Linda Crampton is a writer and former teacher with a first-class honors degree in biology. She writes about the scientific basis of disease.
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 that 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.
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
A triglyceride is a fat molecule. Although too many triglycerides are unhealthy, they are vital molecules. They are normally stored in fat cells (or adipocytes) 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 the ability to lower the triglyceride level.
Health Canada agrees with the claim that DHA (and EPA) lowers triglycerides, but states certain requirements in order for product packages to make this claim. The requirements are listed in the second reference below. I think it's worth thinking about the stipulations that are listed. They are related to the quantity of omega-3 oils in a product, added salt, and the amount of mercury in fish. It's best to choose fish that doesn't contain much mercury. The substance can be harmful for us.
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.
The chemical 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.
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. The hippocampus plays an important role in memory. The researchers also found that the cells in the hippocampus could communicate with each other better when more DHA was present.
It's important to note that discoveries in lab animals may or may not apply to humans. The observations described above might explain why DHA seems to improve memory, however. 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.
Surveys of humans can provide interesting and significant information. Information gained from a survey is generally not considered to be as accurate as that obtained from a clinical trial, however. A popular saying in science that is related to survey results is "Correlation does not imply causation."
Potential 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.
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 has 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.
Sources of DHA
Oily Fish and Krill
The best way to get DHA is in the diet. Oily fish such as wild salmon, some types of 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, as mentioned earlier. Mercury is an ocean pollutant and is toxic to humans. It affects multiple systems in our body, including our nervous system. Pregnant and breastfeeding women and ones with young children need to be especially careful in their choice of fish. The FDA document in the "References" section below offers some advice. Another point to consider is that the fishing industry used to harvest the animals should 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.
An Omega-3 Poll
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 the nutrient is definitely worthwhile.
- Scientific opinion about DHA health claims from the European Food Safety Authority, or EFSA. (This report is a PDF file at the Wiley Online Library.)
- The Canadian government's opinion about the claim that DHA lowers triglycerides.
- DHA increases synaptic transmission in the mouse hippocampus and may improve memory from Applied Physiology, Nutrition, and Metabolism (Abstract)
- Docosahexaenoic acid and liver disease from Oregon State University
- DHA and suicide risk in military personnel from the NIH (National Institutes of Health)
- Information about the mercury level in fish from the FDA (Food and Drug Administration)
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
© 2013 Linda Crampton
Linda Crampton (author) from British Columbia, Canada on February 17, 2013:
Hi, Peggy. Yes, "brain food" is a good name for fish that contain DHA! Thank you for the visit and the comment.
Peggy Woods from Houston, Texas on February 17, 2013:
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." :)
Linda Crampton (author) from British Columbia, Canada on February 15, 2013:
Thanks for the visit, Dianna. I like sardines, too, as well as salmon. It is good to know that they are healthy foods.
Dianna Mendez on February 15, 2013:
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.
Linda Crampton (author) from British Columbia, Canada on February 10, 2013:
It's great when someone enjoys a food that's good for them! Thanks for the comment, mylindaelliot.
mylindaelliott from Louisiana on February 10, 2013:
Those are all good reasons to enjoy food that I already like.
Linda Crampton (author) from British Columbia, Canada on February 09, 2013:
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!
Kathi Mirto from Fennville on February 09, 2013:
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)
Linda Crampton (author) from British Columbia, Canada on February 09, 2013:
Thank you, JCielo. I appreciate your comment very much! Your advice about choosing an omega-3 oil supplement is excellent.
JCielo from England on February 09, 2013:
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!
Linda Crampton (author) from British Columbia, Canada on February 08, 2013:
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.
Deb Hirt from Stillwater, OK on February 08, 2013:
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!
Linda Crampton (author) from British Columbia, Canada on February 08, 2013:
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.
Leah Lefler from Western New York on February 08, 2013:
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!
Linda Crampton (author) from British Columbia, Canada on February 07, 2013:
They are tricky words - they don't exactly roll off the tongue! Thank you very much for the visit and the comment, drbj.
drbj and sherry from south Florida on February 07, 2013:
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.