Best fish oil, omega-3s and marine oil supplements – [Definitive guide]


Introduction – Omega-3 Fish Oil

  Omega-3s have been in the headlines numerous times in recent years, with fish oil being one of the most discussed and debated supplements in the world. These headlines have touted the health benefits of omega-3s as well as the cautions related to fish oil information, purity, rancidity, and potency. To further complicate things for consumers, other fish oil supplements have arrived on the market with claims of superiority over fish oil, such as krill oil. This article aims to highlight the health benefits of omega-3 fatty acids and evaluate the food and best fish oil supplement sources; shedding light on confusing fish oil information and presenting the best sources of these essential fatty acids related to your health objective. The pros and cons of each oil source are presented. Extraction processes will be briefly discussed to provide insight into stability, purity, and potency of omega-3 supplements. In addition, a checklist is provided on how to select high-quality fish oil and marine oil supplements. A summary table and infographic are included at the end of the article which will enable you to select the best fish oil or other marine oil supplement in supporting your specific needs.  

Omega-3s Explained

  Fat comes in three forms: saturated, polyunsaturated and monounsaturated. Like omega-6, omega-3 is a polyunsaturated fatty acid (PUFA). Omega-3 fatty acids are deemed essential since they are needed to sustain health, yet the body does not produce them. In modern society, the ideal proportion of omega-3 and omega-6 has fallen out of balance – from close to 1:1 in hunter-gatherer era to the omega 6 dominated present at 1:20 (1). Having too much omega-6 in the body and too little omega-3 leads to many diseases including cardiovascular, autoimmune, inflammatory, neurological, among others (2). There are three (3) main types of omega-3 PUFAs important for human physiology:

  • EPA (Eicosapentaenoic Acid) typically found in fatty fish, seafood, roe and algae;
  • DHA (Docosahexaenoic Acid) mostly found in fatty fish, seafood, roe and algae;
  • ALA (Alpha-Linolenic Acid) typically found in fatty plant foods including, but not limited, hemp hearts, walnuts, chia seeds, and flax.

Omega-3 fatty acids are one of the most-researched nutritional compounds in the world (3). Their health benefits are primarily attributed to EPA and DHA. EPA and DHA provide cell membranes their structure that allows them to retain beneficial compounds but expel waste. They also act as chemical triggers in the body reducing inflammation, activating the release of beneficial hormone-like compounds, and aiding communication amongst nerve cells. DHA makes up the majority of the PUFAs in the brain and is crucial in fetal development (4). ALA is a form of omega-3 but is not efficiently converted to EPA and DHA in the body (5). Polymorphisms in the FADS2 gene can further reduce the efficiency of this conversion. Nutrition Genome analysis can determine if such polymorphisms are present in your genetic code and provide guidance on how to improve gene function. For the above reasons, ALA is not a recommended form to ingest through diet; EPA and DHA sources should be sought. EPA and DHA come in many natural and processed forms:

  • Free fatty acids;
  • Phospholipid;
  • Triglyceride (three free fatty acids bound to glycerol);
  • Reformed triglycerides (ethyl esters converted back into triglycerides);
  • Ethyl esters (free fatty acid with an ethanol attached to the carboxyl end).
  • Whole foods containing EPA and DHA are in free fatty acid, phospholipid and triglyceride form. Whole crude marine oils (unrefined; minimally processed; natural fatty acid profile) are primarily made up of triglycerides, but will contain some phospholipids and free fatty acids (6). To enhance concentrations and improve purity, processed and refined marine oils tend to be ethyl esters or reformed triglycerides.

The forms listed above are presented in the order of bioavailability, from best to worst. Absorption of EPA and DHA further increase when consumed with a meal containing fat (7) (8) (9). Phospholipids have been shown to better improve the metabolic profile in obese mice when compared to triglycerides. Furthermore, EPA and DHA have increased uptake in human tissues when in phospholipid form (10). With that said, the relative difference in uptake of EPA and DHA fatty acids by form, as measured by phospholipid concentrations in the body after ingestion, is not major. Therefore the concentrations of EPA and DHA in supplement products may be a more important determinant in ensuring adequate levels get into the body. Lastly, marine oils that naturally contain phospholipids tend to have lower concentrations of EPA and DHA relative to processed fish oils. EPA and DHA are primarily ingested by consuming:

  • Whole marine foods;
  • Whole crude fish oil;
  • Processed fish oil;
  • Fish roe oil;
  • Krill oil;
  • Shellfish / Mussel oil;
  • Fish liver oils; and
  • Algal oil.

Some mammalian oils do offer EPA and DHA, but supply of such foods is limited and supplements of such are scarce. From a nutritional standpoint, the best source of EPA and DHA is from fatty sustainable cold-water fish such as wild sockeye salmon, since whole food provides numerous other minerals, nutrients, proteins and cofactors such as taurine, selenium, vitamin B12 and calcitonin, to name a few. Notwithstanding, eating fish 2-3 times per week may not be practical for some or affordable, and fish consumption can come with risks of contamination or sustainability if products are not selected prudently. Furthermore, eating fish provides lower doses of EPA and DHA than most research administers. Therefore, supplementation along with a diet of quality fish or supplementation alone, may be an option. Supplementation may be necessary to ensure adequate EPA and DHA levels are maintained in the body. It should be noted that majority of the epidemiological studies conducted use EPA and DHA from fish oil in triglyceride form (11). The remainder of the article will focus on the most beneficial forms of omega-3 (EPA and DHA), and the various marine source supplement oils that contain these fatty acids.  

High-Quality Fish Oil: Processing, Purity and Quality Control

  All marine oils are processed to some extent. Processed fish oil being the most refined and processed, whole crude fish oil being the least, with the others somewhere between those on the processing spectrum. Processing and refinement will also vary by supplement. Consumers should request information on processing if the supplier does not automatically disclose such information on their web page or product label. Below is a summary of common processing steps that take place after the extraction of the crude marine oil:

  1. Deodorization:  An evaporator is used to remove free fatty acids and contaminants from the crude oil;
  2. Ethylation:  This process uses a dilute acid to create ethyl esters;
  3. Distillation:  Distillation removes shorter chain ethyl esters and saturated fatty acids with the use of heat and a vacuum.  Distillation can be continued to concentrate EPA & DHA content;
  4. Cold Filtration:  Low temperature is used to precipitate compounds out of the oil.  Once they are solid they can then be filtered for exclusion;
  5. Glycerolysis:  An enzyme, acid or base catalyst is used with glycerol to reform ethyl esters into triglycerides. This step is not completed if products are to be sold as ethyl esters;
  6. Molecular Distillation:  Like deodorization, this process removes remaining glycerol or fatty acids not utilized in the triglyceride reforming step;
  7. Clay Filtering:  A step to eliminate very small pollutants;
  8. Blending:  The subsequent oil is mixed with substances, like antioxidants, to improve stability and protect against oxidation.  Common additives include vitamin E, rosemary oil, oregano oil and astaxanthin.  Other marine oil may be blended in at this stage to modify the EPA/DHA concentrations or fatty acid profile (12) (13) (14).

Marine oil quality has been improving in recent years due to negative publicity catalyzing producers to improve products and by increased consumer demand and awareness. Nevertheless, consumers still need to understand two factors that affect purity: contamination and oxidation. Contamination includes heavy metal contamination (lead, mercury, PCBs, etc.) and pesticide residues. Oxidation refers to the oxidation (degradation) of fatty acids and oxidation of other non-fatty acid compounds in the oil. As mentioned above, most manufacturers add in a variety of antioxidants to raw and finished products to minimize oxidation. Manufacturers also use low temperature and low light conditions to reduce oxidation during processing. Moreover, some capsules may utilize nitrogen (inert; purges oxygen) to prevent oxidation in the final product and extend shelf-life. Oxidation is measured and presented in the following ways:

  • Peroxide value (POV or PV) – this metric measures oxidized fatty acids;
  • Anisidine test (p-anisidine) – measures secondary oxidized compounds;
  • TOTOX value – a calculated measure being the sum of two times the peroxide value added to the anisidine value (15) (16).

Many reputable organizations are in now in place to provide guidance, testing and quality control of marine oils. Consumers should seek verification from producers that their products are staying below established contamination thresholds and do not exceed standards for oxidation. A Certificate of Analysis (COA) should be requested. A COA is an analysis completed by an independent (third party) lab to measure the ingredients in a product and confirm whether it meets producer claims. The COA will list the composition of fatty acids, include levels of toxins / contaminates and should provide oxidation values. Regulations and agencies that set standards and guidelines for fish oils and marine oils are listed below:


What are the “other ingredients” in Fish Oil?

  In addition to displaying the marine oil ingredients, most marine oil supplement labels will have “other ingredients” listed, which are usually associated with the material that encases the oil, coatings and compounds added for stability, such as antioxidants. These should also be scrutinized for additives, fillers and compounds that may be detrimental to human health or may not be congruent with your beliefs or ideologies. More specifically, these other ingredients may have implications related to kosher, GMO status, gluten, vegan/vegetarian, allergens or glutamate sensitivity (e.g. carrageenan). Fish and other marine oils are typically delivered within capsules or soft gels. Since capsules mask the taste and odor of the product, it may be beneficial to open one on occasion to determine if any off flavors or smells are present. The capsules are frequently made from gelatin, and some manufacturers also use enteric coatings to keep the capsule from dissolving completely in the stomach and instead the contents are released in the small intestine. Enteric coatings may reduce the possibility of fishy repeat but there has been limited studies supporting the claim that absorption is actually increased via this delayed delivery method. Two potential concerns related enteric coatings with marine oil products is the potential to reduce absorption/bioavailability and the ingestion of synthetic compounds used in the coating. These issues will vary according to the specific product so do your homework before purchasing.  

How to Choose the Best Quality Fish Oil to Take


  1. Define your health objective first (e.g. Inflammation, brain health etc.) and select product accordingly (Table 1 and the infographic )
  2. Choose wild (if possible)
  3. Lower on the food chain the better
  4. Choose sustainable sources – MSC certification; Friends of the Sea
  5. Look for quality control verification e.g. GMP, FHL guide, US/EUP compliance
  6. Request a COA
  7. Identify or request further purity and potency verification (3rd party testing) e.g.  NSF certification, IFOS certification, isura certification
  8. Study label details; the label should quantify all compounds in product (not just “Total Fat”), including antioxidants and Table 1 and the infographic 
  9. Identify other non-fatty acid (other) ingredients in the product including the capsule to ensure purity and that there are no conflicts with your health objectives or ideologies
  10. Choose highest quality, lowest cost product; quality should be sought over cost, if possible; if cost is high, it may be more beneficial to reduce dosage to make affordable versus consuming a greater quantity of lesser quality fish oil
  11. Generally speaking, processed fish oil will offer the lowest cost supplement source of EPA/DHA

The Best Fish Oil Supplements on the Market

Top Fish Oil: Whole crude fish oil

  An example of the best fish oil supplement to take is Wild Alaskan Salmon Oil. This oil is comprised primarily of triglycerides, with small amounts of phospholipids and free fatty acids. Most whole crude fish oils come from cod, herring or salmon and typically contain around 30% EPA and DHA by weight. These oils tend to be minimally processed and extracted through pressure with filtering. Salmon oil contains a natural antioxidant called astaxanthin, which aids with stability. Astaxanthin is a powerful antioxidant carotenoid that governs free radical activity, and has been shown to support joint, DNA, brain, cardiovascular, immune, and mitochondrial health. It also crosses the blood-retina barrier offering potential in the prevention of glaucoma and macular degeneration (17). Minimal refinement of these fish oils aids with stability since the oil is left in its natural state/composition. Purity may be improved if mostly fish heads are used since some contaminants do not cross the blood-brain barrier (18). Pros:

  • whole spectrum fish oil;
  • natural fatty acid oil composition;
  • contains naturally occurring vitamin A, D and astaxanthin;
  • minimally processed;
  • good bioavailability due to mixed forms of EPA and DHA;
  • good stability.


  • low concentration of EPA and DHA relative to total fat content;
  • low quantity of phospholipids;
  • qualities differ by fish species used;
  • sustainability concerns depending on the species;
  • natural astaxanthin levels (if present) may be too low to offer health benefits identified in human studies.

Best Whole Crude Fish Oil Supplement

1. North American Herb and Spice PolarPower Wild Salmon Oil 2. Vital Choice Wild Salmon Oil 3. Natural Factors Wild Salmon Oil 4. New Chapter Wholemega  

Top Fish Oil: Fish Roe Oil

An example of the best fish oil to take from roe is Herring Roe Oil.  Roe oils are comprised of 38%-75% phospholipids, with the rest being primarily in triglyceride form (10).  Roe oil from some species will contain naturally occurring astaxanthin.  Roe oil contains naturally occurring choline.  Choline is an essential nutrient for humans; necessary for proper liver function, neurotransmitter activity, and memory and brain development (10).  The inclusion of phospholipids and astaxanthin aid in stability. Pros:

  • contains high levels of phospholipids;
  • contains naturally occurring astaxanthin (fish species dependent);
  • contains naturally occurring choline;
  • good percentage of EPA and DHA present;
  • excellent efficacy due to phospholipid content;
  • good stability;
  • high abundance and often a waste product of commercial fishing.


  • roe oil tends to be refined then mixed with triglyceride fish oil;
  • lacks naturally occurring vitamins;
  • lack of research and human trials;
  • astaxanthin levels may be too low to offer health benefits identified in human studies.


Best Roe Oil Supplement

1. Whole Earth and Sea Herring Roe Oil  

Top Fish Oil: Processed fish oil

Fish oils are highly refined and processed, which is conducive to higher concentrations of EPA and DHA. High DHA fish oil and high EPA fish oil products are produced through this method and are touted as the best omega-3 supplements on the market. Processed fish oil supplement may contain upwards of 70% EPA and DHA by weight.  Supplements are typically made from sardine, anchovy and/or mackerel.   Most processed fish oils are primarily in ethyl ester or reformed triglyceride form but some, such as salmon, may have a greater occurrence of phospholipids; upwards of one-third (1/3) of the EPA and DHA being bound to phospholipids (10). High levels of processing allow for exceptional purity but reduces stability. How much fish oil should you take per day? With processed fish oil, the standard dose is 2-3 grams daily, but this amount varies based on the individual and goals. Pros:

  • majority of research on humans is conducted with this source of EPA and DHA, including a meta-analysis for abdominal weight loss when combined with lifestyle modification;
  • EPA:DHA ratio can be modified with processing to target different health benefits;
  • provides the most concentrated source of EPA and DHA;
  • these are the purest fish oils due to processes such as molecular distillation.


  • lack of natural cofactors;
  • reduced stability due to processing;
  • more prone to oxidation;
  • no naturally occurring vitamins in final product;
  • possible reduced bioavailability due to fatty acid form(s);
  • purity and stability varies by product;
  • sustainability may be an issue depending on the fish species used.


Best Processed Fish Oil Supplement

1. Nordic Naturals Ultimate Omega  

Top Fish Oil: Krill Oil

Krill oil is most commonly extracted from Antarctic krill (Euphausia superba).  Krill is a shrimp like creature that is present low on the food chain and in great abundance. Krill extraction involves a multi-step process using solvent extraction and multiple filtration stages, differing from fish oil manufacturing.  40% of the oil extracted from krill is usually in the phospholipid form; mostly present as phosphatidylcholine.  Krill naturally contains choline and astaxanthin.  Some studies have shown EPA and DHA delivered in krill oil to be more effective in humans, mostly attributed to the phospholipid form (10).  Overall, EPA and DHA levels in krill oil are low as a percentage of total fatty acids, and majority of fatty acids are still in triglyceride form.   Pros:

  • highly bioavailable;
  • good purity due to low contamination of krill;
  • contains natural astaxanthin, choline and phospholipids;
  • excellent stability;
  • sustainable source of EPA and DHA.


  • lack of research;
  • low EPA and DHA concentrations;
  • higher cost;
  • minimal naturally occurring vitamins;
  • astaxanthin levels may be too low to offer health benefits shown in human studies.


Best Krill Oil Supplement

1. Dr. Mercola Krill Oil 2. Neptune Krill Oil 3. Seeking Health Optimal Krill Oil 4. NutriStart Krill Oil  

Top Fish Oil: Cod Liver Oil

Cod liver oil typically refers to the extraction of liver oil from Atlantic cod (Gadus Morhua), although other species are used.  This species is considered the preferred cod liver oil based on learning from traditional cultures and a common fish oil used for kids, bodybuilders and those trying to increase immunity. Cod liver oil is a by-product of the cod meat market.  Cod liver oil typically provides a blend of fatty acids similar to a whole crude fish oil (i.e. around 30% EPA and DHA by weight with most fatty acids in triglyceride form) (19).  Cod liver oil contains high levels of vitamin A, moderate amounts of vitamin D and some vitamin E (20).  Other natural co-factors may be present if the oil is minimally processed such as in some fermented and extra virgin products. Pros:

  • whole spectrum fish liver oil;
  • contains naturally occurring vitamin A, D and E;
  • minimally processed;
  • good bioavailability with majority of EPA and DHA being triglycerides;
  • good stability;
  • sustainable as a market by-product.


  • lower concentration of EPA and DHA relative to total fat;
  • lacks phospholipids;
  • lacks choline and astaxanthin;
  • qualities differ by fish species used;
  • purity may suffer with lack of processing to eliminate natural contamination;
  • more research needed in humans;
  • fermentation methods have not been scientifically validated;
  • Vitamin A toxicity may be an issue at high doses


Best Cod Liver Oil Supplement

1. Rosita Cod Liver Oil 2. Virgin Cod Liver Oil by Nutrapro International  

Ratfish Liver Oil

Ratfish liver oil is an oil extracted from the liver of Ratfish (Chimaera Monstrosa).  It is very similar in composition to cod liver oil but offers lower levels of Vitamin A, D and E (19) (21).  Ratfish is a bottom dwelling fish and may contain higher levels of contaminants relative to cod liver oil.  Most products use some sort of processing to remove contaminants.  Ratfish oil may contain Squalene, a compound with impressive antioxidant and skin protection properties, a promising detoxification role and intriguing anti-cancer properties (22).  Ratfish liver oil contains a significant amount of alkylglycerols.  Alkylglycerols have been shown to boost the immune system, reduce inflammation, act as a blood antioxidant and may provide anti-cancer properties (23).  Minimal information is available on this oil and some claims must be deduced from studies on shark liver oil, which offers similar compounds. Pros:

  • whole spectrum fish oil;
  • contains naturally occurring vitamin A, D and E;
  • minimally processed; good bioavailability with majority of EPA and DHA being triglycerides;
  • good stability;
  • sustainable since a non-market fish species / bottom dweller;
  • may contain squalene;
  • contains alkylglycerols.


  • major lack of research;
  • only product test data is available to rely on for analysis of contamination, composition, and purity;
  • lower concentrations of EPA and DHA;
  • lacks other beneficial compounds found in other marine oils;
  • purity may suffer with lack of processing to eliminate natural contamination.


Best Ratfish Liver Oil Supplement

1. Rosita Ratfish Oil   

Skate Liver Oil

Skate liver oil is an oil extracted from the liver of the Skate (Beringraja rhina), a cartilaginous fish like the shark.  It is very similar in composition to cod liver oil but offers lower levels of Vitamin A and D but greater levels of Vitamin E (19).  Most products use some sort of processing to remove contaminants.  Skate oil contains Squalene (24) (22) (25).   Skate liver oil also contains alkylglycerols and glycosaminoglycans (26) (27).  Glycosaminoglycans have shown positive therapeutic effects related to blood clotting, formation of new blood vessels, cancer, inflammation, and microbial infections  (28).  Minimal information is available on this liver oil.  Research on shark liver oil may offer some insight into the potential benefits of this oil since shark liver oil contains similar compounds and they are a related species. Pros:

  • whole spectrum fish oil;
  • contains naturally occurring vitamin A, D and E;
  • minimally processed
  • good bioavailability with majority of EPA and DHA being triglycerides;
  • good stability;
  • contains squalene;
  • contains alkylglycerols;
  • contains glycosaminoglycans.


  • Sustainability may be a concern;
  • major lack of research;
  • squalene and other beneficial compounds vary by skate species;
  • skate species not always disclosed;
  • minimal test data available to rely on for analysis of contamination, composition and purity;
  • low concentrations of EPA and DHA;
  • lacks other beneficial compounds found in other marine oils;
  • purity may suffer with lack of processing to eliminate natural contamination;
  • lack of products on the market;
  • fermentation methods have not been scientifically proven for quality, purity and potency.


Best Skate Liver Oil Supplement

1. Green Pastures Skate Liver Oil  

Green Lipped Mussel Oil

Shellfish are not a common source for omega-3 fatty acid supplements.  Nonetheless, some products are presently on the market consisting of fatty acids derived from Green-Lipped Mussels (Perna canaliculus), most often caught off the shores of New Zealand. Green Lipped Mussel Oil (GLMO) provides a profile of various fatty acids.  EPA and DHA form part of this profile; typically in a 2:1 or 3:1 ratio. Inadequate research has been done using Green Lipped Mussel oil as the ingested oil to attain EPA and DHA outcomes.  Most research to date has studied its effects on arthritis and inflammation.  GLMO is rich source of rare fatty acids not found in most marine oil extracts: eicosatetraenoic acid (ETA) and its precursor stearidonic acid (SDA).  ETA and SDA provide unique benefits for osteoarthritis and rheumatoid arthritis; they are shown to be more effective at reducing inflammation at significantly lower doses than EPA and DHA. GLMO also contains glycosaminoglycans (29) (30) (31) (32) (33) (34). Pros:

  • sustainable source;
  • contains varied profile of fatty acids;
  • contains rare fatty acids ETA and SDA;
  • contains glycosaminoglycans;
  • good bioavailability;
  • good stability.


  • lack of research on this marine oil;
  • lack of research on ETA and SDA;
  • very few products on the market;
  • minimal beneficial co-factors, vitamins and antioxidants compared to other marine oils;
  • low EPA and DHA content.


Best Green Lipped Mussel Oil Supplement

1. Orthomolecular Green Lipped Mussel Oil  

Algal Oil

Various species of algae are commercial sources for omega-3 fatty acids, with most being Schizochytrium oil (Schizochytrium spp.) Many of these products are almost completely DHA. Algal oil is primarily in triglyceride form and EPA and DHA can be very concentrated like processed fish oil.  Algal has an exceptionally low risk of contamination (low on the food chain), thus so does its oil.  It is a sustainable source of EPA and DHA since algae are in abundance.  Algal oil also provides an option for vegetarians and vegans.  Overall, it is very similar in qualities to processed fish oil but may offer better stability (less processing required), a more sustainable EPA and DHA option, with less risk of contamination. Pros:

  • suitable for vegans;
  • excellent purity;
  • good stability;
  • high levels of EPA and DHA;
  • EPA:DHA ratio can be modified with processing;
  • may contain astaxanthin;
  • sustainable.


  • limited research using algal oil as the delivery agent for EPA and DHA in humans;
  • less products on the market compared to fish oil;
  • lack of natural cofactors;
  • potential reduced stability due to processing in highly concentrated EPA and DHA products;
  • no naturally occurring vitamins in final product;


Best Algae Oil Supplement

1. Nordic Naturals Algae Oil 2. Whole Earth and Sea Algae  

Summary: Choosing the Right Fish Oil 

Here is a summary of the information and analysis in this article in a simplified, visual, quick reference to aid in supplement selection. Choosing the Right Fish Oil Infographic: Choosing the Right Fish Oil



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*Alex is no longer able to answer comments due to very limited time outside of Nutrition Genome. If you are interested in nutrigenomic testing, please check out