DHA and food

23 April 2018

The expression ‘you are what you eat’ applies to the entire body, including the brain. In the brain, what you eat influences the production of neurotransmitters, the chemicals that help the brain function. A diet that is low in protein, mineral nutrients, or vitamins may result in an imbalance of neurotransmitters which can impact how the brain functions.[1] DHA, an omega-3 fatty acid, is the most abundant fatty acid in the brain and is necessary for the development of neurotransmitters. [2]

Although our body can make most of the types of fats it needs from other fats, this isn’t the case for omega-3 fatty acids. Since the body cannot make omega-3 fatty acids from scratch, we need to get our omega-3 from food. Foods high in omega-3 include fish, vegetable oils, nuts (especially walnuts), flax seeds, flaxseed oil, and leafy vegetables.[3] Throughout our entire lives, we need various types of food sources that are rich in DHA to maintain healthy brain development and maintenance.

Pregnant mom, baby in utero, breastfed babies, and DHA

Many pregnant women likely do not get enough omega-3 fatty acids in their diet. A survey found that half of pregnant American women ate fewer than two ounces a week of foods rich in DHA, which is not nearly enough for themselves and their growing baby. [4]  Sometimes pregnant women are cautious and hesitant about eating fish and seafood because they want to know more about mercury levels, as too much mercury can be potentially harmful to an unborn baby. [5]

When it comes to exclusively breastfed babies, their nutrition depends on what the mother can provide.  Since most mothers do not consume a large enough quantity of omega-3 rich products, they often do not have enough in their own system to pass on to their infant.[6]

The FDA in the United States recommends two to three servings of lower-mercury fish per week, or eight to 12 ounces for pregnant women, with 12 ounces per week being advised as the maximum amount.[5]

Adults and DHA

Only 19 per cent of American adults consume the recommended two servings of fish each week.[7] DHA supplements can help in these situations.[8] Canadians are also advised to eat at least two servings (of 75 grams each) of fish a week.[9]

The risks of mercury exposure from fish and seafood

Mercury can cause damage to the brain and nervous system if a person eats too much food containing traces of it over time.[9] Unfortunately, most fish contain at least some traces of mercury.[9]

Growing infants and young children are the ones who are at greatest risk from mercury exposure. It is important that pregnant and breastfeeding women, women who may become pregnant, and parents of young children are educated about the types of fish that have the lowest levels of mercury, which can be eaten more often, and fish which should be eaten less often due to their higher levels of mercury.[9]

Canned tuna and canned light tuna are good options because the fish used in canned tuna and canned light tuna are typically younger and smaller and contain significantly less mercury than fresh or frozen tuna.[9]

Other types of fish and shellfish that contain higher levels of DHA and are also low in mercury include: anchovy, capelin, char, hake, herring, Atlantic mackerel, mullet, pollock (Boston bluefish), salmon, smelt, rainbow trout, lake whitefish, blue crab, shrimp, clam, mussel, oyster, catfish, pickerel, sardine, sole, and tilapia.[9], [10]

However, large amounts of canned albacore tuna, also known as canned white tuna, may contain higher levels of mercury than is considered acceptable. Other fish which may contain higher levels of mercury are often predatory fish, which eat other fish and as such, end up ingesting and accumulating the mercury from those fish.  These fish should be eaten less often; fresh/frozen tuna, shark, swordfish, marlin, orange roughy, escolar, king mackerel, and tilefish [9], [10]

Supplements containing DHA is a safe way of supplementing the diet of a pregnant or breastfeeding woman, as well as children themselves, without the risk of mercury.

  1. [1] Wendolowicz A, Stefanska E, Ostrowska L, Influence of selected dietary components on the functioning of the human nervous system. Rocz Panstw Zakl Hig., 2018;69(1):15-21.
  2. [2] Hee-Yong Kim. Novel Metabolism of Docosahexaenoic Acid in Neural Cells. The Journal of Biological Chemistry. June 29 2007. 18661-18665. 
  3. [3] Harvard T.H. Chan School of Public Health. Omega-3 Fatty Acids: An Essential Contribution. 2017. https://www.hsph.harvard.edu/nutritionsource/omega-3-fats/
  4. [4] U.S. Food and Drug Administration. FDA and EPA issue final fish consumption advice. May 31 2017. https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm537362.htm
  5. [5] James A Greenberg, Stacey J Bell, Wendy Van Ausdal. Omega-3 Fatty Acid Supplementation During Pregnancy. Rev Obstet Gynecol. 2008 Fall; 1(4): 162-169. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2621042/
  6. [6] Erick M. Breast milk is conditionally perfect. Med Hypotheses. 2018 Feb;111:82-89. Epub 2017 Dec 14.
  7. [7] Smith KM, Sahyoun NR. Fish consumption: recommendations versus advisories, can they be reconciled? Nutr Rev. 2005 Feb; 63(2):39-46.
  8. [8] James A Greenberg, Stacey J Bell, Wendy Van Ausdal. Omega-3 Fatty Acid Supplementation During Pregnancy. Rev Obstet Gynecol. 2008 Fall; 1(4): 162-169. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2621042/
  9. [9] Health Canada.  Mercury in Fish. 02/3/2017. https://www.canada.ca/en/health-canada/services/food-nutrition/food-safety/chemical-contaminants/environmental-contaminants/mercury/mercury-fish.html
  10. [10] FDA U.S. Food and Drug Administration. Eating Fish: What Pregnant Women and Parents Should Know. 11/29/2017.  https://www.fda.gov/Food/ResourcesForYou/Consumers/ucm393070.htm
Tags: brain, DHA, oily fish, omega-3, omega-3 fatty acids, recommendations, seafood


Natalie Bourré

Natalie works as a consultant for various medical organizations and pharmaceutical companies. Her goal is to help them communicate accurate medical information in patient-friendly language via traditional and digital marketing methods.

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