DHA: Benefits, Side Effects, Dosage, and Interactions

DHA omega-3
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In This Article

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, and dairy, and 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 nerves cells to communicate.

Health Benefits

DHA is essential for brain development and accounts for 97 percent of the omega-3 fatty acids found in the brain and 25 percent 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: 

Pregnancy

During pregnancy, women are advised to take prenatal supplements containing 200 mg to 300 mg 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.

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.

Brain Development: Another study published in the American Journal of Clinical Nutrition showed children of mother’s who supplemented during pregnancy demonstrated better problem-solving abilities during the first year of their life than control subjects 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 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.

In addition, the DHA pregnancies had lower rates of infants born at 34 weeks or earlier and shorter hospital stays for infants born preterm.

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.

Early Childhood

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

Low levels of DHA in early childhood is 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.

In addition, research suggests supplementing with DHA may help to ease symptoms of ADHD.

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

Heart Disease

Taking DHA in combination with another omega-3 fatty acid, eicosapentaenoic acid (EPA), may reduce several risk factors for cardiovascular disease (including high cholesterol), according to a 2009 report published in Prostaglandins, Leukotrienes, and Essential Fatty Acids.

In addition, the report's authors note that taking DHA supplements may moderately improve blood pressure and people with higher levels of DHA may have a lower risk of atherosclerosis.

In a 2009 research review published in the American Journal of Therapeutics, scientists found that regular intake of DHA and EPA may significantly reduce the risk of dying from heart disease.

The researchers recommend the following doses under a physician's supervision:

  • Coronary heart disease: 1 g per day of eicosapentaenoic acid and docosahexaenoic acid
  • Hypertriglyceridemia: 3 to 5 g per day of eicosapentaenoic acid and docosahexaenoic acid

Brain Health

Analyzing data from previously published clinical trials, the review's authors found that taking supplements containing both DHA and EPA may help treat mild cognitive impairment, but not Alzheimer's disease. The dose studied was 900 mg a day.

Depression

DHA may help protect against depression, according to a 2010 research review from Biological Psychiatry.

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 help reduce depressive symptoms and, in turn, show promise as an alternative treatment for depression.

Additional Benefits

According to the National Institutes of Health (NIH), fish oil is possibly effective in the treatment of several other conditions, including rheumatoid arthritis, menstrual pain, psoriasis, and asthma.

The NIH also states that fish oil may help reduce the risk of stroke and 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) might help produce these health benefits.

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. Therefore, it's important to consult your physician before combining fish oil with 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 5 grams of fish oil containing 169 mg to 563 mg of EPA and 72 mg to 312 mg 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 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 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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