Omega-3 fatty acids have become popular as more and more research points to the variety of health benefits they provide. Yet, despite all the published information about these critical nutrients and the intricate ways they impact our physiology, many resources discuss health outcomes and overlook the molecules responsible. This article will get back to the basics and explore DHA: what it is, what it does, and how much you need to get the most health benefits.

 

Breaking Down DHA 

To understand what docosahexaenoic acid (DHA) is, it’s best to begin with a higher-level explanation of fatty acids. There are two main types of fatty acids: saturated fat and unsaturated fat. The names of these fats refer to their chemical structures, which can impact how they function and their effect on human health. Saturated fats have no double bonds in their carbon chains and are typically solid at room temperature. Unsaturated fats have one or more double bonds in their carbon chains, allowing them to be liquid at room temperature.

Unsaturated fat can be further broken down into monounsaturated fat and polyunsaturated fats. Monounsaturated fats have one unsaturated carbon bond in the molecule, while polyunsaturated fats have more than one. Omega-3 fats are polyunsaturated fatty acids with a double bond located at three carbons from the methyl end of the chain.

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DHA is, specifically, an omega-3 polyunsaturated fatty acid with 22 carbons and six double bonds in the carbon chain. While discussing chemistry may sound boring to many, DHA’s unique chemical structure is what allows it to impact health and biological processes in so many ways.

DHA is considered an essential fatty acid because the human body can only form carbon-carbon double bonds after the ninth carbon from the methyl end of the chain. Therefore, Omega-3s, among a few other dietary fats, are “essential” because we must obtain them from our diet. While polyunsaturated fatty acids can be found in various plant and animal sources, DHA is not naturally present in many foods.

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Where does DHA come from?

DHA is typically found in fish and other seafood sources. However, fish do not actually produce these essential fatty acids. Microalgae are the original producers of omega-3s, like DHA. Phytoplankton then eat the microalgae, small fish eat the phytoplankton, and big fish eat the small fish, allowing DHA to accumulate in the tissue of fish throughout the food chain.

Because omega-3s accumulate in fish based on their diet, the omega-3 content in fish can vary widely based on the food each fish consumes and the fat composition of the fish. For example, cold-water fish, such as salmon and mackerel, have higher fat content and, therefore, higher levels of omega-3s compared to fish with a lower fat content, like tilapia or cod.

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Moreover, while farmed fish usually have higher levels of omega-3s, like DHA, than wild-caught fish, amounts can vary among farm-raised fish based on the food they consume. As if it wasn’t complicated enough, research shows that omega-3 levels in fish have been decreasing over time.

Although it is understood that DHA levels will vary, some of the food sources reported to have the highest amounts of DHA include:

  • Salmon, farmed: 1.24 g per 3 ounces cooked.
  • Salmon, wild: 1.22 g per 3 ounces cooked.
  • Atlantic herring: 0.94 g per 3 ounces cooked.
  • Sardines, canned and drained: 0.74 g per 3 ounces.
  • Salmon, pink, canned and drained: 0.63 g per 3 ounces.

DHA can also be found in supplements. DHA-containing supplements often include fish, krill, cod liver, or algal oils. More information on dietary supplements can be found using the National Institutes of Health Dietary Supplement Label Database. Furthermore, the USDA’s FoodData Central provides the most up-to-date information on foods containing DHA.

After ingesting DHA through food or supplementation, it circulates in the body and is delivered to various tissues, organs, and cells. Omega-3s, like DHA, play essential roles as components of the phospholipids that form cellular membranes. From here, DHA can impact health outcomes.

 

What are Some of the Health Benefits of DHA?

DHA has been reported to affect many seemingly unrelated biological processes, mainly through its effects on cellular membrane fluidity and systemic inflammation. Some of the health benefits linked to DHA include:

  • Brain health throughout the lifespan: DHA is found in high amounts in the brain and is a critical component of neural tissue. An abundance of research has identified the essential role DHA and other omega-3 fats play in brain health, from the development of the brain and central nervous system of fetuses to the reduction of the risk of Alzheimer’s in older adults.
  • Mental health and mood: Data suggest that inadequate omega-3 intake is associated with the development of mood disorders and depressive symptoms. Even more so, omega-3s have been found to play a role in pediatric In line with this evidence, the International Society for Nutritional Psychiatry has even published Research Practice Guidelines for omega-3s in treating major depressive disorder.

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  • Eye health: DHA is vital for infant eye development and continued eye health. Research shows that omega-3 consumption can protect against age-related macular degeneration and may improve signs and symptoms of dry eye.
  • Cardiovascular health: Omega-3s, like DHA, have been found to play a protective role in heart disease. Omega-3 fatty acids have been linked to several beneficial cardiovascular outcomes, such as the reduced risk of stroke incidence, atherosclerotic heart disease, sudden coronary death, peripheral arterial disease, and cardiac remodeling.
  • Pregnancy and preterm birth: Research indicates that pregnant women who consume adequate amounts of omega-3s through food or supplementation have an 11% risk reduction of all-cause preterm birth and a 42% risk reduction of all-cause early preterm birth. Clinical Recommendations have even been developed for this population.
  • Allergy and immunity. Research has found that maternal intake of DHA could reduce an infant’s risk of several allergies and autoimmune conditions, including eczema, asthma, and allergies.

 

How Much DHA do You Need?

While DHA recommendations have not been agreed upon, several health organizations recommend 70-250 mg/day for adults and 200 mg/day for pregnant or lactating women. However, emerging evidence has reported that the amount of DHA consumed might not be the best way to measure adequate intake. Instead, people should pay attention to their Omega-3 Index (O3i).

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The Omega-3 Index represents the omega-3 content of red blood cells expressed as a percent of total fatty acids. Early evidence identified an Omega-3 Index of 8% or more as the optimal level for cardiovascular health benefits, and more recent research continues to confirm these findings. For example, a 2024 study found that DHA levels are significantly and inversely associated with risk of death from all causes and cause-specific deaths due to cardiovascular disease, cancer, and other causes.

Similarly, a 2023 meta-analysis found that omega-3 supplementation did not affect cognitive function. Still, higher baseline Omega-3 Index levels and more significant increases in Omega-3 Index with supplementation were associated with improved cognitive function in older adults. Reports indicate that Omega-3 Index levels in the United States are low, averaging around 5.4%, compared to the recommended 8%. Researchers note that a person might require between 1,000 to 1,600 mg of EPA + DHA daily to increase their Omega-3 Index to the desired levels.

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Summary

DHA is an omega-3 polyunsaturated fatty acid containing 22 carbons and six double bonds. Its chemical structure is a principal reason for its health-promoting properties. Found almost solely in cold water fatty fish, DHA is often under-consumed in the United States. DHA has been associated with several health benefits by influencing systemic inflammation and cellular membrane fluidity.

Some health benefits associated with DHA include brain health for all ages, mental health and mood, eye health, preterm birth, immunity, and cardiovascular health. Although assessing omega-3 intake is beneficial, it is more likely that measuring the Omega-3 Index could provide a better indication of health status. An Omega-3 Index of 8% or higher seems to provide the most health benefits across the board.

These statements have not been evaluated by the Food and Drug Administration. This test is not intended to diagnose, treat, cure, prevent or mitigate any disease. This site does not offer medical advice, and nothing contained herein is intended to establish a doctor/patient relationship. OmegaQuant, LLC is regulated under the Clinical Laboratory improvement Amendments of 1988 (CLIA) and is qualified to perform high complexity clinical testing. The performance characteristics of this test were determined by OmegaQuant, LLC. It has not been cleared or approved by the U.S. Food and Drug Administration.

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