Fish Oil Vs. Omega-3: Which Is the Better Supplement Option?

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Dr. Venus Ramos, M.D. Zveřejněno dne 15. ledna 2025

You’ve probably heard that omega-3s are great for your health. They play an important role in the makeup of cell membranes throughout the body and support proper cell communication.

Eating fish is an excellent way to get omega-3s into your system. Sometimes, however, it can be hard to include enough fish in your diet to reach your health goals. Taking a supplement can be a good way to ensure you are meeting your body’s needs.

But is it better to take a fish oil or omega-3 supplement? Let’s take a deep dive into the subject and explore the differences between the two, the benefits of each, and what to look for in a high-quality supplement so you can make the right choice.

The Difference Between Fish Oil and Omega-3

Fish oil is an oil produced from the tissues of fish. Omega-3s are fatty acids—specifically, polyunsaturated fatty acids.

Polyunsaturated is a scientific term to describe fatty acids with more than one carbon-to-carbon double bond. Monounsaturated fatty acids, like those found in avocados and olive oil, have only one such double bond. Saturated fatty acids, like those found in butter and coconut oil, have no such double bonds.

Omega-3s come in many different varieties, but there are three types you’ll see most frequently in scientific research—alpha-linolenic acid (ALA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA).

ALA comes from plant sources, like flaxseed, walnuts, and chia seeds. ALA is an essential fatty acid because the body cannot make it. So, it is a fatty acid that you must consume.

EPA and DHA are considered nonessential because the body can synthesize them. Humans have the enzymes to partly convert ALA to EPA and to some extent DHA. However, this conversion rate is low.^1,2,3

To achieve optimal levels of EPA and DHA, it’s best to get them from the foods you eat or through a supplement. Fish oil contains both EPA and DHA, making it a useful option for this need.

Sources of Omega-3s and Their Benefits

Fish Oil

Fish oil often comes as a byproduct of the animal feed industry. Herring, sardines, anchovies, mackerel, and menhaden are among the common fish used for this purpose. Their flesh is ground into fishmeal while the oil is used in fish feed, added to pet food, or refined for human supplementation.

Fish Liver Oil

Fish liver oil supplements, such as cod liver oil, contain EPA and DHA in relatively lower concentrations compared to fish oils. However, thanks to their origin in the liver, they are rich in vitamin A and vitamin D. These fat-soluble vitamins are not commonly present in fish oil supplements.

As a bonus, vitamin A is an antioxidant that can guard the omega-3 fatty acids against oxidation. When EPA and DHA oils oxidize, they become rancid, and you may notice a fishy or rotten taste or smell.

Algal Oil

Algal oil offers a source of DHA and EPA that is plant-based. In fact, the DHA and EPA found in fish come from the algae that small fish eat. These omega-3s get transferred up the food chain as larger fish eat the smaller fish. Because algal oil is at the beginning of this food chain, there is less concern about contaminants like mercury, which is a consideration when you consume fish products.

Krill Oil

Krill oil is extracted from Antarctic krill (Euphausia superba). This small shrimp-like animal gets its EPA and DHA content from the algae that it eats. Krill oil also contains the antioxidant astaxanthin. Naturally occurring vitamins A, D, and E add to krill oil’s antioxidant power.

Flaxseed Oil

Flaxseed oil contains ALA. Commonly known as the plant-based omega-3, ALA can also be found in walnuts, soybeans, hemp seeds, canola oil, chia seeds, and, in low quantities, dark leafy green vegetables.

What Forms of Omega-3 Exist?

Omega-3s come in both natural and synthetic forms. The natural forms include triglycerides (TG), phospholipids (PL), and free fatty acids (FFA).

The omega-3s in fish and fish oils exist mainly in TG and FFA forms. Algal oil offers omega-3s, mostly as triglycerides. In krill, a significant amount of omega-3s occur as phospholipids. FFA tends to be avoided in commercial preparations because FFA is very prone to oxidation, so can easily become rancid.

Ethyl ester (EE) is a synthetic form of omega-3.⁴ When fish is processed to refine its oil for use in supplements, food chemists often choose to convert triglycerides into ethyl esters. This makes it easier to manipulate the concentration of DHA and EPA in the oil.

It’s possible, however, to transform an EE back into a TG. This process is called re-esterification and results in a form of omega-3 called re-esterified or reformed triglyceride (rTG).⁴

Some manufacturers choose to convert EE’s to rTG’s because some research suggests the body absorbs triglycerides better than ethyl esters.^5,6 But there is still a market for omega-3 in EE form because you can improve EE absorption simply by consuming fat-containing food with it.⁷

What Are Some Health Benefits of Omega-3?

Omega-3s are associated with many potential benefits, from improved heart health, to reduced inflammation, to a lower risk of depression.⁸ Here’s a deeper look into how you may benefit from consuming more omega-3 fatty acids.

May Help Combat Inflammation

People are most familiar with inflammation as an acute response—it’s how your body fights infection and stimulates the healing process.

After an injury, you may experience pain, warmth, redness, and swelling in the affected area of your body. This acute inflammation results from your immune system sending white blood cells to the injury site.

When inflammation lingers, its chemical signals persist, and the whole process gets prolonged. This is called chronic inflammation. With chronic inflammation, your immune system may mistakenly recognize healthy tissues as a threat and attack them with white blood cells.

Research has linked chronic inflammation to developing conditions like cancer, arthritis, obesity, and heart disease.⁹

May Help Lower Triglycerides

You’ll see your triglycerides level listed as one of the numbers on a standard cholesterol blood test. Triglycerides are a type of fat that circulates in your blood. When you eat more calories than your body immediately needs, it converts them into triglycerides.

While it’s important to have a normal level of triglycerides, high triglycerides can lead to hardening or thickening of your arteries. This increases your risk of stroke, heart attack, and heart disease.

A review of 41 well-designed studies showed that EPA and DHA given as marine oils reduced triglyceride levels.10 Evidence from randomized controlled trials suggests dietary ALA decreases triglycerides as well.

May Improve Depression Symptoms

A review of 26 well-designed studies concluded omega-3s may have an overall beneficial effect on symptoms of depression.¹¹ The omega-3 formulations that showed this benefit had at least 60% EPA content. The effective dose was at least 1g of EPA per day.

Depression is a serious condition. So, it is wise to consult a health care professional and not rely on supplementation alone to manage symptoms of depression.

What to Look for When Choosing an Omega-3 Supplement

Walk down the supplement aisle of your grocery store, and you may be confronted with an impressive—if not overwhelming—a variety of omega-3 supplements. Here are a few factors to consider when choosing one to get the most effective omega-3 for your needs.

EPA/DHA Content

Reading the label to determine what you are actually getting in a supplement is important. Note what type of omega-3 the supplement contains—EPA, DHA, and/or ALA— and look at the amount of each type. For example, a supplement may have 1000mg of fish oil in each capsule but only 400mg of EPA and 200mg of DHA.

To ensure the claims made on a product label are accurate, check for a Current Good Manufacturing Practices (CGMP) certification. The FDA enforces CGMP regulations, helping you feel assured that the supplement contains what the label states.

The amounts of EPA, DHA and other fatty acid content were analyzed in a study of 47 commercial fish, krill, and algal oil supplements. Only 25% of the tested supplements contained at least the amount of DHA stated on the label. For EPA, only 21% had at least the stated amount.¹²

Also, find out what form of Omega-3 is in the supplement. Is it TG, rTG, PL, FFA, or EE? While EE may not be absorbed as well as the others, you can improve the absorption by consuming a fat-containing meal with it.7 Some manufacturers include an absorption enhancer in their EE formulations, so there may be no need for such a meal.

Knowing these facts about the product will help you get the most out of your omega-3 supplement—you can’t benefit from it if your body doesn’t absorb it.

Purity

Ensure the supplement meets a certain standard of quality. Contamination is a potential concern for fish oil. Heavy metals, PCBs (polychlorinated biphenyls), and organochlorine pesticides should be kept at an absolute minimum, if not completely eliminated.

Confirm that the supplement has undergone third-party testing. Look for a seal or certification of independent organizations like NSF International, United States Pharmacopeia (USP), Therapeutic Goods Association (TGA), or International Fish Oil Standards (IFOS).

Freshness

As previously mentioned, omega-3s are prone to oxidation and can readily go rancid if not properly handled and stored. Once they spoil, omega-3s may smell foul, lose potency, or even become harmful if consumed.

Check the expiration date, smell the product, and look for any antioxidants in the supplement like vitamins A or E. Heat can speed the spoilage rate. Therefore, generally, it’s wise to store the product in a dry and cool place after opening.

Dosage and Duration

Various health organizations have released their own recommendations on the total omega-3 a person needs daily. The exact amounts differ among the organizations, but the range tends to be between at least 250mg to 500mg of combined EPA and DHA to meet the basic nutritional needs of the general population.^13,14,15

Factors like age, diet, genetics, lifestyle, body weight and health condition are important when considering the right dose. It is best to seek the advice of a health professional for guidance in this area, especially if you have a medical condition.

Safety

The side effects of omega-3 supplements, if any occur, are generally mild. Possible adverse reactions include headache, bad breath, unpleasant taste, foul-smelling sweat, and gastrointestinal discomfort.

There is conflicting evidence about whether omega-3s affect the risk of prostate cancer. Some studies have found an increased risk of prostate cancer among men with higher blood levels of omega-3 fatty acids.¹⁶ But other research shows that a diet rich in omega-3s can help lower the risk of prostate cancer.¹⁷

Since large doses of omega-3 supplements can make your blood less likely to clot, consult your healthcare provider before starting omega-3 supplements if you are on blood thinners or other anticoagulants.

Also, some omega-3 supplements may not be tolerated by individuals allergic to seafood. As with all supplements, it is a good idea to consult your healthcare provider before adding omega-3s to your daily regimen.

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