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6 Benefits of Docosahexaenoic acid (DHA)

Written on February 10, 2022

What it is | How it worksDHA and EPA | Benefits | How to take | Precautions and Side Effects | Buyer’s Guide | The Bottom Line

What it is

Docosahexaenoic acid (DHA) is an omega 3 fatty acid that has been linked to improved cardiovascular health and cognitive function.

Docosahexaenoic acid is crucial for eye and brain health.

It is also important for nervous system function and may reduce dementia risk.

Pregnant women and infants have high DHA requirements for optimal development and growth.

DHA can be found in many foods including salmon, tuna, trout, oysters and clams.

The Best DHA Supplements

In general, Omega-3 supplements have a wide range of quality so it is crucial you buy the best products available. In order to produce a consistent fish oil product, numerous optimal manufacturing processes are required to control for total oxidation and heavy metal content. We’ve identified a few of the best supplements below.


Nov 2023 Update: Look for IFOS accredited supplements from brands like OmegaVia and Carlson’s

How it works

An omega-3 polyunsaturated fatty acid, DHA influences membrane structure, cell signalling and gene expression.

Dietary sources of DHA form the majority of DHA in the body.

However, the human body can produce DHA from ALA.

This metabolic pathway involves numerous steps, including a series of enzyme-catalysed elongation and desaturation reactions.

These reactions primarily occur in the liver and to a lesser extent the brain [1].

ALA is an essential fatty acid synthesised in plants and in many lower organisms.

The difference between DHA and EPA

An omega-3 fatty acid, EPA helps reduce inflammation in the body.

EPA has been shown to have a larger effect on moderating systemic inflammation than DHA [2].

DHA is important for brain development and visual function [3].

In terms of anti-inflammatory effect, DHA has a lower effect than EPA because it doesn’t reduce arachidonic acid, an inflammation modulator [4].

The reason DHA is not an inhibitor of arachidonic acid is because it can’t undergo certain reactions.

EPA on the other hand, can undergo these reactions due to its structure.

DHA has 22-carbons compared to 20 in EPA.


IN DEPTH: Why does EPA inhibit arachidonic acid (an inflammation cause)?

Reason 1: EPA inhibits the enzyme delta-5-desaturase that is involved in producing arachidonic acid

Reason 2: Where DHA cannot, 20-carbon EPA can compete with arachidonic acid for phospholipase A2. Phospholipase A2 is required to release arachidonic acid from the membrane it is stored

Because EPA levels in the brain are low, it is assumed that it is not important for brain health however this is incorrect.

EPA is still found in the brain, however it is rapidly oxidised [5].

By competing with AA for enzyme production, EPA is vital in reducing inflammation in the brain.

This has led many to incorrectly determine that EPA is less important than DHA for brain health.


1. May reduce anger and hostility

DHA at high doses may help reduce the incidence of hostile behaviour and anger.

One study found that university students (n=41) taking DHA at a dose of 1.5g/day for 90 days were less hostile compared to placebo.

During periods of normal stress prior to the treatment, 27% of students had hostile responses to a stressor.

During final exams, a stressful period, hostile responses rose to 92%.

In those taking 1.5grams/day of DHA, there was no increase in hostility.

Therefore, taking DHA can improve our emotional control when we are stressed and improve our mood.

2. Improves learning ability and ADHD symptoms

Taking DHA can improve attention and learning in people of all ages, especially those with ADHD [6].

Omega-3 deficiencies have also been found to alter dopamine and serotonin activity [7].

Low levels of DHA in children have been linked to certain developmental and behavioural disorders including ADHD and dyslexia [8].

Higher DHA levels at birth are associated with better childhood brain development [9].

Autism spectrum disorders and attention-deficit hyperactivity disorder have been linked to lower DHA status at birth.

Prenatal supplementation indicate that DHA levels are influenced by other factors such as socio-economic conditions.

3. May reduce dementia risk

As you age, your memory regresses and you experience reductions in neurotransmitter levels.

Specifically, serotonin, acetylcholine and dopamine.

DHA can help prevent this by increasing neurotransmitter release in the hippocampus.

In one study, those in the top quartile of DHA (levels) had a 47% reduction in all-cause dementia [10].

4. May protect against depression

DHA can protect against depression however it may need to be combined with EPA for potency.

The literature is conflicting and in many cases DHA alone fails to outperform placebo when considering depressive symptoms [11][12].

This suggests that DHA:EPA ratio is important and accounting for EPA intake is also necessary.

In general, fish oil supplementation only improved depression for those with major depression.

Low intake of fatty fish during pregnancy has been associated with depression [13].

5. Plays a crucial role in fetal and infant development

Fetal and infant brain development occurs during brain growth spurts from the third trimester of pregnancy to 1.5 years after birth.

The weight of the brain increases from 100 g at 30 weeks of gestation to 1.1kg at 18 months of age [14].

Over this time, the DHA content of the brain increases from 90 mg to 3,300 mg [15].

This represents a 35-fold increase in brain DHA levels.

It has been observed that women are much more efficient at converting ALA. This may be due to the greater requirement to produce DHA during pregnancy [16].

Infants have been found to be more efficient than adults at converting ALA to DHA [17].

Compared to control group, women eating salmon during pregnancy (twice per week from week 20 of pregnancy until birth) had more DHA in their breast milk [18].

Regularly incorporating fatty fish into your diet can have benefit for both your health and the health of your child.

6. Improves microbiome health and reduces inflammation

The gut microbiome is extremely important for your immune system and health.

Gut microbes play a vital role in specifically maintaining our intestinal health.

DHA has been shown to improve the diversity of gut microbiota, and exerts an inhibitory effect on a variety of bacteria [19].

In middle aged women, omega-3 fatty acids correlate with gut microbiome diversity [20].

Further studies examining whether it is DHA affecting microbiome diversity or the other way round are necessary.

However the conclusion that it is DHA in particular that results in higher microbiome diversity is consistent with recent clinical trials in obese individuals [21][22].

How to take

From 0.5g per day up to 1.6g/day as this amount has been safely tolerated in long-term scenarios.

Precautions and Side effects

Side effects are rare and DHA is likely safe.

Larger than normal doses of DHA can thin your blood so those who are taking blood-thinning drugs or have planned surgery should consult their doctor [23].

Buyer’s Guide

At Nootritious, we are frustrated with the options people have in choosing nootropics.

The way we choose supplements in our buyer’s guide is the same process that we undertake when choosing for our family and loved ones.

We aim to clarify the best option amongst the vast variety of supplements through consideration of the product and independent tests during our research process.

When it comes to buying DHA supplements, fish oils may provide the best bang for buck, both in terms of efficacy and value.

Fish oils contain EPA and DHA.

The net effect is synergistic, however fish oils can suffer from issues related to contamination with mercury and oil oxidation.


DHA and EPA are vital for your health and insufficient intake can lead to adverse health outcomes.

Fish oils are a suboptimal solution for a diet rich in oily fish however have shown to be effective in studies.

DHA is crucial especially in early infants.

When purchasing a DHA supplement, look for mercury contamination and PCB/oil oxidation levels.

The conversion of ALA to DHA is less efficient in adult men, so supplementation can be helpful.