20 January 2015 Fish Oil: Fish tale or not?

It all started in the 1970s with observational studies of the Greenland Eskimos (1). Danish Researchers speculated that the Eskimo’s diet, high in oily, cold-water fish, had a protective effect against heart disease. Since then, more than 5,000 studies have been published examining the beneficial effects of omega-3 fatty acids. The original Eskimo study has since been criticized for its lack of validity, and the thousands of studies since have produced conflicting results about the effects of fish oil on many different aspects of health.

So, what is so special about fish oil anyway? Fish oil, unlike fat from beef, pork, poultry or milk, contains high amounts of polyunsaturated fats called omega-3 fatty acids. The two main types of omega-3s are eicosapentaenoic acid (EPA) and docosaheaenoic acid (DHA) (2). The body cannot make omega-3s, and they are not plentiful in the typical Western diet unless you seek them out. Most experts think that EPA and DHA have different effects on the body than the plant-based omega-3 fatty acid, alpha-linolenic acid, found in foods such as flaxseed, walnuts, canola oil, soybeans and tofu. These plant foods are extremely nutrient-rich for other reasons though.

Omega-3s from fish oil have anti-inflammatory effects. They thin the blood, may control blood pressure and may even increase tear secretions to reduce dry eye syndrome. DHA is thought to play an important role in brain function and some researchers think it might help prevent some forms of cancer. The list of all the areas of the body thought to be influenced by omega-3 fatty acids are too numerous to mention in this blog(3).

Omega-3s have been extensively studied for effects on many areas of health, including high cholesterol and high triglycerides (blood fats), high blood pressure, infant development, kidney health and dementia. The strongest evidence, to date, in favor of the benefit of (high-dose) omega-3s is its potential to lower severely high triglycerides(4). Controversy does exist, however, over the degree of protection from omega-3s in preventing heart disease. Current clinical trials (the gold standard in health research) are underway to sort through the questions about omegs-3s and heart health.

The American Heart Association (AHA) recommends eating fish, especially fatty fish, twice a week(5). The recommended serving is 3-4 oz cooked or ¾ cup flaked fish. The AHA also recommends 1,000 mg omega 3s per day for those with established heart disease. Most health experts recommend individuals get 250-500 mg of omega 3s a day.

How can you apply this advice? Darker, oily fish has the highest level of omega-3s. Examples include herring, salmon, mackerel, tuna, sardines, rainbow trout and anchovies. Leaner fish is still an excellent protein choice, just low in omega-3s. A 3-oz serving of sockeye salmon has about 1,400 mg omega-3 fatty acids, while a 3-oz serving of canned tuna has about 1,000 mg omega-3s. If you had one serving of each per week, it would average out to 343 mg omega-3s per day, the advised amount for a healthy individual. If you are not a fish eater, a fish oil supplement may be a reasonable alternative.

As with most nutrients, more is not always better. Unless you are under medical supervision for a health condition, higher doses of 3 or more grams of omega-3s per day are not advised as this amount may cause adverse side effects. At high doses, risk of stroke, excessive bleeding, autoimmune effects and contaminant toxicity could be a risk.

References:

  1. http://www.ncbi.nlm.nih.gov/pubmed/78322?dopt=Abstract
  2. http://ods.od.nih.gov/factsheets/Omega3FattyAcidsandHealth-HealthProfessional/
  3. http://www.nlm.nih.gov/medlineplus/druginfo/natural/993.html
  4. http://naturaldatabase.therapeuticresearch.com
  5. http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/HealthyDietGoals/Fish-and-Omega-3-Fatty-Acids_UCM_303248_Article.jsp

Brenda Braslow, MS, RD, CDE

Brenda is a registered dietitian and certified diabetes educator in Denver,

Colorado who specializes in diabetes prevention and health enhancement.

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Disclaimer: The information provided here does not constitute medical advice. If you are seeking medical advice, please visit your healthcare provider or medical professional.

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Nutrients/Fats Other Health Issues/Cardiovascular Disease

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