DHA, short for docosahexaenoic acid, is a long-chain omega-3 fatty acid that serves as a major structural component of your brain and eyes. It’s one of the most important fats in the human body, concentrated heavily in nerve cell membranes where it supports everything from memory formation to visual processing. Your body can technically make DHA from plant-based omega-3s, but the conversion rate is extremely low, which means most people need to get it directly from food or supplements.
Why Your Body Needs DHA
DHA is not just fuel your body burns for energy. It’s a building block, physically embedded in the membranes of cells throughout your brain and nervous system. At the cellular level, DHA keeps these membranes fluid and flexible, which matters because that flexibility determines how well your brain cells communicate with each other. Stiff, rigid membranes slow down the signaling between neurons. Fluid ones speed it up.
The effects ripple outward into functions you’d recognize. DHA helps form the proteins at synapses (the junctions between brain cells) that enable learning and memory. It also boosts levels of a growth factor called BDNF, which promotes the brain’s ability to adapt, form new connections, and strengthen existing ones. This process, known as neural plasticity, is the biological foundation of learning throughout your entire life. DHA also plays a role in maintaining the protective coating around nerve fibers that keeps electrical signals moving quickly and accurately.
DHA in Your Eyes
The light-sensing cells in your retina contain more DHA than virtually any other cell membrane in the body. That’s not a coincidence. DHA directly affects how efficiently those cells convert light into the electrical signals your brain interprets as vision. When DHA levels in the retina drop, the light-sensing process slows down and becomes less sensitive. Animal research has shown that low omega-3 status reduces the activation of rhodopsin, the key protein that kicks off visual signaling, and delays the chain reaction that follows. In practical terms, adequate DHA supports sharp, responsive vision.
Heart and Blood Vessel Effects
DHA contributes to cardiovascular health through several overlapping mechanisms. It helps lower triglycerides, the most common type of fat circulating in your blood. It also relaxes blood vessel walls by influencing calcium signaling in the smooth muscle cells that line your arteries, which promotes better blood flow.
The blood pressure effects are measurable. A large analysis found that 2 to 3 grams per day of combined omega-3s (DHA plus EPA, its closely related cousin) reduced systolic blood pressure by about 2.6 points in people with normal blood pressure. In people with untreated high blood pressure, the drop was larger: roughly 4.5 points at 3 grams per day. That may sound modest, but at a population level, even small reductions in blood pressure translate to meaningfully lower rates of heart attack and stroke. The American Heart Association recommends about 1 gram per day of combined EPA and DHA for people with existing heart disease.
DHA During Pregnancy and Infancy
Fetal brain development demands a steady supply of DHA, especially during the third trimester when the brain is growing rapidly. Most expert bodies recommend that pregnant women consume at least 250 mg per day of combined DHA and EPA, plus an additional 100 to 200 mg of DHA specifically. The UN’s Food and Agriculture Organization sets a slightly higher floor: at least 300 mg per day of combined omega-3s, with 200 mg coming from DHA.
For women whose DHA intake is particularly low (under 150 mg per day), a recent clinical guideline from the American Journal of Obstetrics & Gynecology recommends 600 to 1,000 mg per day of DHA starting no later than 20 weeks of pregnancy. One consistent finding across trials is that prenatal DHA supplementation reduces the risk of preterm birth, which itself is one of the strongest predictors of developmental delays in children. Some studies have also found higher verbal and full-scale IQ scores in children whose mothers had rising DHA levels during pregnancy, though these effects are difficult to separate from socioeconomic factors.
Why You Can’t Rely on Plant-Based Omega-3s Alone
There are three main omega-3 fatty acids: ALA (found in flaxseed, chia seeds, and walnuts), EPA, and DHA. Your body can convert ALA into EPA and then into DHA, but the process is remarkably inefficient. Most estimates put the conversion rate of ALA to DHA at 2 to 5% in healthy adults. The International Society for the Study of Fatty Acids and Lipids concluded that the true conversion rate in adults is considerably lower than even 1% in infants. This means that eating flaxseed alone won’t meaningfully raise your DHA levels. You need preformed DHA from animal or algal sources.
Best Food Sources of DHA
Fatty cold-water fish are by far the richest dietary sources. A 3-ounce serving of cooked salmon delivers roughly 1,000 to 1,500 mg of combined EPA and DHA, with DHA making up the larger share. Sardines, mackerel, herring, and anchovies are also excellent options. Two servings of fatty fish per week is the standard recommendation for most adults.
If you don’t eat fish, algal oil supplements are the most reliable plant-based alternative. Algae are actually where fish get their DHA in the first place (it accumulates up the food chain), so algal oil provides preformed DHA without the middleman. Most algal oil capsules deliver 200 to 500 mg of DHA per dose. Fish oil supplements are another common option, though the DHA content varies widely by brand, so checking the label for the specific DHA amount (not just total omega-3s) matters.
How Much DHA Do Adults Need?
There is no official recommended dietary allowance for DHA specifically. The Institute of Medicine set adequate intake levels only for ALA, the plant-based omega-3, because it’s technically the only omega-3 classified as essential. In practice, though, most health organizations treat direct DHA intake as important. The FDA allows a qualified health claim on foods and supplements containing EPA and DHA but caps supplement label recommendations at 2 grams per day of combined EPA and DHA.
For the general population, consuming 250 to 500 mg per day of combined EPA and DHA is a widely cited target from multiple international health bodies. People with high triglycerides may benefit from significantly higher doses (up to 4 grams per day of prescription omega-3s), though that level of intake should be guided by a physician. For most people, two servings of fatty fish per week or a daily supplement in the 250 to 500 mg range covers the basics.