What is the best way to get DHA?: Your Guide to Optimal Sources

November 2, 2025 •

4 min read

DHA is a critical omega-3 fatty acid, making up a significant portion of the brain's gray matter and the eye's retina. Since the body’s conversion rate of plant-based omega-3 (ALA) to DHA is very low, understanding what is the best way to get DHA is essential for optimal health across all life stages.

Quick Summary

This guide examines the most effective methods for obtaining docosahexaenoic acid, an essential omega-3 fatty acid. It covers rich marine sources like fatty fish, sustainable plant-based options from algae, and the role of high-quality supplements for ensuring sufficient intake.

Key Points

Fatty Fish Are the Top Direct Source: Cold-water, oily fish like salmon, mackerel, and sardines contain the highest natural levels of preformed DHA and EPA.
Algal Oil is Best for Plant-Based Diets: For vegans and vegetarians, algal oil derived from microalgae is the only direct source of DHA and EPA, bypassing the body's inefficient conversion of ALA.
Supplements Provide Reliable Dosage: Fish oil, krill oil, and algal oil supplements offer a convenient way to ensure consistent DHA intake, especially for those with dietary restrictions or who eat limited seafood.
ALA from Seeds and Nuts Converts Poorly: Plant-based sources like flaxseed and walnuts contain ALA, but the human body's conversion to active DHA is very low and unreliable for meeting needs.
Consider Contaminants with Marine Sources: When consuming fish, choose smaller varieties like sardines to minimize potential exposure to mercury, which can accumulate in larger predatory fish.
DHA Is Crucial for Brain and Eye Health: Adequate DHA intake is essential for fetal development, cognitive function, vision, and reducing inflammation throughout life.

What Is DHA and Why Do We Need It?

Docosahexaenoic acid (DHA) is a polyunsaturated omega-3 fatty acid that is vital for health. It is a major structural component of the human brain, cerebral cortex, skin, and retina. Our bodies need DHA to function properly, particularly for cognitive development and function, visual health, and reducing inflammation. While the body can convert a plant-based omega-3, alpha-linolenic acid (ALA), into DHA, this conversion is very limited and often insufficient to meet daily needs. For this reason, consuming DHA directly from dietary sources or supplements is the most practical and efficient method.

Marine Sources: The Direct Route to DHA

For those who consume animal products, marine-based foods are the most potent and direct sources of DHA and its precursor, EPA. Both oily fish and shellfish accumulate these fatty acids from the microalgae they consume, concentrating them in their tissues.

Oily Fish Fatty, cold-water fish are at the top of the list for DHA content. Examples include:

Salmon: A 3.5-ounce serving of cooked, farmed salmon contains approximately 1.46 g of DHA.
Mackerel: Atlantic mackerel offers about 0.7 g of DHA per 3.5-ounce serving.
Sardines: Canned sardines are a concentrated source, providing around 0.51 g of DHA per 3.5-ounce serving.
Herring: An Atlantic herring fillet (5-ounce) contains about 1.58 g of DHA.
Tuna: The DHA content varies. Bluefin tuna has a high concentration, while canned light tuna is still a good source.

Shellfish Many shellfish also contain valuable amounts of DHA and EPA:

Oysters: These are unique as they contain all three major omega-3 types and provide about 0.5 g of DHA per 3.5-ounce serving.
Mussels: A 3-ounce serving of cooked blue mussels offers 0.43 g of DHA.
Crab and Shrimp: While containing smaller amounts than oily fish, they still contribute to overall intake.

Plant-Based Sources for Vegans and Vegetarians

For those on a vegan or vegetarian diet, relying on the body's conversion of ALA is not reliable for optimal DHA levels. The solution lies in supplements or fortified foods derived from the original source of marine omega-3s: algae.

Algal Oil: This oil is extracted directly from microalgae, such as Schizochytrium sp., and is the only direct plant-based source of DHA and EPA. Algal oil supplements are highly effective and sustainable, offering a clean, marine-free source of the fatty acid.
ALA-rich plant foods: While not direct sources of DHA, foods rich in ALA can contribute modestly. These include flaxseeds, chia seeds, hemp seeds, and walnuts. Vegan and vegetarian diets should prioritize these, along with algal oil supplementation.

DHA Supplements: A Convenient Option

For many, especially those who don't regularly consume marine life or have a difficult time meeting their needs through diet alone, supplements are a convenient and effective solution. Options include:

Fish Oil: The most common omega-3 supplement, fish oil, contains both EPA and DHA in varying concentrations. The bioavailability can depend on the form, with triglyceride forms often being better absorbed than ethyl ester forms.
Krill Oil: Derived from tiny crustaceans, krill oil provides DHA and EPA bound to phospholipids, which some research suggests may be more readily absorbed than triglycerides.
Algal Oil: As mentioned, this supplement is ideal for vegans and vegetarians, providing a direct source of DHA and EPA.

Supplements should be chosen from reputable manufacturers and ideally carry third-party seals for purity and potency. A healthcare provider can offer personalized guidance on the appropriate dosage.

Comparison of DHA Sources


Source	DHA Content	Bioavailability	Diet Suitability	Notes
Oily Fish (Salmon, Mackerel, Sardines)	High (EPA & DHA)	Excellent	Omnivore/Pescatarian	Highest natural concentration of DHA and EPA. Potential for mercury contamination in larger predatory fish.
Algal Oil (Supplements, Fortified Foods)	High (Direct DHA & EPA)	Excellent	Vegan/Vegetarian	Direct plant-based source. Sustainable and free from marine contaminants.
Plant-based ALA (Flaxseed, Walnuts, Chia)	None (ALA only)	Very Low Conversion to DHA	Vegan/Vegetarian	Body's conversion to DHA is inefficient. Useful for overall health but insufficient for DHA needs alone.
Fish Oil (Supplements)	Variable	Good to Excellent	Omnivore/Pescatarian	Common supplement form. Purity can vary between brands. Often provides both EPA and DHA.
Krill Oil (Supplements)	Lower than Fish Oil	Potentially Higher than Fish Oil	Omnivore/Pescatarian	DHA is bound to phospholipids. More sustainable than some fish sources.

Addressing Dietary Challenges and Risks

Certain populations face particular challenges in obtaining enough DHA. Pregnant and breastfeeding women, in particular, have increased needs to support fetal and infant brain development. In these cases, supplementation is often recommended, especially if seafood intake is limited due to concerns about mercury or other pollutants. Health guidelines often suggest opting for smaller, fatty fish like salmon and sardines to minimize exposure to contaminants. For those who follow strict plant-based diets, algal oil is the best way to ensure optimal DHA intake and avoid deficiency-related symptoms like dry skin, fatigue, and poor concentration.

Conclusion

In summary, the best way to get DHA is through a targeted approach that considers your dietary preferences and needs. For omnivores, incorporating 1-2 servings of fatty fish per week is an effective strategy. For vegans and vegetarians, opting for high-quality algal oil supplements is the most reliable method for obtaining direct DHA. Fortified foods can also contribute, but should not be the sole source. Since the human body's conversion of plant-based ALA to DHA is inefficient, a direct source is preferable for maximizing health benefits for the brain, eyes, and heart. Consulting a healthcare professional can help you determine the right strategy and dosage for your individual needs. For more information on DHA's functions, refer to the detailed analysis provided by IntechOpen.

Frequently Asked Questions

ALA (alpha-linolenic acid) is a plant-based omega-3 fatty acid found in nuts and seeds. The body can convert it into EPA and DHA, but at a very low rate. EPA and DHA are longer-chain omega-3s primarily found in marine sources like fish and algae.

Relying on ALA-rich plant foods like flaxseed and walnuts is insufficient because the body's conversion to DHA is limited. To meet optimal DHA requirements on a plant-based diet, supplements made from algal oil are recommended.

Larger, predatory fish can accumulate higher levels of contaminants like mercury. For this reason, official health guidelines often recommend choosing smaller fish species like salmon, sardines, and mackerel and limiting overall intake, especially for pregnant women.

Algal oil is a direct, vegetarian source of DHA and EPA, similar to fish oil. It is often more sustainable, avoids issues of ocean contaminants, and is suitable for vegans. Both provide bioavailable omega-3s.

Individuals who don't consume fish regularly, pregnant and breastfeeding women, and those on vegetarian or vegan diets should consider supplementation. It is also important for individuals who want to correct insufficient dietary intake.

Symptoms of omega-3 deficiency can include dry or flaky skin, fatigue, mood swings, poor concentration, and dry eyes. These signs often develop gradually over time.

DHA levels can be checked through a blood test called the Omega-3 Index, which measures the amount of EPA and DHA in your red blood cells. A doctor can order this test if necessary.