Docosahexaenoic acid (DHA), a major omega-3 fatty acid found in fish, seafood, and fish oil supplements, is an extensively researched and popular supplement ingredient. As one of the most commonly used supplements worldwide, fish oil has shown promising benefits for improving high cholesterol and high blood pressure, enhancing cognitive function in adults, and promoting normal fetal, infant, and child brain development. (5) It’s best to obtain DHA from dietary sources; however, some individuals, particularly those who avoid fish and seafood, may be advised to take a daily supplement containing DHA. Read on to learn more about Docosahexaenoic acid (DHA) and its benefits.
What is DHA?
Docosahexaenoic acid (DHA) is a type of omega-3 fatty acid and long-chain polyunsaturated fatty acid that’s naturally found in fish and seafood. DHA is an essential structural component of cell membranes and is present in significant amounts in the brain and retinas of the eyes. (9) Although fish and seafood are the primary dietary sources of DHA, this essential fatty acid originates from microalgae. When fish and shellfish consume plankton that feed on microalgae, the omega-3s accumulate in their tissues. (18)
How much DHA do you need?
The Food and Nutrition Board of the Institute of Medicine (IOM) has not established adequate intakes (AIs) for total omega-3s, DHA, or eicosapentaenoic acid (EPA), another prominent type of omega-3 found in fish and seafood. Instead, they’ve instituted specific intake recommendations for a third type of omega-3 fatty acid, alpha-linolenic acid (ALA), which is converted to EPA and DHA in the body. ALA is considered essential, meaning it can’t be produced by the body and must be consumed. The top sources of ALA include flaxseed oil, chia seeds, and walnuts. (18) The table below outlines the AIs for omega-3s as ALA.
Did you know? Some health organizations recommend that adults consume at least 500 mg (0.5 g) of combined EPA and DHA per day; however, there isn’t an established AI for EPA or DHA at this time. (20)
While ALA converts to DHA and EPA, the conversion rate is very low, and consequently, relying on dietary sources of ALA may not be enough to supply the body with enough DHA for optimal health. Research demonstrates that the conversion rate of ALA to DHA is only approximately 0.5 to 9%. (3)(4)(8)(19) For this reason, EPA/DHA supplements may be recommended, especially if you don’t regularly consume fish and seafood.
Are you vegan or vegetarian? Plant-based algal oil supplements containing DHA have been shown to increase DHA concentrations in individuals who don’t consume fish or seafood. (6)
Docosahexaenoic acid sources
DHA can be found in various sources, including:
- Salmon, farmed – 1.24 g per 3 oz
- Salmon, wild – 1.22 g per 3 oz
- Sardines – .74 g per 3 oz
- Mackerel – .59 g per 3 oz
- Salmon, canned – .63 g per 3 oz
- Rainbow trout, wild – .44 g per 3 oz
- Oysters – .23 g per 3 oz
- Sea bass – .47 g per 3 oz
- Shrimp – .12 g per 3 oz (18)
Did you know? DHA and EPA are included in most fish oil supplements and are often regarded as a single entity; however, research suggests that the two may have slightly different benefits. (10)
1. Heart health
When taken in combination with EPA, DHA has been shown to reduce blood pressure in individuals with hypertension (high blood pressure), a risk factor for cardiovascular disease. (16) A 2019 randomized controlled trial compared the blood pressure lowering effects of EPA, DHA, and olive oil (a plant-based source of monounsaturated fat), when used independently. After 12 weeks of daily supplementation, DHA and olive oil were more effective than EPA in lowering systolic and diastolic blood pressure. (14)
Studies demonstrate that fish oil supplements may also improve lipid levels in individuals with high concentrations of certain fats (lipids) in the blood, a condition known as hyperlipidemia. Research comparing EPA and DHA taken in isolation demonstrates that DHA may be more effective than EPA at reducing the proportion of smaller low-density lipoprotein (LDL) particles and increasing mean LDL particle size. Why is this significant? The presence of smaller, more dense LDL particles pose a greater risk of cardiovascular disease compared to larger particles. (1) DHA may also be superior to EPA at reducing serum triglycerides, a type of fat in the blood that, when elevated, can be a risk factor for cardiovascular disease and stroke. (13)(17)
The American Heart Association (AHA) and the Dietary Guidelines for Americans recommend one to two servings of seafood per week to reduce the risk of cardiovascular disease. The AHA also recommends that individuals with existing coronary heart disease consume approximately 1 g per day of EPA/DHA from oily fish; however, supplements can also be considered if recommended by your practitioner. (18)
2. Cognitive function
Research suggests that individuals with greater consumption of marine-derived DHA are less likely to develop dementia and Alzheimer’s disease. (24) In fact, some observational studies have demonstrated that individuals who eat fish or seafood each week and/or have high levels of DHA are at a lower risk of dementia. (7)(12)(24)
DHA supplements, used alone or in combination with EPA, may contribute to improved memory function. A systematic review and meta-analysis concluded that DHA/EPA supplements may improve episodic memory outcomes in older adults reporting mild memory complaints. These protective benefits are believed to be driven by DHA, particularly in doses above 1 g per day. (23)
DHA may also improve cognitive performance in healthy young adults. One trial noted that DHA supplementation improved memory and reaction time in individuals whose diets were low in DHA. (21)
3. Infant and child development
DHA is vital for normal brain and eye function and the development of neural tissues, all of which contribute to motor and cognitive development in children. (2) Although the body can synthesize DHA from ALA, fetuses don’t have this ability. (9) During pregnancy, DHA transfers across the fetal blood–brain barrier to the fetus. The amount of DHA that crosses through the fetal blood–brain barrier is dependent on maternal dietary intake of DHA. (2)
Consuming adequate DHA through diet and/or supplementation during pregnancy and while breastfeeding has been shown to have significant positive effects on infant brain development. A 2018 study identified a positive association between maternal DHA status during pregnancy and enhanced problem-solving skills in infants at one year of age. (2)
Omega-3 supplementation, particularly DHA, during pregnancy has been shown to reduce the relative risk for early preterm birth before 34 weeks of gestation by 42% and preterm birth before 37 weeks by 11%. Furthemore, DHA was shown to reduce the relative risk of low birth weight by 10%. (15)
Did you know? Approximately 95% of pregnant women and women of child-bearing age don’t consume enough omega-3 fatty acids. (9)
The bottom line
Docosahexaenoic acid (DHA) has been shown to positively affect heart health, cognitive function, and infant brain development. Diets rich in fish and seafood are likely to provide adequate amounts of DHA; however, individuals who avoid these foods or don’t regularly consume them may benefit from a fish oil supplement. If you’re a patient, consult your integrative healthcare provider before introducing new supplements to your wellness plan.
Download a handout on omega-3 fatty acids.
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