How to Choose the Best Fish Oil Supplement

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    In this article, we’ll explore what you need to know to choose the best omega-3 fish oil supplement for your needs.

    Omega-3 fatty acids are essential for your health. The human body can’t make them, so they have to be consumed from dietary sources. Many people do not regularly eat coldwater fatty fish, like salmon or mackerel, yet these are some of the best sources of healthy omega-3 fats. Fish oil supplements contain the same omega-3s and can help bridge the nutritional gap if you don’t eat much seafood. There are even vegan options if you’re allergic to fish or follow a plant-based diet.

    How to Choose the Best Omega-3 Supplement

    When you’re searching for the best omega-3 supplement, there are several factors to keep in mind.

    EPA & DHA Content

    When you are considering fish oil supplements, you want to know how much of each type of omega-3 you’re getting.

    There are three types of omega-3 fats: Eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). ALA, a type of omega-3 found in plant-origin foods, can be converted into EPA and DHA, but this process in the body is inefficient and is not considered a primary way to consume omega-3 essential fatty acids.

    Most fish oil supplements contain a mixture of EPA and DHA. Some may include more EPA, while others may provide more DHA per serving. Both types of fatty acids are essential, and the type of supplement you get depends on your health needs and your medical provider’s recommendation.

    Purity and Sustainability

    Purity and sustainability are terms that frequently come up with fish oil supplements.

    • Purity: Purity refers to the quality of the fish oil, and includes being free from contaminants or toxins such as dioxins, heavy metals, PCBs, and more. Since fish oil is concentrated, if it isn’t pure, it will also contain more concentrated levels of contaminants.
    • Sustainability: Sustainability describes how a manufacturer sources and processes fish oil. Sustainable sourcing refers to using fish that quickly repopulate, so as not to diminish a species for future generations. Sustainable processing refers to utilizing all parts of the fish, and not just the oil, to reduce waste.

    Most brands will describe their sustainability practices and policies on their websites or product pages. You can compare the standards of different brands to find one that aligns with your values and preferences.

    Capsules vs. Liquid Supplements

    Fish oil supplements come in many forms. Capsules and liquid supplements are common. Neither is better than the other from a nutritional standpoint The serving sizes for both types may differ, as well as the taste. If you struggle with the taste of fish, swallowing a capsule is one way to reduce the fishy aftertaste associated with liquid omega-3s.

    Regardless of the type of supplement you take, read the “other ingredients” label so that you know what else is in your product. These could include antioxidants, other preservatives, flavoring, colors, and more.

    Size of the Supplement

    Fish oil capsules tend to be larger compared to other capsule sizes, so if you struggle to swallow medium to large-sized capsules, a liquid or gummy supplement may be best for you. Not all fish oil capsules are the same size, and some brands may advertise having smaller capsules. If the size of the capsule is important to you, look for something that notes it has a small capsule, or find a liquid or gummy alternative.

    Taste and Smell

    Freshness is an important factor to consider when you choose a fish oil. Oils can go rancid if they do not have the proper antioxidants to stabilize them and keep them fresh. This is why many fish oils include vitamin E, which is an antioxidant, or lemon, which can act as a flavor to camouflage the taste, but also contains vitamin C, which is an antioxidant for freshness.

    Not all fish oil supplements include antioxidants or other ingredients to balance the taste or smell. A fish oil supplement may smell quite “fishy” and that does not mean it’s bad. Some people are intolerant of a fishy aftertaste, or “fish oil burps.” If this bothers you, you’ll want to find an omega-3 supplement that is enteric-coated, or one that includes lemon, lime, orange, or another flavor to help hide that fishy taste. Alternatively, you can get a vegan omega-3 supplement, which is derived from algal oil and contains no fish to leave behind that seafood aftertaste.

    Health Benefits of Omega-3s

    Omega-3 fats are necessary to support many aspects of healthy function throughout the body. Your body can’t synthesize them, so it depends on adequate supply from dietary intake. While there are many benefits, the following are some of the most well-known and science-backed ways that fish oil and omega-3s may support your wellness.

    Heart Support

    Food plans (like the Mediterranean Diet) that are rich in a variety of healthy nutrients, including seafood, are linked to heart health. While there are many elements of a healthy, omega-rich diet that support the heart, omega-3 fats have been shown to specifically support this vital organ. A meta-analysis of 38 trials, including data from more than 149,000 participants, found that omega-3 fatty acids were associated with heart health parameters. EPA in particular, compared to EPA with DHA, had a stronger link specifically for cardiovascular wellness.

    Omega-3s are also linked with healthy blood vessels, endothelial wellness, and markers of heart health.

    Brain Support

    EPA and DHA are both necessary for brain health. From fetal development through childhood, omega-3s are linked to brain health and function. While EPA has been noted for its importance in heart health, DHA has more of a standout role in supporting healthy brain and neuronal wellness. Cell membrane integrity and nerve communication depends on adequate access to DHA.

    While a significant amount of research is ongoing, healthy aging in the brain seems to be linked with adequate levels of DHA in the blood. Omega-3s may also be supportive of a healthy mood in addition to other lifestyle and therapeutic support.

    Eye Health Support

    DHA levels are concentrated in the retina and omega-3s are an important component of cellular membranes. Studies that have observed associations between intake of omega-3s and eye health have noted that consuming more essential fatty acids is linked with ocular wellness. However, observational studies cannot determine direct causation. Still, other larger studies have found the same association between omega-3 intake and eye health.

    Other research has looked at how omega-3s impact moisture, which is a necessary quality for healthy eyes. One study of 518 adults showed that 650 mg of EPA combined with 350 mg of DHA for 3 months produced better eye moisture than a placebo condition. Another trial of 105 adults found that over 12 weeks, 1,680 mg of EPA paired with 560 mg of DHA supported eye moisture better than a placebo. However, other studies have not been able to produce consistent results with omega-3s and eye moisture.

    While omega-3s are concentrated in the retina and support healthy cellular and tissue structure, more research is needed to firmly understand how omega-3s are linked to specific elements of eye health.

    The Different Types of Omega-3 Supplements

    There are four main categories of omega-3 supplements.

    Fish Oil

    Fish oil supplements are sourced from different types of fish, but may often include cod, mackerel, anchovies, herring, and salmon. The oils are concentrated to provide a high amount of omega-3s per serving size. Fish oil supplements usually involve some EPA and DHA, although the balance between them can vary dramatically.

    Krill Oil

    Krill oil supplements are derived from krill, a type of crustacean shellfish. Krill is also rich in EPA and DHA, like fish oil, but has a different fatty acid structure that may lead to a higher absorption rate (although more studies are needed). Krill oil also contains astaxanthin, an antioxidant that is naturally found in krill, and gives the supplement a reddish hue.

    Algal Oil

    Fish aren’t naturally high in EPA and DHA—it accumulates in them because they consume algae. As such, the concentrated oil that is derived from the same types of algae is also a rich source of EPA and DHA. In a small study that compared algal oil to salmon, both were able to raise blood levels of DHA. Another study found that supplementing with 600 mg of DHA from fish oil or algal oil produced the same percent increase of serum DHA levels. Because algae grows rapidly, it represents an even more sustainable source of omega-3s. It’s also free from the “fishy” taste that many find objectionable, making it a great omega-3 supplement for many needs or preferences.

    Flaxseed Oil

    Flaxseeds contain some omega-3s, although primarily in the form of ALA. While some of the ALA can be converted to EPA and DHA, it’s a far less efficient process than consuming EPA or DHA supplements like fish oil, krill oil, or algal oil. Flaxseed oil has its own benefits that extend beyond omega-3 content, but when it comes to a supplement that provides meaningful servings of EPA and DHA, flaxseed oil contains the least amount.


    Dosages of omega-3 supplements vary widely based on the manufacturer and the specific formulation. An average fish oil supplement may contain 1,000 mg of fish oil, where around 180 mg are EPA and 120 mg are DHA. However, it’s important to read the label on the specific product you have, since this can be much higher or lower.

    Work with your medical provider to determine the best intake for your health needs. At higher dosages, fish oil supplements have the potential to interact with certain medications or conditions.

    Side Effects

    Fish oil supplements are generally well tolerated. Some side effects can include:

    • Fishy aftertaste
    • Fishy burps
    • Indigestion
    • Diarrhea
    • Gas
    • Nausea

    Always consult your doctor if you have questions or concerns about how a supplement makes you feel.

    Frequently Asked Questions

    What form of omega-3 is best for absorption?

    Both EPA and DHA absorb well and are used by the body. ALA, a plant-based form of omega-3s, does not absorb as well. Omega-3s that come from fish or algal oil absorb better than from flaxseed.

    Can you take omega-3s oil every day?

    Omega-3 supplements can be taken every day unless your doctor says otherwise. If you have seafood, shellfish, or other allergy concerns, any health conditions, or take medications, work with your medical provider to determine if it’s best for you to take fish oil every day.

    When is the best time to take omega-3s?

    Omega-3s can be taken at any time of the day. Because they are fatty acids, they may absorb best when consumed with a meal that also contains some dietary fat.

    Can omega-3s cause constipation?

    While uncommon, constipation is a potential side effect of fish oil.

    Can omega-3s cause acne?

    Omega-3s can affect skin health in different ways. While some research has found that omega-3s improve skin symptoms, others have experienced a worsening of symptoms. Individual factors likely affect whether omega-3s lead to skin breakouts, but more research is needed.

    Can omega-3s cause headaches?

    Omega-3s are linked with improvements in headache-related symptoms. However, people who are sensitive to fish oil or the ingredients in omega-3 supplements should still be cautious.

    Will omega-3s break a fast?

    If you are fasting for medical reasons, only your doctor can advise you on what will or won’t break your fast. Generally speaking, if you consume a lower serving size of fish oil, it’s unlikely to break a fast. However, fish oil absorbs best when paired with a meal that contains some fat, so it is less likely to get the optimal benefit from omega-3 supplements if you take them on an empty stomach.

    The Bottom Line

    There are many types of omega-3 supplements to choose from, ranging from fish oil to vegan-friendly algal oil. The best omega-3 for you depends on your health needs, budget, food sensitivities, sustainability preferences, and more.

    While omega-3s don’t replace the need for a healthy, balanced nutrient intake, they can help to bridge the gap if you’re unable to eat seafood or need to support a higher intake of these essential fatty acids. Your healthcare provider can advise you on the best form of omega-3 as well as the optimal intake for your needs.

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    Dr. Pragati Gusmano, ND
    Formulator and Medical Researcher
    Dr. Gusmano is a licensed naturopathic physician. She received her doctoral degree from Bastyr University and has over a decade of experience in nutrition and the natural products industry. Her clinical interests include lifestyle medicine, optimizing nutrition at all stages of life, pediatrics, and mind-body medicine. In her free time, you’ll find her outside connecting with nature, spending time with her two children, and cooking plant-based meals.
    Mia McNew, MS
    Freelance Contributor
    Mia McNew is a nutrition science researcher with bachelor's and master's degrees in nutrition science and biochemistry. She holds additional certifications in clinical nutrition and formerly managed a private nutrition practice focusing on fertility and the management of chronic health and autoimmune disorders. She is currently pursuing a PhD in human nutrition with a research focus on disability, underserved populations, and inequities in popular nutrition therapy approaches. She has extensive experience as a fact-checker, researcher, and critical research analyst and is passionate about science and health communications that provide practical support.