Understanding How Much Fish Oil and Flaxseed Oil to Take

November 2, 2025 •

3 min read

According to the National Institutes of Health, most adults in the US consume adequate alpha-linolenic acid (ALA), but fall short on consuming enough eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This makes understanding how much fish oil and flaxseed oil to take an important consideration for optimizing omega-3 intake.

Quick Summary

This article details the differences between fish oil (EPA and DHA) and flaxseed oil (ALA), contrasting their bioavailability and discussing specific health applications like heart health, inflammation, and digestive support. Guidance on choosing the right supplement based on individual needs and dietary preferences is also provided.

Key Points

Differentiate omega-3s: Fish oil supplies readily usable EPA and DHA, while flaxseed oil offers ALA, which converts inefficiently to the active forms in the human body.
Fish oil content: Fish oil supplements typically contain varying amounts of combined EPA and DHA; checking the label is important.
Flaxseed oil content: Flaxseed oil is a source of ALA; one tablespoon provides a significant amount of ALA, but conversion to EPA/DHA is limited.
Potential side effects: High intake of omega-3s can potentially cause effects like digestive upset and, at significant amounts, may affect blood clotting.
Dietary preferences: Flaxseed oil is a plant-based omega-3 source suitable for vegetarians and vegans, while fish oil is not.
Proper storage: Both oils are prone to oxidation, so storing them in a cool, dark, or refrigerated environment is necessary to maintain their quality.
Seek professional advice: Always speak with a healthcare provider before considering a new supplement, especially if you have pre-existing conditions or are on other medications.

Understanding Omega-3s: The Difference Between ALA, EPA, and DHA

Omega-3 fatty acids are a group of essential fats that are crucial for overall health, influencing everything from brain function to inflammation. The three main types are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

ALA is a plant-based omega-3 primarily found in seeds and nuts like flaxseed, chia seeds, and walnuts. While the body can convert ALA into EPA and DHA, this process is highly inefficient in humans, with conversion rates typically less than 15%.
EPA and DHA are the "active" forms of omega-3, predominantly found in marine sources like fatty fish (salmon, mackerel, sardines) and algae. The body can use these forms directly, making them more bioavailable than ALA.

General Considerations for Fish Oil (EPA and DHA)

For most healthy adults, optimizing their intake of combined EPA and DHA is beneficial for overall health. This can often be achieved through dietary sources like fatty fish or with the assistance of supplementation. The amount of EPA and DHA in fish oil supplements can vary, making it important to check product labels. For individuals with specific health concerns like heart disease, healthcare providers may offer personalized recommendations, sometimes involving higher amounts of EPA and DHA.

General Considerations for Flaxseed Oil (ALA)

Flaxseed oil is a significant source of ALA, contributing to the adequate intake levels for this omega-3 fatty acid. The adequate intake for ALA is based on factors such as gender. However, due to the limited conversion of ALA to the active EPA and DHA forms, relying solely on flaxseed oil for all omega-3 needs may not be sufficient for certain health objectives. Flaxseed oil also offers unique potential benefits, particularly for digestive health.

Choosing Between Fish Oil and Flaxseed Oil

Your choice depends largely on your dietary habits, health goals, and ethical considerations. Fish oil provides a direct, highly efficient source of the active omega-3s, EPA and DHA, which are crucial for cardiovascular, cognitive, and anti-inflammatory benefits. Flaxseed oil, as a plant-based alternative, is suitable for vegetarians or those with fish allergies and also offers unique benefits for digestive health.


Feature	Fish Oil	Flaxseed Oil
Primary Omega-3s	EPA and DHA	ALA
Conversion to Active Form	Not required; immediately bioavailable	Inefficient conversion to EPA and DHA in the body
Source	Fatty fish (e.g., salmon, mackerel)	Flaxseeds
Ideal For	Cardiovascular health, brain function, inflammation, eye health	Vegetarians, vegans, or those with fish allergies
Special Benefit	More direct anti-inflammatory and triglyceride-lowering effects	Gastrointestinal support (laxative/anti-diarrheal effects)
Potential Concern	Mercury levels (typically tested for in supplements), potential for rancidity	Poor conversion to active forms, potential for rancidity

Practical Supplementation Tips

When considering supplements, consistency and quality are key. For fish oil, looking for supplements that specify the amounts of EPA and DHA on the label is helpful, as these are important measures. For both oils, storing them in a cool, dark place or the refrigerator can help prevent oxidation and maintain freshness. Taking supplements with a meal that contains other fats may also aid absorption.

Final Thoughts

Ultimately, the best approach depends on individual needs. A person focused on maximizing active EPA and DHA levels for heart and brain health will likely prefer fish oil or an algae-based supplement. Conversely, someone who is vegetarian or vegan, or is primarily concerned with ALA's potential benefits and digestive health, will lean towards flaxseed oil. Consulting with a healthcare provider is always recommended to discuss which omega-3 source is best and to address any potential interactions or concerns, especially for specific health conditions or while taking other medications.

Conclusion

When considering omega-3 sources like fish oil and flaxseed oil, it is essential to understand their distinct compositions. Fish oil provides direct and potent EPA and DHA, making it a valuable option for cardiovascular and cognitive health. Flaxseed oil offers a plant-based source of ALA, which provides general health benefits but converts inefficiently to the active forms. By considering your specific health goals and dietary needs, you can work with a healthcare professional to make an informed decision on which omega-3 source is most suitable for you.

This content is for informational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider for any health concerns or before starting a new supplement regimen.

Frequently Asked Questions

Fish oil is generally considered more effective for maximizing EPA and DHA levels in the body, as it provides these active forms directly. Flaxseed oil contains ALA, which converts inefficiently into EPA and DHA, meaning its benefits for concerns like heart health and inflammation may be less direct compared to fish oil.

Yes, it is possible to take both supplements. However, it's important to consult a healthcare provider first, as taking high amounts of omega-3s from any source can potentially affect blood clotting. A combined approach can provide a broad spectrum of omega-3s, but a balanced diet might already supply sufficient ALA from plant sources.

Consuming very large amounts of omega-3s from supplements might lead to effects such as nausea, diarrhea, acid reflux, and a potential increase in the risk of bleeding. It is advisable to discuss appropriate intake levels with a healthcare professional.

Both fish and flaxseed oils are sensitive to light and heat, which can cause them to spoil. They should be stored in a cool, dark place, such as the refrigerator, to preserve their freshness and prevent them from becoming rancid. Checking the expiration date is also important.

While flaxseed oil is a suitable plant-based source of omega-3 (ALA) for vegetarians and vegans, it is not a direct replacement for fish oil when seeking high levels of EPA and DHA. Because the conversion of ALA to the active EPA and DHA is inefficient, vegetarians looking to boost EPA and DHA levels may consider algae-based supplements, which provide these forms directly.

Yes, some research suggests that flaxseed oil may be beneficial for gastrointestinal health. Its properties may help promote bowel regularity and stool consistency.

The most effective way to determine your omega-3 needs is to consult a healthcare provider. They can assess your diet, health status, and goals, and, if necessary, recommend appropriate testing. This personalized approach can help you understand which omega-3 sources and amounts might be most beneficial for you.