New study on dietary fish oil…

The title of a new study says it all: “Dietary Fish Oil Alters T Lymphocyte Cell Populations and Exacerbates Disease in a Mouse Model of Inflammatory Colitis” (see abstract: I was concerned when I first read of this study because I take two grams of fish oil per day, and I certainly do not want to take anything that might hurt me…

So I asked a friend (thanks!) to get the full study for me. I wanted to read more details about doses, the type of fish oil administered to this unfortunate group of mice and any other pertinent information. Let’s see…In a nutshell, four weeks after being infected with Helicobacter hepaticus (which gave them mild colitis and increased their risk of developing colon cancer…), mice consuming relatively high doses of dietary fish oil, as we will see in a second, were worse off than those in the control group.

Well, I have to admit that my first draft of this post was jam-packed with technical details about colon cancer, colitis, IBD (=irritable bowel disease), the mice, their diets and whatnot. But, after getting to the Discussion part of the study, I had second thoughts about going overboard with too many details. After all, what we really need to know can be found in the final paragraph, as follows:

Investigations regarding FO supplementation in human IBD have used FO doses ranging between 500 mg/d and 7 g/d. Our diets mimicked 1 g/d (0.75%), 3 g/d (2.25%), 5 g/d (3.75%), and 8 g/d (6.00%) DFO when calculated as a component of a 2,000 kcal human diet. We observed inflammatory and dysplastic changes at the 3, 5, and 8 g equivalent. The most dramatic increase was observed at the 8 g/d dose. Currently, efforts are under way to establish dietary reference intakes for EPA and DHA due to substantial evidence supporting beneficial effects of FO consumption in the prevention of common diseases such as coronary artery disease and cognitive decline. Consumer intakes of DHA and EPA continue to increase with growing FO supplement consumption and addition of n-3 PUFAs to foods (i.e., functional food). Studies from our group and others’ advocate establishing a tolerable upper limit for FO consumption to protect certain immunocompromised sectors of the population who may be at risk for pathogen-associated enteric inflammation and gastrointestinal cancers.

Now, the mice that developed inflammatory problems belonged to the groups that had a high daily intake of fish oil–the human equivalent of 3 to 8 grams/day. The more they took, the worse off they were. Another point: as we read the abstract/study, let’s not forget that these mice were not healthy little things. No, they had been infected with a nasty virus that can lead to the development of colon cancer…

Two more considerations (apart from the obvious one that, as far as I know!, I am not a…mouse! 😉 ): 1. I have never taken more than 2 grams of fish oil per day; 2. I live in Italy, where foods are not (yet!) fortified with dietary PUFAs or even vitamins. Therefore, it appears that my daily intake of fish oil is perfectly safe, especially since I do not suffer from colitis or IBD…

As always, though, it is best to be cautious. And so I will continue to take two grams of fish oil per day…but no more than that.


  1. Well, now I feel a bit better about fish oil caps. I will probably keep up the 2 g/day as well. My HDL is amazing; want to keep it that way!

  2. I was also surprised and shocked with the study….. but there are so many studies in which omega 3 reduce cancer rates, and delay progression.

    They also say that probably EPA have a more guilty posture than DHA.

    I also don’t take many. I take 500 mg of DHA and 380 of EPA.

    Thanks margaret

  3. Hi Margaret,

    I’m a little confused by the abstract for that study. At first glance it sounds like they are just testing fish oil, but a little further in it sounds like they are testing fish oil that is enriched with extra DHA…..not exactly something that consumers are likely to be able to go out and buy??? I have always understood that part of the anti-inflammatory effect of omega 3’s (EPA + DHA) is contingent upon a specific balance between the two that is approximatelly 2 parts EPA to 1 part DHA…..I do not remember the exact ratio, but I think it was something like that. If that is the case, wouldn’t the altered or DHA enriched fish oil actually have a different anti-inflammatory profile if at all?
    Does the complete study shed any light on this issue or name the exact ratio of EPA to DHA in the tested fish oil?
    I am interested/concerned because I consume about 4 grams of omega 3 per day from 7.2 grams of fish oil!

    Thank You.


  4. I am sooo glad you brought up that point, Art. In my first draft, in fact, I had a note about the DHA/EPA ratio. When I decided to alter/shorten my draft, though, I didn’t include that note (my brain is clogged with a cold, still…).
    Here is the relevant section from the study: “DFO
    contained 540 mg/g DHA and 50 mg/g EPA.” Huge difference!
    Like you, I recalled that my fish oil capsules contain more EPA than DHA. I double-checked and found that each capsule contains 800 mg EPA vs 400 mg DHA.
    What that means, exactly, is beyond my powers right now.
    Hmmm, it might be worth writing to the authors for clarification.

  5. Thank you for the reply, Margaret!

    Yes, that epa/dha ratio is not likely to be easilly found in the retail sector and it begs the question, is using the term, “fish oil”, a bit misleading in this study?
    Is it really giving an accurate expectation of what would happen if you were to take typical commercially available fish oil supplements? I’m thinking probably not.
    From studies I have read previously, 4 grams of omega 3’s (epa + dha) has shown anti-inflammatory results , however, those fish oil supplements were typically closer to the 2 to 1 epa to dha ratio. I am curious though, why this unusual ratio was used for the study.


Leave a Reply

Your email address will not be published. Required fields are marked *