Omega-3 MUST be from fish oil

Despite my rants in this blog and elsewhere, at least once a day I'll have a patient say, "I cut back (or eliminated) my fish oil because I get my omega-3s from _______ (insert your choice of flaxseed oil, walnuts, yogurt, mayonnaise, bread, etc.)."

(See prior Heart Scan Blog post: Everything has omega-3.)

When I point out to them that the "omega-3s" in these products are not the same as the EPA and DHA from fish oil, they invariably declare, "But it says so here on the label: 'Contains 200 mg of omega-3 fatty acids'!"

Apparently, some of my colleagues have even endorsed this concept of replacing the omega-3s from fish oil with these "alternatives."

It's simply not true. The linolenic acid that is being labeled as omega-3, while it may indeed provide health benefits of its own, cannot replace the EPA and DHA that fish oil provides.

The most graphic example of the differences between the two classes of oils is in people with a condition called familial hypertriglyceridemia. People with this condition have triglyceride levels of 400, 600, even thousands of mg/dl--very high. Fish oil, usually providing EPA and DHA doses of 1800 mg per day and higher, reduce triglycerides dramatically. A person with a starting triglyceride level of, say, 900 mg/dl, may take 2400 mg of EPA and DHA from fish oil and triglycerides plummet to 150 mg/dl. This person then decides to replace fish oil with a linolenic acid source like flaxseed oil. Triglycerides? 900 mg/dl--no effect whatsoever.

Familial hypertriglyceridemia represents an exagerrated example of the differences between the two oils. Even if you don't have this genetic condition, the differences between the oils still apply.

EPA and DHA are activators of the enzyme, lipoprotein lipase, that accelerates clearance of triglycerides from the blood. Linolenic acid from flaxseed oil, walnuts, and other food sources does not. EPA and DHA block after-eating (post-prandial) accumulation of food by-products that can contribute to coronary and carotid plaque. Linolenic acid does not. EPA and DHA block platelets, reduce fibrinogen, and exert other healthy blood clot-inhibiting effects. Linolenic does not.

The 11,000-participant GISSI-Prevenzione Trial that showed 28% reduction in heart attack, 45% reduction in cardiovascular death with omega-3s used . . . fish oil.

The 18,000 participant JELIS trial that showed 19% reduction in cardiovascular events when omega-3s were added to statin therapy used . . . fish oil. (Actually, in JELIS, they used only EPA wtihout DHA.)

Linolenic acid is not a waste, however. It may exert anti-inflammatory benefits of its own, for instance. But it exerts none of the triglyceride-modifying effects of EPA or DHA.

EPA and DHA from fish oil and linolenic acid from foods each provide benefits in their own way. Ideally, you include both forms of oils--fish oil and linolenic acid sources--in your daily diet and obtain full benefit from each separate class. But they are not interchangeable.

Copyright 2008 William Davis, MD

Comments (14) -

  • Michael

    3/7/2008 2:59:00 AM |

    Anyone have any experience using krill oil, and how does it compare to fish oil?

    As for other forms of omega-3s, isn't flax considered dangerous for men, due to ALA content? There are conflicting studies, but I recall at least one that said ALA caused a rise in the rate or prostate cancer.

  • Zubin

    3/7/2008 3:31:00 AM |

    Is there any way for a vegetarian to replace fish oil and get the same benefits?

  • Missbossy

    3/7/2008 5:01:00 AM |

    I am definitely down with the fact that Fish Oil is vastly superior to Flax Oil. I've seen quite a few people touting flax oil lately so I'm glad you put that to bed.

    Question: You mention recommended doses of EPA and DHA for those with elevated triglycerides. Can you offer any guidance for supplement levels when triglycerides aren't an issue? IE a level for good preventative nutrition? I've looked around and recommendations are all over the shop.


  • Anonymous

    3/7/2008 12:53:00 PM |

    I've read a few other articles about the differences between fish oil omega-3s and other sources, but this article spells it out very clearly about how those differences apply directly to heart disease. I'll be printing this one for my family. Thanks!


  • Anonymous

    3/7/2008 2:11:00 PM |

    Vegetarian DHA is available. It is cultured from algae. That's where the fish get. EPA may be available now too.

  • Anonymous

    3/7/2008 3:52:00 PM |


    There are vegetarian DHA/EPA supplements made from algae.

  • Liss

    3/8/2008 12:09:00 AM |

    Zubin, when I followed a vegetarian diet I was able to find DHA supplements derived from algae, but EPA is harder to come by.  V-Pure is the only one I found that contained both EPA and DHA.  The capsules are costly, but might be a good option for you if you aren't comfortable taking krill or fish oil.

  • Zubin

    3/9/2008 2:06:00 PM |

    Thanks all, I will look into the algae supplements!

  • Anonymous

    5/12/2008 1:03:00 PM |

    As a newcomer to your blog please forgive me if this topic has been brought up before.
    There is a scathing attack in an article by Ray Peat,a noted Biology professor, on the damaging effects of fish oil.
    A few people have stopped taking fish oil after reading the article.
    Can you please comment?

  • Anonymous

    7/8/2008 4:05:00 AM |
    A Reply to Ray Peat
    on Essential Fatty Acid Deficiency

    By Mary G. Enig, PhD

    Ray Peat, PhD, is an influential health writer who claims that there is no such thing as essential fatty acid (EFA) deficiency. According to Peat, the body can make its own EFAs; furthermore, he claims that EFAs in the body become rancid and therefore cause cancer.

    Unfortunately, Peat does not understand the use of EFA by the human body. He is trained in hormone therapy and his training in fats and oils has been limited to misinformation as far as the polyunsaturated fats and oils are concerned.

    Research on EFAs is voluminous and consistent: EFAs are types of fatty acids that the body cannot make, but must obtain from food. We do not make them because they exist in virtually all foods, and the body needs them only in small amounts. The body does make saturated and monounsaturated fatty acids because it needs these in large amounts and cannot count on getting all it needs from food.

    There are two types of EFAs, those of the omega-6 family and those of the omega-3 family. The basic omega-6 fatty acid is called linoleic acid and it contains two double bonds. It is found in virtually all foods, but especially in nuts and seeds. The basic omega-3 fatty acid is called linolenic acid and it contains three double bonds. It is found in some grains (such as wheat) and nuts (such as walnuts) as well as in eggs, organ meats and fish if these animals are raised naturally, and in green vegetables if the plants are raised organically.

    Essential fatty acids have two principal roles. The first is as a constituent of the cell membrane. Each cell in the body is surrounded by a membrane composed of billions of fatty acids. About half of these fatty acids are saturated or monounsaturated to provide stability to the membrane. The other half are polyunsaturated, mostly EFAs , which provide flexibility and participate in a number of biochemical processes. The other vital role for EFAs is as a precursor for prostaglandins or local tissue hormones, which control different physiological functions including inflammation and blood clotting.

    Scientists have induced EFA deficiency in animals by feeding them fully hydrogenated coconut oil as their only fat. (Full hydrogenation gets rid of all the EFAs; coconut oil is used because it is the only fat that can be fully hydrogenated and still be soft enough to eat.) The animals developed dry coats and skin and slowly declined in health, dying prematurely. (Interestingly, representatives of the vegetable oil industry blame the health problems on coconut oil, not on fatty acid deficiency!)

    In a situation of fatty acid deficiency, the body tries to compensate by producing a fatty acid called Mead acid out of the monounsaturated oleic acid. It is a 20-carbon fatty acid with three double bonds named after James Mead, a lipids researcher at the University of California at Los Angeles who first identified it. An elevated level of Mead acid in the body is a marker of EFA deficiency.

    According to Peat, elevated levels of Mead acid constitute proof that your body can make EFAs. However, the Mead acid acts as a "filler" fatty acid that cannot serve the functions that the original EFA are needed for. Peat claims that Mead acid has a full spectrum of protective anti-inflammatory effects; however, the body cannot convert Mead acid into the elongated fatty acids that the body needs for making the various anti-inflammatory prostaglandins.

    Peat also asserts that polyunsaturated fatty acids become rancid in our bodies. This is not true; the polyunsaturated fatty acids in our cell membranes go through different stages of controlled oxidation. To say that these fatty acids become "rancid" is misleading. Of course, EFAs can become rancid through high temperature processing and it is not healthy to consume these types of fats. But the EFAs that we take in through fresh, unprocessed food are not rancid and do not become rancid in the body. In small amounts, they are essential for good health. In large amounts, they can pose health problems which is why we need to avoid all the commercial vegetable oils containing high levels of polyunsaturates.

    Peat’s reasoning has led him to claim that cod liver oil causes cancer because cod liver oil contains polyunsaturated fatty acids. Actually, the main fatty acid in cod liver oil is a monounsaturated fatty acid. The two main polyunsaturated fatty acids in cod liver oil are the elongated omega-3 fatty acids called EPA and DHA, which play many vital roles in the body and actually can help protect against cancer. Furthermore, cod liver oil is our best dietary source of vitamins A and D, which also protect us against cancer.

    Actually, Peat’s argument that polyunsaturated fatty acids become harmful in the body and hence cause cancer simply does not make sense. It is impossible to avoid polyunsaturated fatty acids because they are in all foods.

    EFAs are, however, harmful in large amounts and the many research papers cited by Peat showing immune problems, increased cancer and premature aging from feeding of polyunsaturates simply corroborate this fact. But Peat has taken studies indicating that large amounts of EFAs are bad for us (a now well-established fact) and used them to argue that we don’t need any at all.

    Finally, it should be stressed that certain components of the diet actually reduce (but do not eliminate) our requirements for EFAs. The main one is saturated fatty acids which help us conserve EFAs and put them in the tissues where they belong. Some studies indicate that vitamin B6 can ameliorate the problems caused by EFA deficiency, possibly by helping us use them more efficiently.

    About the Author
    Mary G. Enig, PhDMary G. Enig, PhD is an expert of international renown in the field of lipid biochemistry. She has headed a number of studies on the content and effects of trans fatty acids in America and Israel, and has successfully challenged government assertions that dietary animal fat causes cancer and heart disease. Recent scientific and media attention on the possible adverse health effects of trans fatty acids has brought increased attention to her work. She is a licensed nutritionist, certified by the Certification Board for Nutrition Specialists, a qualified expert witness, nutrition consultant to individuals, industry and state and federal governments, contributing editor to a number of scientific publications, Fellow of the American College of Nutrition and President of the Maryland Nutritionists Association. She is the author of over 60 technical papers and presentations, as well as a popular lecturer. Dr. Enig is currently working on the exploratory development of an adjunct therapy for AIDS using complete medium chain saturated fatty acids from whole foods. She is Vice-President of the Weston A Price Foundation and Scientific Editor of Wise Traditions as well as the author of Know Your Fats: The Complete Primer for Understanding the Nutrition of Fats, Oils, and Cholesterol, Bethesda Press, May 2000. She is the mother of three healthy children brought up on whole foods including butter, cream, eggs and meat.


    In the Winter 2004 "Know Your Fats" column we stated that Siberian pinenut oil was a good source of gamma-linolenic acid (GLA). This was indicated from fatty acid analyses performed in Siberia. We have since performed further tests on the oil and found that it does not contain significant amounts of GLA but rather a fatty acid called pinoleic acid, an 18-carbon fatty acid with three double bonds but with the first double bond on the fifth carbon, not the sixth, as in GLA. We are sorry for any inconvenience this may have caused.

  • Arlie

    6/5/2009 4:26:30 PM |

    I'm a 57 year old grandma and have been vegan for over 6 years. I've run 3 marathons since turning 50, but took at 18 month hiatus to care for a grandson.  I was slowly trying to get back into running by starting out with 20 min. jogs and 3 minutes of jumping rope. Last October I developed painful tendinitis in my M.D. encouraged me to try O.T.C. painkillers (aspirin, acetaminophen, and ibuprofen) and take glucosamine all to no avail...he sent me to a physical therapist who gave me a few exercises said I shouldn't run at all, ever...that he quit running at age 30 and advises walking only. At that point my doctor wanted to prescribe some NSAID and give me a 2nd prescription for something that would allow my stomach to handle the prescription NSAID.   Without my M.D.'s recommendation I went to an acupuncturist for 3 luck there.  Then a few months ago, again without my M.D.'s referral, I went to a chiropractor.  Since I was vegan, he prescribed flax oil, which seemed to help only a little, although the chiropractor said he really thought I would benefit the most from fish liver oil. Yesterday, in desperation, I took fish oil and felt much better.  I'm not pain free yet...but the improvement was quite dramatic.  I'll have to see how it goes.  I was vegan for personal, ethical reasons as opposed to health even though this is a bit of a disappointment for me and my veganism...I think I will continue to use the fish oil and see if I benefit further.  By the way I had been taking vegan DHA for years from either "Omega Zen" or "Deva". Many, many years ago I heard that the playwright George Bernard Shaw had to take liver for a B-12 deficiency.  As the story goes someone said to him, "Is that liver you're eating...I thought you were a vegetarian."  Shaw replied "I am, this is my medicine."

  • Anonymous

    2/15/2010 9:11:25 PM |

    Ah, This is exactly what I was looking for! Clears up
    a few misnomers I've read

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  • moseley2010

    12/8/2010 4:40:26 PM |

    I have heard about acai berries and acai berry supplements containing sufficient Omega 3. I found out about this while I was looking for great alternatives for kids. Because for sure, they don't like fish oil supplements as they are huge and smelly, but I also believe they need the Omega 3 and all the good it brings. I found out about acai berry powder with Omega 3. I admit I am almost convinced.