What is DHA Typically Derived From? Explaining Its Primary Sources

December 15, 2025 •

3 min read

Approximately 93% of the omega-3 fatty acids in the human retina is DHA, highlighting its critical role in vision and brain function. While fatty fish are a well-known source, few people know that the journey of docosahexaenoic acid (DHA) begins at a more foundational level in the marine ecosystem.

Quick Summary

DHA is an essential omega-3 fatty acid derived primarily from marine microalgae, which is then consumed by fish. The most common dietary sources for humans are fatty, cold-water fish, though plant-based algal oil offers a direct vegan alternative for supplementation.

Key Points

Algae is the primary source: The journey of DHA begins with marine microalgae, which produce the fatty acid in their cells.
Fish get DHA from their diet: Fatty, cold-water fish do not produce DHA but accumulate it by feeding on microalgae and smaller fish in the marine food chain.
Fatty fish are rich sources: Species like salmon, mackerel, herring, and sardines are excellent dietary sources of DHA for humans.
Algal oil is a vegan alternative: Directly extracted from microalgae, algal oil provides a sustainable, contaminant-free source of DHA suitable for vegans.
ALA conversion is inefficient: The body can poorly convert the plant-based omega-3 ALA (found in flaxseed) into DHA, making direct intake important.
Supplements are widely available: Fish oil, krill oil, and algal oil are common supplemental sources used to ensure adequate DHA intake.
Bioavailability varies by form: The chemical structure of DHA in supplements can affect how well the body absorbs it, with triglycerides and phospholipids generally having high bioavailability.

The Foundational Source: Marine Microalgae

DHA's origin story starts with microscopic marine organisms known as microalgae. These single-celled plants produce DHA as a core part of their cellular structure. This process is fundamental to the marine food web, as these tiny organisms become the primary source of omega-3s for the larger animals that consume them. The microalgae species Schizochytrium sp. is one of the most prominent used for commercial production of algal oil, making it a sustainable, plant-based source for human consumption.

The Marine Food Chain

Fish, particularly cold-water species, don't produce their own DHA in significant amounts. Instead, they accumulate high concentrations of it by consuming microalgae or smaller organisms that have fed on the algae. This biological concentration effect is why fatty fish have historically been the richest source of DHA for humans.

Common Dietary and Supplemental Sources

For most people, the main sources of DHA come from the very organisms that have concentrated it through the food chain or from products directly derived from them.

Fatty Fish

Oily fish are the most well-known dietary source of preformed DHA for humans. Regular consumption is key to maintaining adequate levels because the human body cannot produce enough on its own.

Here are some of the best dietary sources of DHA:

Salmon: A fatty, cold-water fish rich in DHA and EPA.
Mackerel: Another excellent source, with high concentrations of omega-3s.
Herring: Often consumed pickled or canned, herring provides substantial amounts of DHA.
Sardines: These small fish are packed with omega-3s and are a low-mercury option.
Tuna: While a good source, consumption should be moderated due to potential mercury levels, especially for certain populations like pregnant women.

Algal Oil

For vegetarians, vegans, or those with seafood allergies, algal oil is a revolutionary and sustainable source of DHA. It is extracted directly from the microalgae, cutting out the middle-fish and providing a pure, contaminant-free, and plant-based option. This oil is increasingly found in fortified foods, infant formulas, and dedicated dietary supplements.

Other Sources

Some animal products like eggs and meat from grass-fed animals may contain small amounts of DHA, but not in high enough quantities to be a primary source. The plant-based omega-3 fatty acid alpha-linolenic acid (ALA), found in flaxseeds and walnuts, can be converted to DHA in the body, but this process is highly inefficient and produces only minimal amounts.

Comparison of DHA Sources


Source	Origin	Primary Form of DHA	Suitable for Vegans?	Potential Contaminants	Bioavailability (Relative)
Fatty Fish	Wild-caught, marine food chain	Triglycerides	No	Mercury, PCBs	High
Algal Oil	Cultivated microalgae	Triglycerides	Yes	Minimal to None	High
Krill Oil	Krill (crustaceans)	Phospholipids	No	Minimal	High
Flaxseed Oil	Flaxseed (plant)	ALA (Precursor)	Yes	Minimal	Low (Conversion)

The Importance of Preformed DHA

Given the low conversion efficiency of ALA to DHA in humans, dietary intake of preformed DHA from marine sources or algal supplements is considered essential for optimal health, especially for specific populations. During pregnancy and infancy, DHA is critical for proper brain and eye development, and maternal intake directly affects the baby's DHA status. Similarly, adequate intake is important for brain health throughout the lifespan, with studies linking low DHA levels to cognitive decline in older adults.

Conclusion

While many people associate DHA with fish, its ultimate source is the microscopic marine algae that form the base of the food chain. This algae is now directly harvested to create sustainable, plant-based DHA supplements, providing a valuable alternative to fish oil for vegetarians, vegans, and those concerned about purity or sustainability. For the general population, both fatty fish and high-quality supplements offer effective ways to obtain this vital omega-3 fatty acid. Understanding the origin of DHA allows for more informed and sustainable dietary choices to support brain, heart, and eye health throughout all stages of life. To learn more about the broader context of omega-3s, you can explore detailed research like the Omega-3 Fatty Acids Review on the National Institutes of Health website.

Frequently Asked Questions

The original source of DHA is marine microalgae, which produce the omega-3 fatty acid as part of their cellular structure. Fish then consume these algae or smaller organisms that have fed on the algae.

Fatty, cold-water fish are the best dietary sources of DHA. Top examples include salmon, mackerel, herring, sardines, and anchovies, which accumulate high levels of DHA from their diet.

Yes, vegetarians and vegans can get preformed DHA from algal oil supplements, which are directly derived from the same microalgae that are the foundational source of omega-3s in the marine food chain. Other plant sources like flaxseed provide ALA, which converts inefficiently to DHA.

While the human body can convert ALA (from plants like flaxseed) into DHA, the conversion rate is extremely low, making it an unreliable source for meeting daily requirements. Direct consumption of DHA from fish or algal oil is far more efficient.

Fish oil is derived from the tissues of fatty fish, while algal oil is sourced directly from cultivated marine microalgae. Algal oil is a plant-based, vegan alternative that bypasses the marine food chain, often containing fewer contaminants.

DHA supplements are generally considered safe for most people when taken within recommended dosage guidelines. However, those with specific health conditions or taking certain medications should consult a healthcare provider, as high doses can thin the blood.

DHA is critical for both fetal and infant brain and eye development, especially during the last trimester of pregnancy and the first few years of life. Maternal intake directly influences the amount of DHA available to the fetus and breastfed infant.