When It Comes to Fish Oil, More Is Not Better | Chris Kresser
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When It Comes to Fish Oil, More Is Not Better

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Update: I now recommend Extra Virgin Cod Liver Oil from Rosita as my preferred cod liver oil product. For more information, read this article. You can purchase EVCLO here.

Article summary

  • The benefits of fish oil supplementation have been grossly overstated
  • Most of the studies showing fish oil benefits are short-term, lasting less than one year
  • The only fish oil study lasting more than four years showed an increase in heart disease and sudden death
  • Fish oil is highly unstable and vulnerable to oxidative damage
  • There’s no evidence that healthy people benefit from fish oil supplementation
  • Taking several grams of fish oil per day may be hazardous to your health

A new study was recently published showing that 3g/d of fish oil in patients with metabolic syndrome increased LDL levels and insulin resistance.

Unfortunately, I don’t read Portuguese so I can’t review the full-text. But this study isn’t alone in highlighting the potential risks of high-dose fish oil supplementation. Chris Masterjohn’s latest article on essential fatty acids, Precious yet Perilous, makes a compelling argument that fish oil supplementation – especially over the long-term – is not only not beneficial, but may be harmful.

This may come as a surprise to you, with all of the current media hoopla about the benefits of fish oil supplementation. Yet the vast majority of the studies done that have shown a benefit have been short-term, lasting less than one year. The only trial lasting more than four years, the DART 2 trial, showed that fish oil capsules actually increase the risk of heart disease and sudden death.

A 2004 Cochrane meta-analysis of trials lasting longer than six months suggests that the cardiovascular benefits of fish oil have been dramatically over-stated. They analyzed 79 trials overall, and pooled data from 48 trials that met their criteria. The only effect that could be distinguished from chance was a reduced risk of heart failure. Fish oil provided no reduction in total or cardiovascular mortality.

Too much fish oil can wreak havoc in your body

Omega-3 fatty acids are highly vulnerable to oxidative damage. When fat particles oxidize, they break down into smaller compounds, like malondialdehyde (MDA), that are dangerous because they damage proteins, DNA, and other important cellular structures.

A study by Mata et al demonstrated that oxidative damage increases as intake of omega-3 fat increases. The results of this study were summarized in the Perfect Health Diet, by Paul and Shou-Ching Jaminet:

oxidativedamage

Notice the clear increase in TBARS (a measure of oxidative damage of the LDL particle) with omega-3 fat. It’s important to note that this was only a 5-week trial. If it had gone on for longer than that, it’s likely the oxidative damage caused by omega-3 fats would have been even worse. This isn’t surprising if you understand the chemical composition of fats. Polyunsaturated fats (PUFA) are highly vulnerable to oxidative damage because they’re the only fatty acids that have two or more double bonds, and it’s the carbon that lies between the double bonds that is vulnerable to oxidation (as shown in the figure below):

diagram of chemical structure of EPA

Another thing worth noting, if you haven’t already, is that intake of saturated and monounsaturated fats does not increase oxidative damage by a significant amount. This is illustrated in both the table and the diagram above: saturated fats have no double bonds, which means they are well protected against oxidation. MUFA is slightly more vulnerable, since it does have one double bond, but not nearly as much as PUFA which has several double-bonds.

A randomized, double blind, placebo-controlled trial likewise showed that 6 grams per day of fish oil increased lipid peroxides and MDA in healthy men, regardless of whether they were supplemented with 900 IU of vitamin E. And consumption of fresh, non-oxidized DHA and EPA has been shown to increase markers of oxidative stress in rats.

Fish oil not as beneficial as commonly believed

To be fair, at least one review suggests that fish oil supplementation is beneficial in the short and even intermediate term. A recent meta-analysis of 11 trials lasting more than one year found that fish oil reduced the relative risk of cardiovascular death by 13 percent and the relative risk of death from any cause by 8 percent.

But the effect seen in this review was mostly due to the GISSI and DART-1 trials. They found that fish oil may prevent arrhythmia in patients with chronic heart failure and patients who have recently survived a heart attack.

However, there is no evidence that people other than those with arrhythmia and chronic heart failure benefit from taking fish oil or that doses higher than one gram of omega-3 fatty acids per day provide any benefit over smaller doses. And then there’s the rather disturbing result of the DART-2 trial, the only fish oil study lasting more than four years, showing an increase in heart disease and sudden death.

It’s logical to assume the effects of oxidative damage would take a while to manifest, and would increase as time goes on. That’s likely the reason we see some benefit in short- and intermediate-term studies (as n-3 displace n-6 in the tissues), but a declining and even opposite effect in the longer-term DART-2 trial (as increased total PUFA intake causes more oxidative damage).

The danger of reductionist thinking in nutritional research

The current fish oil craze highlights the danger of isolated nutrient studies, which unfortunately is the focus of nutritional research today. Kuipers et al. eloquently described the risks of this approach in a recent paper:

The fish oil fatty acids EPA and DHA (and their derivatives), vitamin D (1,25-dihydroxyvitamin D) and vitamin A (retinoic acid) are examples of nutrients that act in concert, while each of these has multiple actions(7,8).

Consequently, the criteria for establishing optimum nutrient intakes via randomised controlled trials (RCT) with single nutrients at a given dose and with a single end point have serious limitations. They are usually based upon poorly researched dose–response relationships, and typically ignore many possible nutrient interactions and metabolic interrelationships.

For instance, the adequate intake of linoleic acid (LA) to prevent LA deficiency depends on the concurrent intakes of α-linolenic acid (ALA), γ-LA and arachidonic acid (AA). Consequently, the nutritional balance on which our genome evolved is virtually impossible to determine using the reigning paradigm of ‘evidence-based medicine’ with RCT.

Interest in fish oil supplementation started with observations that the Inuit had almost no heart disease. It was assumed their high intake of marine oils produced this benefit. While this may be true, at least in part, what was overlooked is that the Inuit don’t consume marine oils in isolation. They eat them as part of a whole-food diet that also includes other nutrients which may help prevent the oxidative damage that otherwise occurs with such a high intake of fragile, n-3 PUFA.

It’s also important to note that there are many other traditional peoples, such as the Masai, the Tokelau, and the Kitavans, that are virtually free of heart disease but do not consume high amounts of marine oils. What these diets all share in common is not a large intake of omega-3 fats, but instead a complete absence of modern, refined foods.

Eat fish, not fish oil – cod liver oil excepted

That is why the best approach is to dramatically reduce intake of omega-6 fat, found in industrial seed oils and processed and refined foods, and then eat a nutrient-dense, whole-foods based diet that includes fatty fish, shellfish and organ meats. This mimics our ancestral diet and is the safest and most sane approach to meeting our omega-3 needs – which as Chris Masterjohn points out, are much lower than commonly assumed.

Some may ask why I continue to recommend fermented cod liver oil (FCLO), in light of everything I’ve shared in this article. There are a few reasons. First, I view FCLO as primarily a source of fat-soluble vitamins (A, D, K2 and E) – not EPA and DHA. Second, in the context of a nutrient-dense diet that excludes industrial seed oils and refined sugar, and is adequate in vitamin B6, biotin, calcium, magnesium and arachidonic acid, the risk of oxidative damage that may occur with 1g/d of cod liver oils is outweighed by the benefits of the fat-soluble vitamins.

So I still recommend eating fatty fish a couple times per week, and taking cod liver oil daily, presuming your diet is as I described above. What I don’t endorse is taking several grams per day of fish oil, especially for an extended period of time. Unfortunately this advice is becoming more and more common in the nutrition world.

More is not always better, despite our tendency to believe it is.

Note: As always, I’m open to discussion and dissenting views. But please don’t link to short-term studies on the efficacy of fish oil, because as I’ve explained in this article, it’s the long-term effects that we’re primarily concerned with. I’d be interested in seeing any studies longer than 2 years showing that 1) fish oil benefits extend beyond reducing arrhythmia in patients with chronic heart failure and patients who have recently survived a heart attack, 2) doses higher than 1g/d produce a larger benefit than doses of 1g/d, and (most importantly) 3) doses of >1g/d or higher do not increase the risk of heart disease or death

387 Comments

Join the conversation

  1. Chris,
    Thanks so much for this article. I had suspected this and wince when I hear about young healthy people taking back 15 capsules a day.
    Anecdotally, I switched to Green Pastures FCLO and I have to say it’s had much more of an impact on my health, no idea what’s making the difference as I always thought my diet was nutrient-rich.
    On that point, at this latitude (Ireland), do you really think the 400IU of D in the FCLO is sufficient? I do supplement with an extra 2,000IU D3, and I notice it makes me feel better and increases my resistance to colds. Am I harming my health in the long run doing this?

  2. Jake: thanks for your comment.

    I’m keeping an open mind about this, but your explanation doesn’t account for the increased levels of oxidative damage caused by n-3 intake as measured in the RCTs I mentioned in the article.

    Also, note that the studies do suggest that fish oil benefits patients with arrhythmia and chronic heart failure and/or a recent heart attack.  It’s possible that fish oil may benefit patients with heart disease, but not people that are otherwise healthy.

    FYI, there is an ox-LDL test available now outside of the research setting.  It’s offered by Shiel labs in NY.  Check it out here.  The problem with it is that they don’t have relationships with Quest or Labcorp, so you have to find a way to get blood drawn and then send it yourself.  I’m pretty sure you’ll need a doctor or health care practitioner to place the order, as well.

  3. I think that fish oil consumption is not about eating fish oil, it is about bringing your omega6/omega3 ratio to optimum level.

    My review of this fish oil trials is the dosage used is laughable low. So low that it could not have a positive effect on the omega6/omega3 ratio. That is why you are not seeing positive results in those trials. Also a friend who works in these type of trials says they use the absolute cheapest nutrients to test so the patients are getting crap-that also screws up the results.

    I test that ratio at least every 6 months and the only way I can bring my ratio close to 2 is 4.8 grams of fish oil plus being an absolute Nazi about avoiding omega 6 fats including not eating any nuts other than macadamia nuts.  By doing so I brought my ratio of omega 6 to omega 3 down to 2.7. Because I live in a rural area where good fish is not available, fish oil is my only choice.

    Also William Davis, the famed preventative cardiologist, has been treating thousands of very difficult heart patients with high doses of fish oil (and other things) for over 10 years. All the cardiologists in his region refer their hopeless cases to him.

    In that time he has had no cardiac events in the thousands of patients he has treated for a decade. That means: no stents, no bypass surgeries, no heart attacks and no strokes. He had one person die because he lost 5 close relatives in one year. In addition he is seeing arterial plague progression halted or reversed in most of his patients.

    What is needed is to move the oxLDL test out of the lab and into the hands of the public so this issue can be settled for each person. In the meantime, I have climbed aboard the optimum omega6/omega3 train and I am riding until that test is available. Although I am doing the absolute certainty test by getting a heart scan in the spring.

    • Jake, by comparison to a Paleo period caveman diet, modern diets overdose us with about 30 times as much Omega-6 as we actually need.

      The solution to that problem isn’t to take 30 times as much Omega-3 as we need, to “balance out” the massive overdose of Omega-6. All that would do is give us 60 times as much polyunsaturated fatty acids of both types as what our body needs, and much of that might increase risk of oxidation in LDL.

    • These trials never tell the truth because they use “nutrients” that are lab-made; never found in nature.
      In fact, all these trials using low-quality, isolated, synthetic substances should be banned, because people start commenting and drawing conclusions based on these
      faulty trials, causing confusion.
      The commentators should be more responsible, and check to
      see if the trials are conducted using, high-quality, natural, found-in-nature nutrients, and substances.

  4. Chris: liver is a no go! gag, but I loves me eggs. I’m good on the other nutrients too. It’s also important for folks to remember that too much n-3 is bad too as those fats compete with the same enzymes as n-6, just as an excess of n-6 can inhibit n-3 elongation, excessive n-3 (especially EPA I’ve read) can interfer with AA elongation…that step is there for a reason ya? All goes back to balance.

  5. Doug: consumption of AA-rich foods (liver, egg yolk, etc.) as well as a nutrient-dense diet with adequate levels of B6, biotin, calcium, magnesium and other co-factors will protect against any potential toxicity from EPA.  So yes, I think you’re doing just fine.

  6. i think fish oil can effectively ameliorate an omega 3 deficiency which a lot of people get into thanks to our high veg oil diets otherwise known as SAD.  but if you correct a deficiency and start eating right at the same time, ie, limiting veg oils, eating more meat less carb and so on then i think that is when fish oil becomes counter productive.
    this would explain short term results seen in abbreviated studies right?

  7. Hi

    If 1 tsp (about 4.5g) has ~ 500mg DHA +/- and ~ 300mg DPA +/- and fatty fish can have about 4-5g (total) per 200g/7oz serving, then 1 tsp of cod liver oil daily and 2 servings of fatty fish (assuming 200g per serving, which isn’t a lot) provides on average 2g+ total EPA/DHA. To your point, many healthy, and long-lived peoples do not consume a lot of marine-based n-3. I’ve been taking too much no doubt, and so as not to drive myself crazy with calculations etc. If I get about 1-2g per day, I’m doing well I figure (given I’ve cut out the n-6 sources etc)

    doug

  8. Julie: I still recommend fermented cod liver oil for that, for the reasons I stated at the end of the article.

    kg: possible, but even studies with fresh EPA & DHA have shown that it increases oxidative damage (at least in rats).  This isn’t surprising when we consider the structure of omega-3 polyunsaturated fats.

  9. Chris,
    Is it possible that the fish oil used could taint the results? Considering that there appears to be a lot of pretty bad supplements out there, containing PCBs, it makes me wonder if the actual brand used has an effect on the results. I have been to taking Omegabrite for a while now. Sure hope it hasn’t been doing more harm than good…
     
     

  10. Thank you.  What would you recommend as the best way to maintain a healthy level of vitamin D in the body? (I live in New Hampshire, sun is scarce many months of the year.)   I may have missed this somewhere in other posts.

  11. Another great post on the possible dangers of gulping down high doses of fish oil supps.  I recently had a brief post about this here : http://abundantbrain.com/2010/10/omega3/ and linked to your stuff regarding animal vs. plant sources of EPA/DHA and the fish oil buyer’s guide.  I have long been skeptical of the studies of isolated nutrients not part of a mixed whole foods diet- especially for essential fatty acids which must go through several biochemical conversions and will be affected by the digestive/metabolic environment.  The Kuipers, et al. paper makes some excellent points.
    What does concern me though is the realistic fact that nearly everyone in the U.S. and many other places gets too much omega-6 EVEN those who are cognizant and try to limit the dose.  It’s just so ubiquitous.   I’m curious as to your recommendations for adequate dietary omega-3 for those who do not eat seafood due to allergies or other reasons.

    • Preston, it’s true we are all drowning in Omega-6 PUFAs. It’s also true that Omega-3 and Omega-6 should be closer to a 1:1 ratio. But what I take away from the articles here is that the solution is NOT to massively increase your dose of Omega-3 to compensate for the massive overdose of Omega-6. All that would result in is two massive overdoses of PUFAs, and they are both dangerous when taken above the biological need.

      The real advice here should be get rid of as much polyunsaturated fat as possible from ALL oil-based sources. Ensure baseline needs of Omega-3 from whole foods.

    • Jay, I was trying 500 mg of krill oil as well, but have you opened a jar of that stuff and smelled it? Mine smells really rancid, way beyond just fishy smelling.

      And the point I am starting to takeaway from Chris’ source articles is that we just get too much polyunsatured fat in our diets. It’s being added into every commercial food. It’s in olive oil and most monounsaturated oils. It’s in trace quantities in lots of foods. Our actual biological needs for Omega-3 and Omega-6 are not large and anything above the baseline need appears to do more harm than good.

  12. You are so right, too much PUFA is bad and an omega 6/3 ratio that is or too high or too low is bad. Furthermore do fish oil supplement provide too much EPA in relation to DHA. Just limit your omega 6 intake and eat fish a couple of times per week.

  13. Chris, A big thank you for this article.  I have been seeing hints of this elsewhere and now the details.  I have been concerned about fish oil supplementation for one simple fact — most of the brands contain soy oil.  I know that soy is poison and I am trying to reduce my intake of soy and since it seems to be in ALL refined foods, it is hard.  It seems ridiculous to take something that is supposed to be good for you and then back load it with an extremely harmful oil even if it is a binder.  I have also seen Vitamin D supplements with soy in them.  Very disturbing.

  14. Good article, Chris.  Bill, that’s not true — read the Cochrane Review, for example, and you will see that they spend an extraordinary amount of time critiquing the methodologies of the original studies and in fact a large portion of their statistical analysis was aimed at taking into account methodological differences between studies.

    Chris

    • I will be revising my recommendations from that article. The problem with ALA is that less than 0.5% of it gets converted to DHA, which is the essential fatty acid we’re most concerned about. Rather than supplement with oils, I’ve always suggested the best course is to reduce omega-6 and eat fatty fish 2-3 times a week.

      • Hi Chris,
        Thanks for your article – well written and informative. What would you recommend vegetarians do for omega 3/6 balance? I’ve been eating chia seeds and flax seeds to help this – do you think that is enough?

      • I’m curious if you’ve done any research on the effects of fish oil during pregnancy for the health of the Baby? I’m really clueless about this and not sure even where to start reading? Any help would be great!

  15. Unfortunately these are metas which means that the original methodology cannot be critiqued. If most of these folks were taking rancid fish oil, I would almost expect these results. Almost all fish oil in capsules is (potentially) rancid off the shelf.

    • Bill,

      Most of the studies I mentioned were RCTs. The 4-year DART 2 trial which showed an increase in heart disease and mortality was an RCT. The trial showing an increase in oxidative damage from omega-3 consumption was an RCT. The trial showing an increase in MDA and lipid peroxide with 6g/d of fish oil was an RCT. The only trials that were meta-analyses were the Cochrane study and the review of fish oil trials lasting longer than one year.

  16. 3g is quite high, actually.  A 6 oz. portion of salmon contains about 1 gram of DHA.  In any event, the point of this article is that there are no studies (that I’m aware of) showing any benefit of fish oil supplementation for healthy people, especially at doses >1g/d and especially over the long-term.

    • Chris, thanks for the article. For now I’ve changed my beliefs and understandings around fish oil supplementation from this and other articles.

      Please can you clarify though, when above you say doses of more than 3g/day is quite high, you are reffering to the amount ot EPA/DHA right? Or the dose of fish oil? It’s possible Wilmar may have been referring to 3g day of fish oil which would have much less EPA/DHA in it.

      One problem I’ve found is it’s sometimes been unclear in several of the articles/studies I’ve seen whether they are talking about grams of fish oil or grams of EPA/DHA.

      The cod liver oil I have been using has approx 1.5g EPA/DHA in 10ml of cod liver oil (around 9 or 10g). This is the recommended dose. I find it hard to take for more than a few days at this dose, although I was taking double this dose intermittently a few months back. I’m now attributing it to some of the bad symptoms I’ve been getting recenty; dizziness on standing, pins and needles/tingling (induced vitamin E deficiency?), worsened vision, worsened fatigue and I hadn’t made the link, think it’s time to stop

    • Hey Chris –

      I just came across this article after reading your most recent one about scientific studies. I’m surprised (sort of) by this. I say sort if because I’ve always suspected that most fish oil supplements go rancid while in transport (hot trucks with no air conditioning).

      But up until reading this article, all if the research or articles I’ve ever read or heard of about fish oil is that it is great for you short and long term. Robb wolf (and several other influential names in the paleosphere) even recommends supplementing with 2 or more grams per day.

      Coincidentally, I recently tested my lipid peroxides and they are elevated. I have been taking around 4g of fish oil per day for about a year.

      So my questions are:

      1) I see this article was from 2010. Is this still your stance?

      2) wouldn’t cod liver oil go rancid at the same rate as fish oil? So even though it is packed with vitamins, why recommend it?

      • Hey Rick, I just wanted to address your second question because I see that Chris is recommending fermented cod liver oil. Fermented foods in general, I know can last several years without going rancid (how ou ancestors could eat foods out of season before refrigeration). I can only assume fish oil is te same when fermented. Non fermented fish oil on the other hand, you are probably right about. Also, if it is not fermented it would not contain vitamin K, and likely fewer vitamins in general. I wonder if Chris would say non fermented oil’s vitamin benefits outweighs any risk (I’m assuming not).

    • Chris, I read this and your other article. I’m very impressed. One quick question: What to do if I absolutely can’t and won’t eat any kind of fish? Won’t a “whole” fish oil supplement, something which contains the natural ratios of all omegas, 3, 6, 9 etc… as found in pacific salmon, be a reasonable compromise? Are all fish oils unstable and possibly damaging? I’m taking something made from purified wild Alaskan salmon oil, which is 3rd party certified and which contains 3, 5, 6, 7, 9 omegas. It’s made by Nordic Naturals. Won’t this be a good compromise for someone who doesn’t eat fish?

    • Dear Chris I have been taking 6 x 1000mg of fish oil for years im 42 and was diagnosed with severe dry eye and meiobian gland disfunction a year ago after taking the pill for perimenopause. I was off the fish oil for several months when I got the dry eye. Doctors tell me to keep taking it ive just come accross your information and im concerned im doing more damage than good. I need to try and keep lipids healthy in my eyes and inflammation down should I just switch to cod liver or just keep on with fish oil and how much would you recommend.
      Or should I take both.

      kind regards Bianca

      • Bianca-
        I am in the same boat as you. 40s, meibomian gland dysfunction & dry eye. Been taking more than 3g of salmon oil per day per drs orders. After this article, I’m going to follow Chris’s advice and try eating salmon 2x week and limiting my omega 3s to the amount that’s in HydroEyes. I’m scared now. Been taking high dose one has for 2.5 years.

    • Guess you’re feeling pretty silly now especially after the Virgin’s saved their son by giving him 20 grams of fish oil a day. Oh, and the doctor saved the coal miners life by giving him 18 grams of fish oil a day in his feeding tube. Seems like high doses of fish oil is key in repairing the brain.

      • You cited two extreme cases where fish oils were given at therapeutic doses to heal severe, life threatening injuries, on a relatively short term basis. The crux of the argument presented is that there are no studies where high doses of fish oil is proven to be healthy on a LONG term basis. Apples and oranges.

    • I came upon this page while researching how much oil to consume for recent heart patients, and was stuck by the similarity of your conclusion regarding long term usage of fish oil capsules, and my recent heart problem circumstances.
      I have been taking fish oil capsules for almost 2 years now, first year was 2000 mg a day, and 2nd year 1200 mg a day. Now I recently had a heart problem this month, luckily I survived ( and have not taken any fish oil caps since). But based on my young age and other circumstances, I strongly agree with your conclusion about too much fish oil or omega-3 and its link to increasing heart disease. I know you are looking for some evidence to support your conclusions, and maybe I can help you. Let me know on my email if you need.

  17. I think I can stand behind suggesting eating fish over taking fish oil, but in the event that you’re not gonna have fish that day, would a 3-gram dose of fish oil be a gross overestimation of the fish oil content you’d consume from eating a serving of whole fish?  Without being overanalytical that kind of seems like not that much fish oil.  I’d be more worried about the 10-20g/day dosers.

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