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Health Benefits of DHA: An Omega-3 Fatty Acid in Fish and Algae

Updated on August 9, 2017
AliciaC profile image

Linda Crampton is a teacher with a first class honors degree in biology. She writes about human biology and the scientific basis of disease.

Wild salmon is a good source of DHA, but it isn't an acceptable food for vegans or vegetarians.
Wild salmon is a good source of DHA, but it isn't an acceptable food for vegans or vegetarians. | Source

What Is DHA?

Docosahexaenoic acid, or DHA, is an omega-3 fatty acid found in oily fish. Like EPA (eicosapentaenoic acid), another omega-3 fatty acid in fish, DHA has some valuable health benefits. Since nutritionists often refer to DHA and EPA at the same time, to the general public it may seem like the nutrients have identical effects in our body. Docosahexaenoic acid offers special benefits, however.

While oily fish are the best source of DHA, there are other sources which can be helpful for vegetarians and vegans. Vegetarians eat plants, dairy foods, and eggs, but no fish or meat. Vegans eat no food that comes from animals.

Some vegetarian and vegan foods are enriched or fortified with DHA, EPA, or both of these nutrients. DHA is produced by certain types of algae and can be purchased in health food stores. The omega-3 fatty acid in plants is most commonly alpha-linolenic acid, or ALA. ALA can be converted to DHA and EPA in our bodies, although this conversion isn't very efficient.

Sardines are a good source of omega-3 fatty acids.
Sardines are a good source of omega-3 fatty acids. | Source

DHA Health Benefits in Humans

When investigating the health benefits of DHA, it's important to distinguish hype from facts and to get information from independent and authoritative websites instead of (or as well as) from the websites of companies that sell docosahexaenoic acid.

A report on health claims for DHA has been created by the European Food Safety Authority (EFSA). The report is based on the analysis of scientific research and reaches the following conclusions about the nutrient's benefits. Docosahexaenoic acid is said to:

  • lower the level of blood triglycerides if taken in a sufficient daily dose
  • help maintain normal brain function (a "well-established" benefit)
  • help maintain the health of the retina and normal vision (also a well-established benefit)

The EFSA considers the following proposed benefits of DHA to be unproven.The chemical may or may not:

  • reduce the level of oxidized cholesterol
  • help to maintain normal weight
  • help to maintain normal sperm mobility

Hemp seed oil is a good source of omega-3 fatty acids that can be converted into DHA and EPA.
Hemp seed oil is a good source of omega-3 fatty acids that can be converted into DHA and EPA. | Source

Lowering Triglycerides

A triglyceride is a fat molecule. Although too many triglycerides are unhealthy, they are vital molecules. They are normally stored in fat cells and provide our body with energy when needed.

A high level of triglycerides in the blood is known as hypertriglyceridemia. The condition is dangerous because it increases the risk of heart disease and strokes. DHA has been shown to lower a high triglyceride level.

Helping Brain and Eye Function

DHA is incorporated into the phospholipid molecules in cell membranes, especially those of our brain cells and retina cells. The retina is the light-sensitive layer at the back of the eyeball. DHA is thought to help the membranes function properly.

DHA is beneficial for brain function and cognition as well as sight. It seems to be very important in the outer membranes of neurons (nerve cells), especially in those involved in the transmission of nerve impulses from one neuron to another.

Flax seeds are a great source of ALA, which can be converted into DHA.
Flax seeds are a great source of ALA, which can be converted into DHA. | Source

Improving Memory

There are other suspected health benefits of DHA. A link between an adequate amount of the chemical in the diet and improved memory has often been observed.

A team of researchers at the University of Alberta discovered that lab animals fed a diet high in docosahexaenoic acid stored more of the substance in the hippocampus area of their brain, which plays an important role in memory. They also found that the cells in the hippocampus could communicate with each other better when more DHA was present. These processes might explain why the chemical seems to improve memory. The amount of DHA in the brain decreases with age, so ensuring that the diet contains this nutrient may help to maintain memory as we grow older.

A low brain level of docosahexaenoic acid seems to be a risk factor for Alzheimer's disease. As yet, it's unknown if the nutrient can treat the disease.

A Registered Dietitian Discusses DHA Benefits

Improving Mental Health

A group of scientists investigated the level of omega-3 fatty acids in 800 military service members who had committed suicide and in 800 service members who hadn't committed suicide. The two groups were matched with respect to gender, age, and rank.

The scientists found that all of the people tested had a low level of omega-3 fatty acids in their body. They also found that the suicide risk was greatest in people who had the lowest level of DHA. Previous research has also suggested that the level of docosahexaenoic acid may be significant in some mental health problems.

Many people enjoy eating salmon, which contains both DHA and EPA.
Many people enjoy eating salmon, which contains both DHA and EPA. | Source

Benefits in Liver Disease

As obesity increases in North America, so does the incidence of liver disease. According to the American Liver Foundation, about 25% of the U.S. population have nonalcoholic fatty liver disease. This includes about 75% of the obese population. Fatty liver disease may progress to more serious disorders, including cirrhosis of the liver, liver cancer, and a condition known as nonalcoholic steatohepatitis, or NASH. All of these disorders may be fatal.

When a person develops NASH, the liver becomes scarred during a process called fibrosis. Fibres made of protein collect in the scarred areas. In studies involving lab animals, researchers found that DHA reduced the level of proteins found in NASH fibrosis by more than 65%. EPA had "comparatively little" effect on the protein level.

Halibut contains omega-3 fatty acids.
Halibut contains omega-3 fatty acids. | Source

Benefits in Fetal Development

DHA passes through the placenta from a woman to her fetus and is essential for the development of the baby's brain and vision. DHA supplements are often recommended for pregnant women for this reason. However, some research suggests that the fetus gets all of the DHA that it needs from its mother's body—even without supplementation—and that supplementation isn't beneficial. Other research suggested that DHA supplementation is helpful for a developing baby, although some of the research doesn't differentiate between DHA and EPA. This is an area that needs much more investigation.

Once the baby is born, he or she continues to receive DHA through the mother's milk. Docosahexaenoic acid is added to many infant formulas for those babies who don't drink milk made by their mother.

DHA in Pregnancy and Lactation

Pregnant and lactating women should seek their doctor's advice about DNA supplementation and about the use of any other supplements.

Krill contain omega-3 fatty acids.
Krill contain omega-3 fatty acids. | Source

Sources of DHA

Oily Fish and Krill

The best way to get DHA is in the diet. Oily fish such as wild salmon, some tuna, sardines, herring, and mackerel are very good sources of both EPA and DHA. Krill are also a good source. Krill are small crustaceans that live in oceans around the world and are part of the plankton.

There are potential problems with getting omega-3 fatty acids from fish or krill. In order for the animals to be a wise food choice, they need to be low in mercury. Mercury is an ocean pollutant and is toxic to humans. In addition, the fishing industry used to harvest the animals needs to be sustainable.

Enriched and Fortified Food

Some eggs contain a higher than normal level of omega-3 fatty acids. DHA and/or EPA are added to some varieties of milk, orange juice, and breakfast cereals. A consumer should investigate the type and source of omega-3 fatty acids in enriched and fortified foods. For example, some chickens that produce enriched eggs are fed fish oil. This may be considered unacceptable by vegetarians and vegans.


Certain microscopic marine algae, or microalgae, produce DHA. The algal cells are cultured in a special facility and then processed to extract their oil. The oil is rich in DHA and is free of ocean pollution. It's popular with some vegans since it's obtained without killing animals.


Some people obtain omega-3 fatty acids by taking fish oil supplements instead of algal oil supplements. It's important that the correct dose of a supplement is taken. Too much could be dangerous, while too little could have no effect on the body. The purity and freshness of the oil also need to be considered.

Some omnivores take gelatin capsules filled with fish oil as a supplement.
Some omnivores take gelatin capsules filled with fish oil as a supplement. | Source

An Omega-3 Poll

Do you take an omega-3 supplement?

See results
Docosahexaenoic acid is important for brain function.
Docosahexaenoic acid is important for brain function. | Source

Docosahexaenoic Acid Research

Tantalizing observations suggest that docosahexaenoic acid may have wonderful health benefits, but the results of some experiments with the chemical have been disappointing. More research is needed to clarify the functions of DHA in our bodies. Some questions that need to be answered are listed below.

  • How do DHA's effects differ from EPA's effects?
  • Does DHA have different effects at different times in our lives or in different stages of fetal development?
  • Does it need other nutrients in order to function best?
  • What dose is helpful and what dose is harmful?
  • Is DHA more beneficial in food than in supplements, or vice versa?

Despite some uncertainty about the actions of docosahexaenoic acid, the evidence obtained so far indicates that it's a valuable nutrient. Ensuring that our diet contains adequate amounts of this nutrient is definitely worthwhile.


Scientific Report from the European Food Safety Authority (EFSA): This report is available as a PDF file at the Wiley Online Library. The link to the file is on the EFSA site.

University of Alberta Faculty of Medicine & Dentistry. (2012, June 28). Why does a diet high in DHA improve memory?. ScienceDaily. Retrieved July 30, 2017 from

Docosahexaenoic Acid and Liver Fibrosis from Oregon State University

DHA and Suicide Risk from the NIH (National Institutes of Health)

© 2013 Linda Crampton


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    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      Hi, Peggy. Yes, "brain food" is a good name for fish that contain DHA! Thank you for the visit and the comment.

    • Peggy W profile image

      Peggy Woods 4 years ago from Houston, Texas

      Interesting article Alicia. I eat sardines occasionally but my husband and I both enjoy and eat salmon quite frequently. He takes fish oil supplements and I take the krill oil supplements because they are smaller and easier to swallow. Good to know that all of this is good for memory. Our mothers were right when they said that "fish is brain food." :)

    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      Thanks for the visit, Dianna. I like sardines, too, as well as salmon. It is good to know that they are healthy foods.

    • teaches12345 profile image

      Dianna Mendez 4 years ago

      My hubby loves sardines, so I am glad to see they are a great source of Omega 3. I do take a supplement for this, good to know how much they benefit the body and brain. Thanks for the information.

    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      It's great when someone enjoys a food that's good for them! Thanks for the comment, mylindaelliot.

    • mylindaelliott profile image

      mylindaelliott 4 years ago from Louisiana

      Those are all good reasons to enjoy food that I already like.

    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      Hi, Kathi. Thanks for the visit and the comment. Salmon patty sandwiches sound very tasty. DHA's health benefits are interesting, and eating salmon can be a great way to get them!

    • Fossillady profile image

      Kathi 4 years ago from Saugatuck Michigan

      Thank you for the high quality information Alicia. Lately, I have included more salmon in my diet with salmon patty sandwiches. They are tasty minus the overpowering fishiness. Interesting about the suicide rate . . . how bazaar. Good to know it improves memory, sure can use that. lol Kathi :O)

    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you, JCielo. I appreciate your comment very much! Your advice about choosing an omega-3 oil supplement is excellent.

    • JCielo profile image

      JCielo 4 years ago from England

      My wife and I both take Krill oil supplements. But, as with all supplements, you have to ensure that you get the very best quality and have some confidence about where the 'ingredients' are sourced.

      This is a very important topic that has been very well researched and written in a clear, concise manner. Loved it. Congrats!

    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you very much, Deb. I appreciate your comment! It is a big problem that we can't tell how much mercury a particular piece of fish contains before we eat it. All we can do is stick to the types of fish that researchers say are generally safe to eat. Luckily, salmon is one of these fish.

    • aviannovice profile image

      Deb Hirt 4 years ago from Stillwater, OK

      New studies definitely bear watching. It may also be hard to discern wild salmon from other types, and whether or not mercury is present. A wonderful piece, with definite food for thought. Great work!

    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      Good luck with the new baby, leahlefler! I hope all goes according to plan. DHA is certainly an interesting and useful substance. I hope researchers learn more about it soon. Thanks for the comment.

    • leahlefler profile image

      Leah Lefler 4 years ago from Western New York

      When I was pregnant with my first two boys, prenatal vitamins didn't include DHA. We're trying to conceive at the moment, and the prenatal vitamins come with an additional DHA supplement - this hub shows why it is so important! I love grilled salmon, so here's another positive reason to eat it!

    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      They are tricky words - they don't exactly roll off the tongue! Thank you very much for the visit and the comment, drbj.

    • drbj profile image

      drbj and sherry 4 years ago from south Florida

      All I know, Alicia, is that anyone ... like you, m'dear ... who can correctly spell the correct words for the two omega-3 fatty acids - DHA and EPA - is my kind of researcher. Trust me.