelnut (Gevuina avellana) at about 9–10%.
- Relative abundance in fish: Cetoleic acid is the most abundant LC-MUFA in relevant fish species, representing between 10% to 22% of the overall LC-MUFA content, followed by gadoleic acid and gondoic acid, depending on the type of fish.
1.2 Common Forms and Preparations
As a commercial dietary supplement, cetoleic acid is currently available predominantly as a constituent of standardized North Atlantic herring oil concentrates. A couple of companies are now commercializing cetoleic acid-rich fish oils. Grøntvedt Biotech announced it was developing such an oil in 2022 and launched it in 2023 under the brand name CETO3. CETO3 is produced by immediately processing fresh fish to oil in less than 30 minutes at the company's plant in Uthaug, Norway.
CETO3 Omega-11, combined with another long-chain omega-9 monounsaturated fatty acid, gondoic acid, and omega-3 fatty acids EPA and DHA, can be used in liquid applications or in capsules. A separate product, Epax Cetoleic 10, similarly comprises gondoic acid (omega-9) and cetoleic acid, an omega-11 marine lipid.
In its plant-derived form, cetoleic acid is found as part of the wax ester matrix of jojoba oil rather than as a free fatty acid or triglyceride. Jojoba "wax" is composed almost entirely (~97%) of mono-esters of long-chain fatty acids and alcohols, accompanied by only a tiny fraction of triglyceride esters.
2. Traditional and Historical Use
Cetoleic acid does not have a documented history of use as an isolated compound in any traditional medical system. As a single molecular species, it was not identified until the modern era of lipid chemistry. Its occurrence in the foods that traditional cultures consumed — particularly North Atlantic pelagic fish — is ancient, but the attribution of specific health properties to cetoleic acid specifically is a product of twentieth- and twenty-first-century science.
Dietary consumption through fish: Populations of Scandinavia, Iceland, and other North Atlantic coastal regions have consumed herring, mackerel, and related species as dietary staples for centuries. These fish are naturally high in cetoleic acid, meaning that traditional consumers of these foods were ingesting cetoleic acid as an integral component of their diet, long before its identity was known.
Jojoba plant use: Cetoleic acid occurs in jojoba oil, which itself has an indigenous history of use. The O'odham Native American tribe extracted the oil from jojoba seeds to treat sores and wounds. Jojoba seeds and oil have a long history of use in folklore to treat various ailments, such as skin and scalp disorders, superficial wounds, sore throat, obesity, and cancer; for improvement of liver functions, enhancement of immunity, and promotion of hair growth. However, these traditional applications relate to jojoba oil as a whole preparation; cetoleic acid's contribution to these traditional uses has not been specifically established in the scientific literature.
Early scientific interest in marine fish oils: Some early studies reported that fish oils rich in MUFA may have beneficial effects on coronary heart disease (CHD) in humans. These early investigations, preceding the isolation and characterization of cetoleic acid specifically, helped stimulate subsequent focused research.
3. Key Constituents, Active Compounds, and Mechanisms of Action
3.1 Classification Within Fatty Acid Biology
Long-chain monounsaturated fatty acids such as erucic acid, cetoleic acid, and gondoic acid are 20–22-carbon fatty acids with a double bond in their ω-9, ω-11, and ω-9 positions, respectively. Cetoleic acid is thus distinct from the well-studied omega-3 polyunsaturated fatty acids (EPA and DHA) and from common dietary monounsaturated fats like oleic acid (omega-9, C18:1). Its very long chain length (22 carbons) places it in a structural category with specific metabolic characteristics that differ from shorter-chain MUFAs.
3.2 Enhancement of ALA-to-EPA/DHA Conversion (Omega-3 Pathway Stimulation)
The most extensively studied mechanism of cetoleic acid is its ability to enhance the body's endogenous synthesis of the long-chain omega-3 fatty acids EPA and DHA from the plant-based precursor alpha-linolenic acid (ALA). Consumption of LCMUFAs may lead to increased conversion of α-linolenic acid (C18:3 n-3; ALA) to EPA and DHA, a process that is usually limited such that only 5–10% of ALA is converted to EPA and DHA.
Østbye and colleagues showed that cetoleic acid promotes the conversion of ALA to DHA and EPA in HepG2, a human hepatocyte-derived cell line, and to EPA in primary salmon hepatocyte cells. Specifically, increased endogenous levels of cetoleic acid led to increased production of radiolabeled EPA+DHA in HepG2 by 40% and EPA in salmon hepatocytes by 12%. In the DHA pathway specifically, cetoleic acid reduced the ratio EPA:DHA from 3:1 to 2:1 and increased 2-fold the production of DHA compared to control cells in human hepatocyte cultures.
The hypothesized mechanism underlying this effect involves the peroxisomal beta-oxidation pathway. MUFAs were assumed to increase the peroxisomal β-oxidation and thereby improve the synthesis of the health-promoting long-chain n-3 fatty acids. Peroxisomal β-oxidation is involved in the last step of the n-3 metabolic pathway, shortening 24:6n-3 to DHA. However, the precise enzymatic mechanism remains under investigation: cetoleic acid did not influence the activity of acyl CoA-oxidase in any of the cell types contrary to one of the hypotheses, though previous studies with rodents fed a diet based on MUFAs reported an increased EPA level and a slightly induced peroxisomal β-oxidation in liver.
In vivo animal corroboration was also provided: Atlantic salmon were fed four diets supplemented with either sardine oil low in cetoleic acid or herring oil high in cetoleic acid at two inclusion levels, with diets balanced for EPA+DHA content within the Low and within the High groups. The salmon were fed these diets from 110 g to 242 g. The level of EPA+DHA in liver and whole-body retention of DPA and EPA+DHA relative to what was eaten increased with increased dietary cetoleic acid levels. A follow-up rat study using camelina and sandeel oils found that utilisation of the plant-based omega-3 fatty acid ALA to EPA and DHA can be increased by combining dietary oils, one rich in ALA and the other rich in cetoleic acid.
3.3 PPAR Receptor Activation
Fatty acids tend to bind all three PPAR isoforms (α, β/δ, and γ) regardless of whether they are mono-unsaturated, polyunsaturated, C20 or C22 — the receptors are promiscuous in their choice of ligand. PPARs detect the dietary status of the body; if there is too much fat, PPAR is activated to increase fat burning, reduce appetite, and lower glucose levels. PPAR is therefore an attractive drug target, and modulation of PPAR activity is how fibrates and glitazone drugs affect metabolic risk factors. Studies using synthetic LCMUFAs show that both gondoic acid and cetoleic acid increase PPAR transcriptional activity to a similar level. In limited doses, erucic acid and gondoic acid have been reported to have a neuroprotective effect through action on peroxisome proliferator-activated receptors, and monounsaturated fatty acids generally are able to influence these receptors.
3.4 Lipid Metabolism Modulation
Studies on fish oil containing predominantly cetoleic acid but also gadoleic acid showed that these oils reduced atherosclerotic plaques, reduced LDL-cholesterol, and improved glucose metabolism. The mechanisms suggested by research on related MUFAs include modulation of hepatic cholesterol synthesis. Researchers suggest this fish-oil–associated fatty acid may improve lipid metabolism, reduce hepatic cholesterol synthesis, and potentially lower coronary heart disease risk.
A recent rat study found that "CETO3 herring oil administration to rats reduced risk factors for cardiometabolic syndrome by lowering plasma lipids, including TG [triglyceride] and LDL [cholesterol] and total FAs [fatty acids], possibly mediated by peroxisomal and mitochondrial FA oxidation."
3.5 Anti-Inflammatory Mechanisms
Other health benefits of MUFAs reported include hypolipidemic and anti-inflammatory effects. The anti-inflammatory effect in skin may result from the actions of LCMUFAs or from omega-3 lipids present in the oil, or from the increased conversion of ALA to EPA/DHA. The incorporation of cetoleic acid and related LCMUFAs into immune cell membranes is thought to affect signaling pathways relevant to inflammation, consistent with the broader effects observed with fatty acids on cellular membranes.
4. Scientific Evidence by Area of Use
4.1 Cardiovascular Health and Lipid Modification
Animal/Preclinical Evidence
Studies on mice demonstrate that fish oils rich in cetoleic acid reduce systemic inflammation and degree of atherosclerosis, while others have identified a link between intake and reduced risk of metabolic syndrome and obesity-related metabolic dysfunction.
One study pinpointed omega-11 (cetoleic acid)'s preventive effect on atherosclerosis in ApoE −/− mice, genetically exposed to atherosclerosis, fed a Western-style diet with the addition of (A) 3% butter, (B) 3% LC-MUFA C20:1, or (C) 3% cetoleic acid C22:1 n-11. The biomarkers of inflammation supported the evidence of the reduction, beside the reduction of lesions in the aorta by the LC-MUFA and especially cetoleic acid.
A systematic review and meta-analysis published in the British Journal of Nutrition specifically examined the cholesterol-lowering effect of cetoleic acid-rich oils in rodent models. Twelve articles were included in the systematic review and meta-analysis, with data from 288 rodents. Consumption of CA-rich fish oils and concentrates resulted in a significantly lower circulating total cholesterol (TC) concentration relative to comparator groups (mean difference −0.65 mmol/l, 95% CI (−0.93, −0.37), P < 0.00001), with high statistical heterogeneity (I² = 87%). The risk of bias is unclear since few of the entries in the SYRCLE's tool were addressed. The authors concluded that intake of CA-rich fish oils and concentrates prevents high cholesterol concentration in rodents and should be further investigated as functional dietary ingredients or supplements to reduce the risk for developing CVD in humans.
A 2024 preclinical study in diabetic rats found that the Norway-based researchers published their findings in the British Journal of Nutrition and noted that cholesterol, insulin sensitivity, and glucose levels are measures where standard fish oil with EPA/DHA has shown little or no effects. "The two marine oils, that is, herring oil (containing cetoleic acid) and anchovy oil (virtually devoid of cetoleic acid), had remarkably different effects on the cholesterol metabolism in diabetic rats." Five weeks of supplementation with cetoleic acid-rich fish oil also led to significant improvements in insulin sensitivity and glucose levels.
Human Clinical Evidence
As of 2026, the first randomized controlled trial in humans demonstrating a lipid-lowering effect of cetoleic acid has been published. Epax's cetoleic acid (CA) omega-9/omega-11 supplement derived from herring oil shows cardiovascular health promise by reducing LDL cholesterol by 7% after eight weeks in overweight and obese adults in a University of Bergen randomized clinical trial published in The British Journal of Nutrition. In this trial, participants consumed 4 g of oil daily by taking two capsules before lunch and two after dinner. They were instructed to avoid fish, seafood, omega-3 supplements, and most dietary supplements during the study, while otherwise maintaining their normal diet and lifestyle. Both interventions had comparable levels of omega-3, enabling the researchers to distinguish the effects of cetoleic acid concentrate from those of omega-3.
An ongoing clinical trial (NCT06172335) at Oslo University Hospital is further investigating cetoleic acid's effects on atherosclerosis markers. The study, entitled "Effects of Cetoleic Acid on Atherosclerosis," targets high-risk patients with metabolic syndrome and began recruiting in January 2024, with an estimated completion date of 2027. The intervention arm involves 6 capsules of intervention oil with high content of cetoleic acid (1,780 mg/day, estimated 29.76%) every morning for 4 weeks, while the control arm uses 6 capsules of control oil with low content of cetoleic acid (35 mg/day, estimated 0.58%) for the same period.
Evidence strength: For cardiovascular endpoints, the evidence base currently consists of a robust body of animal data (including a published systematic review and meta-analysis), one recently published randomized human trial showing a 7% LDL reduction, and at least one additional registered clinical trial underway. The human evidence is preliminary and the studies are small; replication in larger, longer-duration trials is needed before firm conclusions can be drawn.
4.2 Enhancement of the Omega-3 Index
Two placebo-controlled, double-blind human intervention studies were performed to assess cetoleic acid-rich oil (CRO) on the omega-3 index (O3I). Both studies were performed as double-blinded, placebo-controlled, randomised nutritional trials. The CetoIndex study (N = 55) measured omega-3 index using a blood spot collection kit.
In the CetoIndex study, 55 people were randomly assigned to receive 2 g per day of the cetoleic-rich oil (EPAX Cetoleic 10), 2 g per day of an anchovy "18/12" fish oil, or placebo (corn oil) for two months. The results showed that the Omega-3 Index increased in the anchovy oil group by 1.67%, while a 1.54% increase was recorded in the cetoleic-rich oil (CRO) group. No significant increase was observed in the placebo group.
The results of this pilot study suggest that the use of a CRO increases the omega-3 index more than expected from the levels of EPA and DHA in the oil. A separate smaller study with CETO3 also reported that following completion of the intervention, the increase in Omega-3 Index was slightly higher in the CETO3 group (5.73 ± 1.38%; P < 0.00001) than the fish oil group (6.24 ± 1.35%; P < 0.0003). That study used 30 participants between the ages of 20 and 70 years randomized to take 2 × 1 gram capsules of either CETO3 (400 mg/day, 200 mg of DHA/EPA, n = 14) or fish oil (FOil; 600 mg/day, 300 mg DHA/EPA, n = 16) for 12 weeks.
Evidence strength: Evidence for omega-3 index elevation is supported by in vitro mechanistic data and two small human pilot trials. Both human studies are limited by their small sample sizes, short durations, and pilot/exploratory design. Results are consistent and biologically plausible, but require confirmation in larger trials.
4.3 Skin Health and Dermatological Applications
Cetoleic acid-rich oils have been studied in two small human trials for skin outcomes. In the skin study ("Optihud"), a trial on 24 women randomized to administer either Epax Cetoleic 10 or corn oil placebo to assess the effects on healthy skin showed significant reductions in redness in the intervention group, indicating anti-inflammatory activity is relevant in skin.
Additional results from the skin health study, which employed a 4 g per day dose, showed that people consuming the cetoleic-rich oil had significantly less skin redness, which is connected to a lower inflammatory response to the facial cleansing process.
In conclusion, a fish oil rich in LCMUFA, represented by EPAX Cetoleic 10, increased the omega-3 index and showed potentially beneficial effects in skin erythema. This suggests the oil has an anti-inflammatory effect in skin, a finding consistent with results in other organ systems.
The CRO may potentially have benefits on skin inflammation. Further research exploring cetoleic acid's utility for eczema has been planned based on these preliminary findings.
Evidence strength: The dermatological evidence is very preliminary. The skin study involved only 24 women, lacked long-term follow-up, and did not assess clinical skin conditions such as eczema or psoriasis. The results are suggestive of an anti-inflammatory effect on skin but cannot be generalized without larger, adequately powered trials.
4.4 Metabolic Syndrome, Glucose Metabolism, and Insulin Sensitivity
Fish oils rich in omega-11 (cetoleic acid) may significantly reduce cholesterol by 14%, according to a new study from the University of Bergen and Haukeland University Hospital in Norway. Ten weeks of supplementation with the cetoleic acid-rich fish oil also exerted anti-inflammatory activity and mitochondrial activity, according to findings published in Frontiers in Nutrition.
Five weeks of supplementation with cetoleic acid-rich fish oil also led to significant improvements in insulin sensitivity and glucose levels in a diabetic rat model. The Norway-based researchers noted that cholesterol, insulin sensitivity, and glucose levels are measures where standard fish oil with EPA/DHA has shown little or no effects.
Evidence strength: Glucose and insulin metabolism findings are currently based exclusively on preclinical (rodent) models. No published human trial has yet specifically examined cetoleic acid's effects on glycemia or insulin sensitivity as primary endpoints. These are promising areas identified in animal studies warranting human investigation.
4.5 Neuroprotective Effects
The potential neuroprotective role of cetoleic acid is among the most nascent areas of research. A 2026 review in Lipids in Health and Disease comprehensively addressed this topic. Recent experimental research suggests that these lipids may provide benefits related to cardiovascular, but also brain health. Research on cetoleic acid using cell lines suggests that this fatty acid may positively affect neurological health.
The health effects of LC-MUFAs such as cetoleic acid, while studied, are not understood well at a mechanistic level. Knowledge specifically on cetoleic acid's health effects and its underlying molecular responses are currently lacking. The authors of this review note that omega-3 fatty acids, and particularly DHA, are key components for the development and homeostasis of neurons, and scientific literature agrees that higher circulatory levels of omega-3 fatty acids in patients are related to a better outcome of disease. Since cetoleic acid elevates endogenous EPA and DHA levels, it may indirectly contribute to neurological health through this mechanism.
Research has not progressed far regarding the direct neuroprotective effects of cetoleic acid, and mechanisms underlying such effects. As of late 2025, there exist a number of registered clinical trials examining health effects of cetoleic acid and marine oils containing high concentrations of cetoleic acid.
Evidence strength: Evidence for neuroprotective effects is extremely preliminary, resting on cell-line studies and theoretical extrapolation from related fatty acids. No human clinical trials have tested cetoleic acid specifically for neurological outcomes. This area is speculative and requires dedicated experimental and clinical research.
5. Body Systems and Health Areas of Association
- Cardiovascular system: Reduction of LDL cholesterol, total cholesterol, and triglycerides; attenuation of atherosclerotic plaque development in animal models; one confirmed human LDL reduction trial.
- Hepatic/metabolic system: Modulation of lipid metabolism in liver cells; peroxisomal and mitochondrial fatty acid oxidation; promotion of ALA-to-EPA/DHA conversion in hepatocytes.
- Endocrine/glycemic system: Improved insulin sensitivity and glucose metabolism in diabetic rat models; mechanism possibly related to PPAR activation.
- Integumentary system (skin): Reduction of facial skin erythema in two small human trials; possible anti-inflammatory action in skin consistent with subcutaneous fat distribution of LCMUFAs.
- Nervous system: Theoretical and cell-line-based data suggesting possible neuroprotective relevance; indirect benefit via increased DHA synthesis.
- Immune/inflammatory system: Modulation of cytokine levels in animal models of atherosclerosis; incorporation into immune cell membranes affecting inflammatory signaling.
6. Dosage Forms and Reported Dosages
Cetoleic acid is currently studied and commercially available as a component of standardized herring oil concentrates rather than as a pure isolated compound. The following dosages appear in published or registered studies:
- In the CetoIndex human study, 55 people were randomly assigned to receive 2 g per day of the cetoleic-rich oil (EPAX Cetoleic 10) for two months.
- The Optihud skin health study employed a 4 g per day dose of cetoleic-rich oil.
- In the University of Bergen LDL-cholesterol human RCT, participants consumed 4 g of oil daily by taking two capsules before lunch and two after dinner for eight weeks.
- The CETO3 omega-3 index study used 2 × 1 gram capsules of CETO3 (totaling 400 mg/day of cetoleic acid-containing oil, with 200 mg of DHA/EPA) for 12 weeks.
- In the registered Oslo University Hospital atherosclerosis clinical trial (NCT06172335), the intervention arm uses 6 capsules per day of oil providing cetoleic acid at an estimated 1,780 mg/day (approximately 29.76% of the oil) every morning for 4 weeks.
- In the ApoE −/− mouse atherosclerosis study, dietary supplementation was at 3% cetoleic acid C22:1 n-11 of diet composition.
No universally established or regulatory-approved human dosage for cetoleic acid as a dietary supplement currently exists. All dosages cited above are from research settings and do not constitute established therapeutic recommendations.
7. Safety Considerations and Interactions
7.1 Relationship to Erucic Acid and Established Toxicology
Cetoleic acid is described as toxic; its toxic effects are similar to those of erucic acid. This assertion requires contextual understanding. Erucic acid (22:1 n-9) is the positional isomer of cetoleic acid that has been extensively toxicologically evaluated by regulatory authorities. The heart is the principal target organ for toxic effects of erucic acid after exposure. Myocardial lipidosis was identified as the critical effect for chronic exposure.
Myocardial lipidosis has never been documented in humans, but in both experimental and production animals, such as rats, pigs, and chicken. The cause appears to be poor mitochondrial beta-oxidation of this fatty acid in the heart, resulting in an accumulation of erucic acid in neutral lipid droplets. There is primarily an increase in triacylglycerol, while the levels of phospholipids and cholesterol remain relatively constant.
The European Food Safety Authority (EFSA) published a risk assessment of erucic acid in feed and food in 2016, establishing a Tolerable Daily Intake (TDI) for humans of 7 mg/kg body weight per day based on the occurrence of cardiac lipidosis in experimental animals. This TDI applies formally to erucic acid (22:1 n-9), not cetoleic acid (22:1 n-11); however, given their structural similarity, regulatory caution is warranted.
7.2 Distinction Between Cetoleic Acid and Erucic Acid in Regulatory Context
EFSA's erucic acid assessment explicitly noted the co-occurrence of cetoleic acid in fish and seafood. Besides the occurrence in oil seeds, erucic acid also occurs naturally in fish and seafood. These food groups mainly contain cetoleic acid (22:1 n-11), which is usually accompanied by minor proportions of erucic acid. The EFSA report largely excluded the contribution of erucic acid from seafood, due to this fatty acid often not being reported separately in seafood.
The EFSA TDI is specifically calculated for erucic acid, and regulatory databases have historically not always distinguished clearly between C22:1 isomers. The EFSA report noted: "These food groups mainly contain cetoleic acid (22:1n-11), which is usually accompanied by minor proportions of erucic acid." The separate safety profile of cetoleic acid in humans has not been fully characterized in a dedicated long-term toxicological study.
7.3 Fish-Sourced Product Considerations
Cetoleic acid-rich oils derived from North Atlantic herring are subject to the standard quality controls relevant to fish oil supplements, including potential for oxidation and the presence of environmental contaminants. CETO3 is produced from Norwegian herring, which is "well regulated by the Norwegian authorities and is caught under Norwegian licenses in the North Atlantic." To ensure sustainability, all fish supplied to the plant are controlled for age, measured, weighed, and reported to the Norwegian Fishermen's Sales Organization for Pelagic Fish.
7.4 State of Knowledge and Research Gaps
The health effects of LC-MUFAs such as cetoleic acid, while studied, are not understood well at a mechanistic level. Knowledge specifically on cetoleic acid's health effects and its underlying molecular responses are currently lacking. The currently available human trials are uniformly small in size and short in duration, and no long-term safety data specific to isolated or concentrated cetoleic acid supplementation in humans has been published. Cetoleic acid-rich fish oils and concentrates should be further investigated as functional dietary ingredients or supplements to reduce the risk for developing CVD in humans — an acknowledgment from the research community that the evidence base is still in its formative stages.
References
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