Yes, DHA (docosahexaenoic acid) is one of the three main types of omega-3 fatty acid. The omega-3 family includes ALA, found in plant foods like flaxseed and walnuts; EPA, found primarily in seafood; and DHA, also found in seafood and algae. Of the three, DHA plays the most significant structural role in the human body, concentrating heavily in the brain and retina.
The Three Types of Omega-3
Omega-3 fatty acids aren’t a single nutrient. They’re a family, and each member has a distinct job. ALA (alpha-linolenic acid) is the plant-based form found in foods like flaxseed, chia seeds, and walnuts. Your body treats ALA as a starting material and can technically convert it into EPA and then DHA, but the conversion rate is extremely poor. Less than 0.1% of dietary ALA actually makes it all the way to DHA. That means you can’t reliably get enough DHA from plant-based omega-3 sources alone unless you use an algae-based supplement.
EPA (eicosapentaenoic acid) and DHA are the two “long-chain” omega-3s, both found in fatty fish and shellfish. While they often appear together in food and supplements, they do different things in the body. EPA is primarily involved in cell signaling and managing inflammatory responses. DHA is the structural omega-3: it embeds itself in cell membranes, particularly in brain and eye tissue, and keeps those membranes fluid and functional.
What DHA Does in the Body
DHA concentrates in the brain and retina far more than in other tissues like the heart, liver, or muscles. As a building block of cell membranes, it maintains the flexibility those membranes need to transmit electrical and chemical signals efficiently. This is why DHA matters so much for cognitive function and vision: your brain and eyes rely on rapid, precise signaling between cells, and DHA helps make that possible.
Beyond its structural role, DHA influences processes like the growth of new brain cells, the formation of connections between neurons, and calcium balance in brain tissue. It also has notable anti-inflammatory effects. A study from Tufts University found that DHA lowered the genetic expression of four types of pro-inflammatory proteins, compared to just one for EPA. DHA also reduced white blood cell secretion of three types of inflammatory proteins, while EPA reduced only one. That said, EPA appeared better at maintaining the overall balance between pro-inflammatory and anti-inflammatory signals, so both have value.
DHA During Pregnancy
DHA is especially critical during pregnancy because it accumulates rapidly in the developing fetal brain. The body mobilizes DHA from maternal fat stores and transports it across the placenta, with the most significant buildup happening during the second trimester and the second half of pregnancy overall. This period involves explosive brain growth: new neurons forming, connections branching out, and the early wiring of neural networks. All of these processes depend on having enough DHA available.
Research links higher maternal DHA levels to larger brain volumes and better-developed white matter in children. Insufficient intake during pregnancy may lead to reduced brain volume and impaired neurodevelopment. The American Academy of Pediatrics recommends 1 to 2 servings of DHA-rich fish per week during pregnancy, and the Dietary Guidelines for Americans suggest 8 to 12 ounces of seafood weekly, providing roughly 250 to 400 mg of omega-3s. Clinical trials suggest that moderate doses of 300 to 400 mg per day of DHA may be just as effective as higher doses for supporting fetal brain development. Combined EPA and DHA supplementation up to 5 grams per day is generally considered safe for pregnant and breastfeeding women.
What Happens When DHA Is Low
Because DHA plays such a central role in brain cell membranes, low levels have been linked to a range of mental health and cognitive issues. Dietary deficiencies in omega-3 fatty acids, particularly EPA and DHA, are associated with an increased risk of depression, bipolar disorder, dementia, ADHD, and schizophrenia. The connection likely involves two mechanisms: impaired membrane fluidity in brain cells (which disrupts how receptors and signals function) and increased inflammation in neural tissue.
Most people who eat little to no seafood and don’t take supplements are likely getting very little DHA. Since the body converts less than 0.1% of plant-based ALA into DHA, vegetarians and vegans are at particular risk for low levels unless they supplement with algae-derived DHA.
Best Food Sources of DHA
Fatty fish are by far the richest dietary sources. DHA content per 3-ounce cooked serving varies widely across seafood:
- Herring: 0.77 g
- Canned pink salmon: 0.63 g
- Farmed Atlantic salmon: 0.59 g
- Sardines: 0.45 g
- Atlantic mackerel: 0.43 g
- Rainbow trout (wild): 0.40 g
- Wild Atlantic salmon: 0.35 g
- Oysters: 0.23 g
- Sea bass: 0.18 g
- Shrimp: 0.12 g
Not all fish are created equal. Leaner varieties like cod (0.04 g), yellowfin tuna (0.01 g), and canned light tuna (0.02 g) provide very little DHA. Chicken breast delivers just 0.01 g per serving. If you’re eating fish specifically for DHA, choosing herring, salmon, sardines, or mackerel makes a meaningful difference compared to white fish or shellfish.
For people who don’t eat fish, algal oil supplements are the primary alternative. These are made from the same microalgae that fish get their DHA from in the first place, and they typically provide 100 to 300 mg of DHA per serving. Some also contain EPA.
How DHA Differs From EPA
You’ll almost always see DHA and EPA listed together on supplement labels, but they aren’t interchangeable. EPA is primarily a signaling molecule. It helps regulate inflammatory pathways and plays a balancing role between proteins that promote and resolve inflammation. DHA, on the other hand, is a structural component. It physically integrates into cell membranes and changes how those membranes behave, particularly in the brain and eyes.
Both reduce inflammation, but through different mechanisms and with different metabolic byproducts. The Tufts study found that EPA’s metabolic byproducts were more closely associated with immune regulation, while DHA had a stronger direct anti-inflammatory effect. For brain health, membrane function, and fetal development, DHA is the more relevant of the two. For cardiovascular inflammation and immune balance, EPA plays a larger role. Most health organizations recommend getting both, which is why fish oil supplements typically contain a combination.