DHA: Benefits, Side Effects, Dosage, and Interactions

DHA omega-3

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Docosahexaenoic acid (DHA) is an omega-3 fatty acid essential for brain development during pregnancy and early childhood. It is also linked to improved heart health, better vision, and reduced inflammatory response. 

DHA is naturally produced in small quantities by our bodies, but to achieve adequate amounts, DHA needs to be taken in through dietary sources such as cold-water fish, grass-fed meat, dairy, or omega-3 enriched or pasture-raised eggs. It is also available as supplements, such as fish oil.

The long-chain omega-3 fatty acid is found in cell membranes throughout the body and helps to transmit messages between nerves.

Having adequate levels of DHA makes it easier and more efficient for nerve cells to communicate.

Health Benefits of DHA

DHA is essential for brain development and accounts for 97% of the omega-3 fatty acids found in the brain and 25% of the brain’s total fat content. Research shows it has anti-inflammatory properties and heart health benefits as well. Here’s a closer look.


During pregnancy, women may be advised to take prenatal supplements containing 200mg to 300mg of DHA due to its benefits on brain development. Several studies have found positive associations between DHA supplementation during pregnancy and neurological development in infants.

  • Autism and ADHD: Additional research published in the journal Critical Reviews in Food Science and Nutrition in 2019 shows that higher DHA levels at birth are associated with better childhood neurodevelopmental health, while lower DHA levels were linked to higher rates of autism spectrum disorders and attention-deficit/hyperactivity disorder.
  • Brain development: Another study published in the American Journal of Clinical Nutrition showed children of mothers who supplemented during pregnancy demonstrated better problem-solving abilities during the first year of their life than control subjects whose mothers did not supplement.
  • Eye health: One study, published in the American Journal of Clinical Nutrition, found babies of mothers who supplemented with DHA had better early visual acuity than those whose mothers did not supplement.
  • Full-term births: DHA supplementation during the later weeks of pregnancy is also linked to a decreased risk of early preterm labor. In addition, the DHA pregnancies had lower rates of infants born at 34 weeks or earlier and shorter hospital stays for infants born preterm.

In the study, published in the American Journal of Clinical Nutrition, 350 women were given either 600mg of DHA or a placebo daily during the last half of pregnancy. Women taking the DHA had a longer duration of pregnancy and babies with greater birth weights, lengths, and head circumference than those given a placebo.

DHA in Early Childhood

In the first 6 months of life, DHA is especially important for the development of the nervous system. Breastfeeding mothers are encouraged to continue taking 200mg to 300mg of DHA a day, and most infant formulas also contain DHA. 

This amount must be balanced with the amount of arachidonic acid in the formula as too much DHA might limit the benefits derived from the arachidonic acid which is also essential for healthy development.

Low levels of DHA in early childhood are associated with lower literacy ability, while higher levels are linked to enhanced cognitive development and performance, memory, and speed of performing mental tasks, according to a 2014 study published in the journal Nutrients.

Although study results are mixed, some have shown supplementing with DHA may help to ease the symptoms of ADHD. An article published in 2017 reviewed 16 studies looking at omega-3/6 supplementation and found in 13 studies that supplementation demonstrated favorable effects on ADHD symptoms.

A study published in European Child and Adolescent Psychiatry found 6 months of supplementation with DHA had positive effects on behavioral and cognitive difficulties. Those who took DHA supplements had small improvements in psychosocial functioning, emotional problems, and focused attention. 

DHA for Adults

DHA also provides health benefits for non-pregnant adults, specifically for the following health conditions.

  • Brain health: DHA may help protect against age-related cognitive decline, suggests a 2010 research review from Current Alzheimer's Research. Analyzing data from previously published clinical trials, the review's authors found that taking 900mg supplements containing both DHA and EPA may help treat mild cognitive impairment, but not Alzheimer's disease.
  • Depression: DHA may help protect against depression. Investigators analyzed 14 studies on polyunsaturated fatty acid levels in depressive patients and found people with depression may be more likely to have low levels of DHA and EPA. The study authors suggest that DHA and EPA may reduce depressive symptoms.
  • Heart disease: While there was hope for many years that DHA supplementation might improve outcomes in people with heart disease, more recent evaluation (up to 2017) has not been able to demonstrate a mortality benefit. It does seem to have some efficacy in improving arrhythmias but more studies are needed.

Additional Benefits of DHA

Fish oil is possibly effective in the treatment of several other conditions, including rheumatoid arthritis, menstrual pain, psoriasis, and asthma.

The NIH states that fish oil may help reduce certain forms of cancer (including endometrial cancer). However, it's not known whether taking DHA supplements (as opposed to increasing fish oil intake by consuming oily fish) produces these health benefits.

DHA's Possible Side Effects

Although DHA is generally considered safe, taking DHA in the form of fish oil is known to cause a number of side effects, including bad breath, heartburn, and nausea.

What's more, there's some concern that fish oil might reduce immune system activity and weaken the body's defense against infection. In addition, taking fish oil in combination with certain medications (such as blood pressure drugs) may produce harmful effects in some cases. It's important to consult your physician before combining fish oil with medications.

Fish oil has a blood-thinning effect and should be taken with caution and only after consulting with a physician by people who are on blood thinners or anti-platelet medications.

Dosage and Preparation

DHA is sold as a gel cap supplement or as a liquid. Many dietary supplements contain a combination of DHA and EPA (eicosapentaenoic acid), another omega-3 fatty acid found in fish oil. A typical dose is 5g of fish oil containing 169mg to 563mg of EPA and 72mg to 312mg of DHA.

What to Look For

Widely available for purchase online, DHA supplements are sold in many drugstores, grocery stores, natural-food stores, and stores specializing in dietary supplements. Supplements are not regulated by the FDA. To ensure you are getting a quality brand, look for an independent third-party seal, such as U.S. Pharmacopeia, NSF International, or ConsumerLab.

While taking DHA supplements may offer certain health benefits, it's too soon to recommend DHA as a treatment for any condition. It's important to note that DHA supplements should not be used as a replacement for the standard care of a chronic condition. Avoiding or delaying treatment for a chronic condition in favor of self-treating with DHA may have serious health consequences.

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13 Sources
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