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DHA (Docosahexaenoic Acid): A Detailed Review by Healthline

DHA (Docosahexaenoic Acid): A Detailed Review

Docosahexaenoic acid (DHA) is one of the most important omega-3 fatty acids.

Like most omega-3 fats, it's linked to many health benefits.

Part of every cell in your body, DHA plays a vital role in your brain and is absolutely crucial during pregnancy and infancy.

Since your body can't produce it in adequate amounts, you need to obtain it from your diet.

This article explains everything you need to know about DHA.

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What is DHA?

DHA is mainly found in seafood, such as fish, shellfish, and fish oils. It also occurs in some types of algae.

It's a component of every cell in your body and a vital structural component of your skin, eyes, and brain.

In fact, DHA comprises over 90% of the omega-3 fatty acids in your brain and up to 25% of its total fat content.

While it can be synthesized from alpha-linolenic acid (ALA), another plant-based omega-3 fatty acid, this process is very inefficient. Only 0.1–0.5% of ALA is converted into DHA in your body.

What's more, the conversion also relies on adequate levels of other vitamins and minerals, as well as the amount of omega 6 fatty acids in your.

Because your body can't make DHA in significant amounts, you need to get it from your diet or take supplements.

SUMMARY DHA is vital for your skin, eyes, and brain. Your body can't produce it in adequate amounts, so you need to obtain it from your diet.

How does it work?

DHA is mainly located in cell membranes, where it makes the membranes and gaps between cells more fluid. This makes it easier for nerve cells to send and receive electrical signals.

Therefore, adequate levels of DHA seem to make it easier, quicker, and more efficient for your nerve cells to communicate.

Having low levels in your brain or eyes may slow the signaling between cells, resulting in poor eyesight or altered brain function.

SUMMARY DHA makes the membranes and gaps between nerve cells more fluid, making it easier for cells to communicate.

Top food sources of DHA

DHA is mainly found in seafood, such as fish, shellfish, and algae.

Several types of fish and fish products are excellent sources, providing up to several grams per serving. These include mackerel, salmon, herring, sardines, and caviar.

Some fish oils, such as cod liver oil, can provide as much as 1 gram of DHA in a single tablespoon (15 ml).

Just keep in mind that some fish oils may also be high in vitamin A, which can be harmful in large amounts.

What’s more, DHA may occur in small amounts in meat and dairy from grass-fed animals, as well as omega 3 enriched or pastured eggs. 

However, it may be hard to get enough from your diet alone. If you don't regularly eat these foods, taking a supplement may be a good idea.

SUMMARY DHA is mostly found in fatty fish, shellfish, fish oils, and algae. Grass-fed meat, dairy, and omega-3-enriched eggs may also contain small amounts.

Effects on the brain

DHA is the most abundant omega-3 in your brain and plays a critical role in its development and function.

Brain levels of other  omega 3  fatty acids, such as EPA, are typically 250–300 times lower.

Plays a major role in brain development

DHA is extremely important for brain tissue growth and function, especially during development and infancy.

It needs to accumulate in the central nervous system for your eyes and brain to develop normally.

DHA intake during the third trimester of pregnancy determines the baby's levels, with the greatest accumulation occurring in the brain during the first few months of life.

DHA is mainly found in the gray matter of the brain, and the frontal lobes are particularly dependent on it during development.

These parts of the brain are responsible for processing information, memories, and emotions. They are also important for sustained attention, planning, problem solving, and social, emotional, and behavioral development.

In animals, decreased DHA in a developing brain leads to a reduced amount of new nerve cells and altered nerve function. It also impairs learning and eyesight.

In humans, DHA deficiency in early life has been associated with learning disabilities, ADHD, aggressive hostility, and several other disorders.

Furthermore, low levels in mothers are linked to an increased risk of poor visual and neural development in the child.

Studies show that babies of mothers who consumed 200 mg per day from the 24th week of pregnancy until delivery had improvements in vision and problem solving.

May have benefits for the aging brain

DHA is also critical for healthy brain aging.

As you age, your brain goes through natural changes, characterized by increased oxidative stress, altered energy metabolism, and DNA damage.

The structure of your brain also changes, which reduces its size, weight, and fat content.

Interestingly, many of these changes are also seen when DHA levels decrease.

These include altered membrane properties, memory function, enzyme activity, and neuron function.

Taking a supplement may help, as DHA supplements have been linked to significant improvements in memory, learning, and verbal fluency in those with mild memory complaints.

Low levels are linked to brain diseases

Alzheimer's disease is the most common form of dementia in older adults.

It affects about 4.4% of people over age 65 and alters brain function, mood, and behavior.

Reduced episodic memory is among the earliest signs of brain changes in older adults. Poor episodic memory is associated with difficulties recalling events that occurred at a specific time and place.

Interestingly, Alzheimer's disease patients have lower amounts of DHA in the brain and liver, while EPA and docosapentaenoic acid (DPA) levels are elevated.

Studies show that higher blood DHA levels are linked to a reduced risk of dementia and Alzheimer's.

SUMMARY DHA is essential for brain and eye development. As such, low levels may disrupt brain function and are linked to an increased risk of memory complaints, dementia, and Alzheimer's disease.

Effects on eyes and vision

DHA helps activate rhodopsin, a membrane protein in the rods of your eyes.

Rhodopsin helps your brain receive images by changing the permeability, fluidity, and thickness of your eye membranes.

A DHA deficiency can cause  vision problems, especially in children.

Therefore, baby formulas are now generally fortified with it, which helps prevent vision impairment in babies.

SUMMARY DHA is important for vision and various functions inside your eye. A deficiency may cause vision problems in children.

Effects on heart health

Omega-3 fatty acids are generally linked to a reduced risk of heart disease.

Low levels are associated with an increased risk of heart disease and death, and some studies show that supplements reduce your risk.

This applies especially to the long-chain omega-3 fatty acids found in fatty fish and fish oils, such as EPA and DHA.

Their intake can improve many risk factors for heart disease, including:

  • Blood triglycerides. Long-chain omega-3 fatty acids may reduce blood triglycerides by up to 30%.
  • Blood pressure. The omega-3 fatty acids in fish oils and fatty fish may reduce blood pressure in people with high levels.
  • Cholesterol levels. Fish oils and omega-3s may lower total cholesterol and increase HDL (good) cholesterol in people with high levels.
  • Endothelial function. DHA may protect against endothelial dysfunction, which is a leading driver of heart disease.

While some studies are promising, many don’t report any significant effects. 

Two large analyses of controlled studies concluded that omega-3 fatty acids have minimal effects on your risk of heart attacks, strokes, or dying from heart disease. 

SUMMARY DHA may reduce your risk of heart disease by lowering blood triglycerides and blood pressure, among other effects. However, its role in heart disease prevention is controversial. 

Other health benefits

DHA may also protect against other diseases, including:

  • Arthritis. This omega-3 reduces inflammation in your body and may alleviate pain and inflammation related to arthritis.
  • Cancer. DHA may make it more difficult for cancer cells to survive.
  • Asthma. It may reduce asthma symptoms, possibly by blocking mucus secretion and reducing blood pressure.

SUMMARY DHA may relieve conditions like arthritis and asthma, as well as prevent the growth of cancer cells.

Especially important during early life

DHA is critical during the last months of pregnancy and early in a baby's life.

Babies up to the age of 2 have a greater need for it than older children and adults.

As their brains are growing rapidly, they need high amounts of DHA to form vital cell membrane structures in their brains and eyes.

Therefore, DHA intake can dramatically affect brain development.

Animal studies show that DHA-deficient diets during pregnancy, breastfeeding, and weaning limit the supply of this omega-3 fat to the infant's brain to only about 20% of normal levels.

Deficiency is associated with changes in brain function, including learning disabilities, alterations in gene expression, and impaired vision.

SUMMARY During pregnancy and early life, DHA is vital for the formation of structures in the brain and eyes.

How much DHA do you need?

Most guidelines for healthy adults recommend at least 250–500 mg of combined EPA and DHA per day.

Studies show the average DHA intake is closer to 100 mg per day.

Children up to the age of 2 may need 4.5–5.5 mg per pound of body weight (10–12 mg/kg), while older children may need up to 250 mg per day.

Pregnant or breastfeeding mothers are advised to get at least 200 mg of DHA, or 300–900 mg of combined EPA and DHA, per day.

People with mild memory complaints or cognitive impairments may benefit from 500–1,700 mg of DHA per day to improve brain function.

Vegetarians and vegans are often lacking in DHA and should consider taking microalgae supplements that contain it.

DHA supplements are usually safe. However, taking more than 2 grams per day does not have any added benefits and is not recommended.

Interestingly, curcumin, the active compound of turmeric, may enhance your body’s DHA absorption. It's linked to many health benefits, and animal studies suggest that it may boost DHA levels in the brain.

Therefore, curcumin may be helpful when supplementing with DHA.

SUMMARY Adults should get 250–500 mg of combined EPA and DHA daily, while children should get 4.5–5.5 mg per pound of body weight (10–12 mg/kg).

Considerations and adverse effects

DHA supplements are usually well tolerated, even in large doses.

However, omega-3s are generally anti-inflammatory and may thin your blood. Consequently, too much omega-3 may cause blood thinning or excessive bleeding.

If you are planning surgery, you should stop supplementing with omega-3 fatty acids a week or two beforehand.

Additionally, consult with your healthcare practitioner before taking omega-3s if you have a blood clotting disorder or take blood thinners.

SUMMARY Like other omega-3 fatty acids, DHA may cause blood thinning. You should avoid taking omega-3 supplements 1–2 weeks before surgery.

The bottom line

DHA is a vital component of every cell in your body.

It's essential for brain development and function, as it may affect the speed and quality of communication between nerve cells.

Furthermore, DHA is important for your eyes and may reduce many risk factors for heart disease.

If you suspect you're not getting enough in your diet, consider taking an omega 3 supplement.