When it comes to fish oil, more is not better

October 25, 2010 in Food & Nutrition, Heart Disease | 95 comments

Article summary

  • fishoilmedication
  • 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:


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

{ 95 comments… read them below or add one }

Wilmar October 25, 2010 at 9:08 am

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.


Chris Kresser October 25, 2010 at 9:12 am

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.


Bill DeWitt October 25, 2010 at 9:28 am

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.


Chris Kresser October 25, 2010 at 9:38 am


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.


ben October 25, 2010 at 9:37 am

Does this mean the 2g of jarrow / vital choice fish oil recommendations should be stopped, or reduced?
Perhaps the plant based, omega-3 ALA from flax seeds, etc might be a better option.   Less chances it oxidizes than fish oil (EPA/DHA), and if nothing else, ALA promotes glutathione


Chris Kresser October 25, 2010 at 9:41 am

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.


Chris Masterjohn October 25, 2010 at 9:51 am

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.



Cathy October 25, 2010 at 10:14 am

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.


Hans Keer October 25, 2010 at 10:33 am

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.


Jay October 25, 2010 at 10:39 am

Does this include krill oil?  I’ve been eating fish 3 times a week and taking 2 krill oil capsules.


Preston October 25, 2010 at 10:46 am

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.


Julie October 25, 2010 at 10:50 am

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.


kg October 25, 2010 at 10:53 am

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…


Chris Kresser October 25, 2010 at 11:06 am

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.


doug October 25, 2010 at 11:08 am


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)



shaecim October 25, 2010 at 11:23 am

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?


Chris Kresser October 25, 2010 at 11:51 am

Yes, I think so.


Chris Kresser October 25, 2010 at 11:52 am

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.


doug October 25, 2010 at 12:09 pm

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.


Jake October 25, 2010 at 12:32 pm

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.


Chris Kresser October 25, 2010 at 12:41 pm

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.


Sarah October 25, 2010 at 1:58 pm

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?


Chris Kresser October 25, 2010 at 2:01 pm

400 IU is probably not sufficient to maintain levels in an area with little sunshine, so taking 2,000 IU is probably a good idea.  But the only way to know for sure is to test your levels.  ”Test, don’t guess” sums up my strategy nicely on this – and many other issues as well.


RHS October 25, 2010 at 2:44 pm

I have been using seal oil for about 3 years because of chest pain
and it has helped.  IMO much better than
fish oil and the oxidation factor.  Read this



Chris Robbins October 25, 2010 at 2:46 pm

I’m on the side of limiting fish oil consumption and upping ones fish consumption. I think high levels of omega-3 are probably beneficial if you live in sub-zero conditions, but otherwise I believe the benefits of fish come from taurine & to a lesser extent magnesium.


knittymama October 25, 2010 at 3:13 pm

I’m also curious about what those who can’t eat fish should do. My son has a potential fish allergy is is currently taking a soy free algae based DHA supplement. I also worry about my other sons eating a lot of fish due to contamination issues (plus they just don’t like it anyway). Suggestions?


Chris Kresser October 25, 2010 at 3:54 pm

The algae oil is DHA, which is beneficial in moderate amounts.  You don’t have to worry about mercury, dioxins or PCBs in most commonly eaten varieties of fish.  See this article for more.


Dave October 25, 2010 at 9:34 pm

Given your continued recommendation for Green Pastures FCLO, do you have any thoughts on dosage for children? Are 2 yr old has been taking 1/2 a teaspoon every since he could eat solid foods.

Second question, does a person who currently takes high dosage of fish oil to relieve the symptoms of Rheumatoid arthritis have an alternative?
Thanks in advance for any thoughts you may have on this.


Chris Kresser October 25, 2010 at 9:42 pm

Young kids with rapidly growing brains have a greater need for DHA than adults, so I’d say continue with that dosage.

People with autoimmune and other chronic diseases may also have greater omega-3 needs.  I guess my first question would be what is their intake of omega-6 like?  The first thing I would do is dramatically reduce that, before taking high doses of fish oil.


Chris Kresser October 25, 2010 at 9:50 pm

I’ve been using Meriva-SR with inflammatory conditions like RA. It’s a slow-release curcumin bound to phosphatidylcholine, which improves absorption. I’ve never had much success with curcumin in the past, because it’s poorly absorbed and gets rapidly taken up in the bloodstream. This product addresses those issues and seems to work better.

But, as with all autoimmune diseases, the key is balancing the immune system and addressing the underlying mechanisms.


Dave October 25, 2010 at 9:54 pm

Thanks for the quick reply!
My omega-6 intake could probably be reduced significantly, which is in the works as we speak. When talking about dosage for people like myself with RA, should I be taking FCLO or straight fish oil? FCLO does not disclose the EPA/DHA levels.


Chris Kresser October 25, 2010 at 9:58 pm

There is some data listed on FCLO on their website: http://www.greenpasture.org/retail/?t=products&a=test-data

The levels of EPA and DHA are low, but as I said in the article, so are our needs provided we’re eating a healthy diet.

I recommend FCLO over fish oil for everyone for the reasons I outlined above. The fat soluble vitamins play a large role in regulating the immune system – especially vitamin D.


P. Winter October 25, 2010 at 10:07 pm

Great article, you mention eggs, if you have  no access to pastured eggs, or even if you do, then fish eggs are a great choice, fish roe is a cheap source & I eat it once a week with the occasional kina ( sea urchin eggs ) . I think that fish eggs provide you with iodine.


Stabby October 25, 2010 at 10:23 pm

Obviously if they’re oxidized to oblivion they’re no good. I can’t help but think that the mixed results of fish oil supplementation have to do with the poorly abosrobed ethyl ester form. I just can’t see a bit of oxidation being worse than not being able to turn off eicosanoids properly. In either of those cases the data wouldn’t be a true reflection of better quality fish oil.

And of course nobody is going to debate that some wild salmon is preferable to any fish oil. There is also the wonderful and very paleo option of BRAINS.


Another Dave October 25, 2010 at 10:57 pm

It is worth noting that the DART 2 researchers disagree with your interpretation of the results. From the paper: “An adverse effect of fish oil as distinct from dietary fish is unlikely.” There is a good discussion in the paper of some reasonable explanations for their results. They seem to think that the result may not be statistically significant but also bring up the possibility that the fish oil group may have engaged in riskier behavior or skipped their usual medications due to the belief that the fish oil pills were adequate. The study was an RCT designed to evaluate the efficacy of dietary advice, not of fish oil supplements, and thus should not be taken as evidence against fish oil supplementation.


Marilla October 26, 2010 at 12:55 am

What are your thoughts about CLO that isn’t fermented? My plan was to finish the full bottle I have (Healthspan) and then buy Green Pastures. Am I getting any benefit from the Healthspan CLO or could it be doing more harm than good? BTW, I’m eating a healthy diet with no processed foods, no seed oils etc.


theo October 26, 2010 at 5:46 am


consumer labs is an independent lab that analyzes various OTC supplements for contaminates, listed ingredients, etc. Their more recent review of fish oil did not show any problems with rancid oils in the products they tested (with the exception of one fish oil product for dogs). Theoretically, there is a risk of rancid oils when taking fish oils, but it doesn’t seem to be as big of a problem as one might think. i agree we really need more long term studies with fish oil to give it a thumb’s up.


Chris Kresser October 26, 2010 at 8:51 am

Another Dave: it is worth noting, but I’m not convinced by how researchers interpret their own data if their interpretation isn’t sound. I’ve seen so many studies clearly indicating that saturated fat or cholesterol doesn’t cause heart disease, for example, but the authors of said studies find a way of “interpreting” their data to support the dominant paradigm. This is a well-known phenomenon in medical research.

Marilla: the advantage to fermented CLO is that 1) it is cold processed and thus the naturally occurring vitamins remain. Non-fermented CLO is generally heat processed, bleached and deodorized, which destroys the natural vitamins. Synthetic vitamins are added to compensate for this. 2) Fermented CLO has vitamin K2, which non-fermented CLO does not. That said, nonfermented CLO is still beneficial at a moderate dose. So continue with what you’ve got and then switch to FCLO.

Theo: in this article I’m talking about the oxidation of omega-3 fats in the body – not during the production or storage of the fish oil, which is an entirely different issue. Even if you consume absolutely fresh fish oil, it’s still much more vulnerable to oxidative damage due to the fragile structure of the fatty acid – as depicted in the 2nd figure in this article.


Masont March 31, 2011 at 2:13 am

I think it’s also important to note that the study was done on men with angina. Studies done on people with pre-existing heart conditions aren’t 100% applicable to healthy individuals. If an organ isn’t functioning properly from the onset it’s reaction to stimuli would be different than that of a healthy organ.


Mike October 26, 2010 at 9:14 am


Great write-up, as usual; that first study you listed can be viewed in english via Google translate.

As per my comments via Matt’s blog, the LDL increase is a positive result of fish oil intake: the shift from VLDL to LDL. This is in addition to the beneficial effect of lowered trigs:

“Since the increase in LDL and consequently in total cholesterol levels appear to be due to the increase in the conversion of VLDL and LDL in the negative regulation of LDL receptor observed by other researchers. The increase in the concentration of LDL appears to be due to increase in size, which would be very favorable for the increase in the size of the molecule makes it less atherogenic (28,29).”

“Our data showed increased oxidative stress observed by increased levels of MDA in 45 days of treatment, but there was no change in levels of hydroperoxides assessed by CLT. It was found that the QL is a more sensitive and specific than the TBARS and suffers less interference in the assessment of oxidative stress in patients with MS (35,36). Thus, it is concluded that ingestion of fish oil does not increase oxidative stress.”

There still a lot to explore about fish oil, especially from a lipid peroxidization standpoint; I’ve personally seen too many benefits over the years to throw it out—myself, extremely low Tgs, elevated LDL and HDL, improved body comp to <7%, recued DOMS and increased athletic recovery, all at 6-9g/day EPA/DHA over the last 3 years.

Had I had a massive amount of lipid peroxidatization going on, I would have suspected decreased health and performance.

Whole food will always trump singular supplements any day of the week, but in the case of marine food, the source is extremely questionable at best.


Chris Kresser October 26, 2010 at 9:23 am


Thanks for your comment.

I agree that more research needs to be done here. In particular, we need to see how fish oil affects people whose intake of n-6 is already very low. Unfortunately, I doubt we’ll see a study like that anytime soon.

Concerns about toxins in fish are overblown. I’ve written about that here.


Thomas October 26, 2010 at 1:05 pm

I love it-sacred nutrition cows keep falling! We were so convinced of the benefits of Omega-3 supplements. Remember everyone saying we shouldn’t be afraid of fat, as long as it’s the good kind (omega-3)? I wonder what’s next? Vitamin D (it’s pedestal seems a little too high at this point)?


Vin Kutty October 27, 2010 at 11:09 am


I own and run a specialty fish oil company. So you’d think I’d be upset about your post. I’m not.

Lately, we’ve been telling our customers to cut back on n-6 fats. We try to educate them on how to do this. The ‘reduce n-6′ message is on our blog, our emails, brochures and product inserts. Frankly, it’s bad business – I should be pushing more n-3, not less n-6.

But it’s the right thing to do.

To my customers, I’m their fish oil source. In my customer’s minds, it often does not compute why I’m asking them to eat less corn and soy oils. Our reduce-the-6 campaign is backfiring a little bit because it is like a car company asking people to ride bikes more often.

Your readers are an elite bunch. They get it. But most regular people just want a pill to fix their problem – they don’t want to know what caused the problem. Some of my customers get it – and they love it! But for the others, we’re trying a slightly revised approach now: less n-6 = less n-3 pills = save money!

They key is reducing n-6. As for oxidation, yes, it’s a problem. It’s a problem before the pills are made. It’s a problem while the product is ‘on the shelf.’ It’s a problem after consumption. This is not new. Double bonds have always caused problems. You will be reading more about this in the next few years – I know of some good research under way.

I’m a nutritionist and my peers are not collectively ready to discuss this yet. Your post nudges us in that direction. But I hope people don’t skim your post’s title and conclude that fish oil is now to be avoided. The Paloe-elite can drastically reduce their n-3 pill consumption. But most Americans can’t. They’re drowning in n-6 and fructose.

For now, I’d advocate less than 1 or 2 grams of n-3 per day. It’s a risk-benefit thing. In the meantime, those taking > 5 or 6 grams n-3 per day for years should expect some oxidative damage.



Chris Kresser October 27, 2010 at 11:12 am


If only more supplement and drug manufacturers shared your integrity and concern for your customers’ well-being. Thanks for setting such a good example.


Kevin October 27, 2010 at 1:08 pm

Good post!

But I need to consume 2 gram minimal a day of Fish oil because I eat 50 gram, sometimes more, almonds a day and 4 or 5 eggs. This alone is about 8 grams of omega 6 which I need to belance with 2 gram Fish oil. So in my case it wouldn’t be smart to supplement 1 gram I think?


Chris Kresser October 27, 2010 at 2:49 pm

Kevin: I always suggest minimizing omega-6 before increasing omega-3.


Kevin October 27, 2010 at 3:09 pm

Even if that means dropping or reducing quality whole food packed with very good nutrients? Sorry, I don’t agree with that :) .


Chris Kresser October 27, 2010 at 3:18 pm

Fish oil is not a quality whole food packed with good nutrients. Whole fish is, though. Which is why I suggest people meet their omega-3 needs by eating it instead of taking fish oil.


Kevin October 27, 2010 at 3:47 pm

I meant almonds and eggs as nutrient dense food, not the fish oil.


Craig Giddens October 27, 2010 at 4:56 pm

No wonder people get so confused and give up trying to take the path to good health without the aid of the drug companies. I’ve been working hard to get my Triglycerides down without drugs through low carb eating, but felt like fish oil would be a big help. Now I am confused!


Chris Kresser October 27, 2010 at 5:17 pm

I think there may very well be a place for a “pharmaceutical” approach to fish oil. By that I don’t mean Lovaza, the drug company branded fish oil. I mean taking a short-term course of fish oil to accomplish a specific purpose, such as lowering triglycerides, or to reduce inflammation. The dangers I mentioned in the article seem to occur over a period of years.

I highly recommend a paleo diet for fixing your lipid profile, if you haven’t done that already.


Craig Giddens October 27, 2010 at 5:20 pm

I think people are going to get confused when they are told something is good, but then told it could be harmful.

“I think fish oil is a much better choice than aspirin. Both have blood thinning effects, but fish oil has other benefits like balancing the omega-6 to omega-3 ratio and isn’t harmful to the liver.”

Chris Kresser


Ron Lavine October 27, 2010 at 5:32 pm

This is an interesting sharing of ideas. The last few months I’ve been convinced that a “balanced fatty acid” pill with fish oil, borage, and flax seed is the way to go, but now I’m not so sure. I was unfamiliar with the idea of fermented cod liver oil – that sounds like its worth checking out.

Fundamental to a lot of this discussion seems to be the issue of how badly screwed up an individual’s diet is to begin with before we try to modify it and/or supplement it. And also how much an individual can be motivated to change it.

There are days when I feel on target and that I can be a good motivator of patients. On other days I’m not so sure. The secrets of being influential in how inspiringly we share information (not just on the technical correctness of our information) seems critical.


Chris Kresser October 27, 2010 at 5:35 pm


I am always learning and growing as a practitioner and a researcher. I try keep an open mind, consider other points of view, and change my approach when new information warrants such a change. I understand that this can be frustrating and confusing for those that come here hoping for answers.

That said, the statement you quoted above doesn’t necessarily contradict what I’ve written in this article. I mentioned that fish oil has been shown to benefit those with pre-existing heart disease or those who’ve had a recent heart attack. Many people who take aspirin for cardiovascular protection fall into this category. Note that I was not recommending high dose fish oil supplementation in any of those previous articles, either.

Also, I still do believe that taking 1-2g/d of fish oil is less harmful than taking aspirin. These aren’t black or white issues. For example, aspiring is less harmful than statins, but that doesn’t mean it’s benign. Likewise, high-dose fish oil is probably less harmful than aspirin, but nor is it benign.

I do need to revise the series on EFAs to reflect this new information. Hopefully I can get to that in the next couple of weeks.


Chris Curley October 28, 2010 at 7:41 am

Hi Chris,

a few questions:

I am a newbie to Fermented CLO. Oxidation occurs both within and without the body. If CLO is fermented does this not allow oxidation to occur?

What are your thoughts on Krill oil. Krill oil contains a natural antioxidant astaxanthin(?) inherent in its makeup and is presumably less susceptible to oxidative damage.

I have been hot on the trail of this subject for about a month as well and have come to find a product by Europharma called vectomega. It is a “whole food” supplement of purportedly whole salmon heads pressed into a pill. The manufacturer claims that this phospholipid based form allows for easier assimilation and less oxidation. Are you familiar with this product?



Chris Kresser October 28, 2010 at 8:07 am

Oxidation will still occur. It’s a matter of scale. I believe the benefits of taking FCLO every day (vitamins A, D, K2, E & quinones in their naturally occurring form) outweigh the potential risk of oxidative damage, provided overall intake of PUFA is low and B6, magnesium, and other nutrients that support fatty acid metabolism is adequate.

I’ve never heard of vectomega. One possible advantage of krill oil, as I wrote about in my article on fish oils in the EFA series, is that the omega-3s are in phospholipid form, which should be better absorbed. But my thoughts on krill oil in general are the same as my thoughts on fish oil.


JB October 28, 2010 at 7:47 pm

Thanks for the post very interesting. I have a couple questions. When you say 1g/d of fish oil are you referring to total fish oil or just the EPA/DHA? The fish oil I am currently taking is 1200mg capsule with 410 EPA and 274 DHA. Would you you be recommending 1 capsule (1200mg) or 2 (1368 mg EPA/DHA)? I also saw you recommended a “higher dose” for children. Do you have specific numbers for that? I have 2.5 and 4 year old boys.



Alan October 28, 2010 at 7:57 pm

I know that you advocate eating fish such as canned alaskan salmon.

The question I have is why can’t whole fish oxidize in your body just like fish oil? Or is it just the degree of potential oxidation! Does the whole fish have more antioxidants and greatly prevents oxidation.

As usual, another great post. Thanks for your effort.


Ahrand October 29, 2010 at 2:22 am

And once again Weston A Price is right, do not take ‘nutrients proven by science ‘ but take food proven by generations of healthy families : grassfed butter, liver, fish bone broths. We are not (yet) smart enough to determine exactly what nutrients in which combination have which advantages.

Look at healthy populations and try to emulate and be vary wary of refined and extended shelf life foods.


Chris Kresser October 29, 2010 at 10:06 am

JB: the 1g/d refers roughly to the total amount of polyunsaturated omega-3s. So it depends how much of the 1200 mg capsule is omega-3, not just EPA & DHA. For kids, “higher” dose refers to higher relative to their body weight, not higher in an absolute sense. So very young kids can take maybe 1/2 the adult dose, or a little less, and it will still be higher relative to body weight.

Alan: yes, it’s the degree of potential oxidation and the fact that whole foods like salmon have more antioxidants.

Ahrand: I agree completely.


Razwell October 30, 2010 at 5:27 pm

TREMENDOUS article, Chris. I am so glad this information is getting out there. I always have felt the whole Inuits thing was based on some faulty assumptions. They eat whale blubber and meat, and this contains all the nutrients working in concert, not processed fish oil pills.

Also as you say, the Maasai, Kitivans do fine without all the marine oils.

Take care,



David October 30, 2010 at 5:59 pm

What about fish oil for depression?


Chris Kresser October 31, 2010 at 8:29 am


For depression, my recommendation is the same as it is for general health: the first step is to dramatically reduce omega-6 consumption. Then, eating fatty fish like salmon 2-3x/week and adding a moderate amount of fermented cod liver oil should help balance the n-3/n-6 ratio. That’s the intention behind fish oil, after all, but this is a safer way to do it.

That said, if someone has done all that and they’re still not getting the results they want, and additional fish oil provides a benefit, I’d choose that over an SSRI any day of the week.


Bentzurm November 6, 2010 at 5:04 am


You have not mentioned the omega3-index blood tests in your excellent fish oil posts. Would you agree that the following would be wise:
- reduce dietary omega6 to a minimum, while taking moderate amounts of fish oil (or FCLO) for 6 months (to reverse years of SAD).
- test your membrane fatty profile and either increase or decrease fish oil accordingly.
- retest in 6-12 months and repeat.


Chris Kresser November 6, 2010 at 8:15 am


Yes, that would be wise. I did mention the omega-3 index in this article. Scroll down about 2/3 of the way.


Vin Kutty November 10, 2010 at 11:28 am

Hi Chris, an interesting counter-point here…but I have not read the full study, just the abstract. Frankly, I wasn’t even aware of this journal.

Mas E, Woodman RJ, Burke V, et al. The omega-3 fatty acids EPA and DHA decrease plasma F(2)-isoprostanes: Results from two placebo-controlled interventions. Free Radic Res. Jun 2010.



Suzy November 13, 2010 at 12:05 pm

From the Green Pastures link you posted for their “Product Test Data” – under additional comments it says “Majority of D is D2″. I’m concerned – I thought it would’ve been D3 – do you know why that is?

Also, do you know what this means: “below .090 PPM PCB WHO/exceeds Prop 65″ ?

Thanks for the very informative post.


Chris Kresser November 13, 2010 at 1:01 pm

Suzy: it has D2 because that’s what naturally occurs in the cod livers, apparently. We know less than we think about how all of the various constituents of vitamin and mineral complexes behave.

The second part means that the detectable levels of PCBs exceed the WHO and California Prop 65 standards.


Suzy November 13, 2010 at 8:02 pm

Chris, thanks for your reply. So now I’m confused because from my understanding it’s the D3 we’re after. I was hoping to use FCLO as a somewhat whole food source of vitamin D (more for maintenance than boosting my levels). But now it looks like it’s actually the wrong kind of vitamin D? Could you please shed some light on this for me?

As for the second part about Prop 65, that’s what I was worried it meant, but was hoping that I had misunderstood it. I’m surprised to hear that their FCLO exceeded the standards. I always thought that FCLO was one of the “safer” alternatives. Could you please share your thoughts on this?

Thank you.


Chris Kresser November 13, 2010 at 8:08 pm

Suzy: exceeds the standards means “is better than”.

Eating vitamins in their natural whole food form is always the best choice. When supplementing, D3 is more desirable than D2, but that doesn’t mean we would avoid cod liver oil because it has more D2 than D3. As I said in my previous reply, there’s still a lot we don’t understand about the various constituents and how they work together.


Suzy November 13, 2010 at 8:38 pm

Chris, yes of course. I was so focused on toxins exceeding safe levels or allowable limits, that I completely misread the “standards” part. Thanks for your insight re: FCLO.


andy November 15, 2010 at 2:47 am

thx for another great article.
Prof. Brian Peskin has been advocating agains fish oils for a long time, more info
Also google ‘IOWA study on fish oils’, and you also see that fish oils makes worse

B.Peskin has been advoacing for consuming good ratio of omega 3:6, and then body would be able to produce enough DHA and EPA. Whilst consuming fish oils we get pharmacological doses of DHA and EPA, which is harmful, could even lead to diabetes, CVD, cancer.
He got a term parent essetial oil (PEO), – which basicly means high quality omega 3 and 6 (alfa linolenic and linoleic fatty acids)


Bruno November 15, 2010 at 10:55 pm

Hi Chris,

What is the dose recommended of omega 3 caps? 1 gram a day???


Chris Kresser November 16, 2010 at 9:21 am

Best to just eat fatty fish 2-3 times a week, and take 1/2 tsp/day fermented cod liver oil from Greenpasture.org.


Marion November 28, 2010 at 12:41 am

I have been taking fish oil for my arthritis — 3600 mg daily. I am 61 and was an avid distance runner until felled by hip arthritis (now both sides). I had stopped running entirely and was in such pain that I had scheduled hip replacement surgery for last August. I read an article about 5 months ago, however, that said that most people fail to benefit from fish oil because they do not take enough. By the time I had my pre-op visit with my surgeon, my arthritis have improved markedly — so much so that my surgeon was no longer willing to do the surgery. I was able to begin running again with my running group (3 miles on trails) and had significantly less pain. From my reading of the scientific literature, fish oil has been associated with relief from joint pain (due to its anti-inflammatory properties and other unknown effects). Would you recommend from your assessment of these new findings that I stop or reduce my intake?


Chris Kresser November 28, 2010 at 9:24 am

Marion: my recommendation is to dramatically reduce omega-6 intake, eat fatty fish 2-3 times a week and take 1/2 to 1 tsp. of fermented cod liver oil per day for all of the reasons I described in this article.


Jack Kronk November 29, 2010 at 3:30 pm

Hi Chris,

Love your site. I frequent regularly.

I was just thinking about all the sources I get omega-3 from, and started wondering if I am maybe getting too much.

I eat salmon about once a week and I have canned tuna once a week (the only brand I buy is Wild Planet. they do it very differently with very high omega-3 and low mercury and no oils and no water added)

I eat a significant amount of Organic Valley’s pasture butter, probably about 4 tablspoons per day, which claims naturally occuring omega-3.

I take Green Pastures Fermented Cod Liver Oil / Butter Oil blend daily.

I also eat at least 2-4 organic eggs from free roaming chickens and sometimes they claim omega-3 on the package depending on where I buy them from (not always though).

So that’s 3-4 significant sources of omega-3. Is that too much?


Chris Kresser November 29, 2010 at 3:36 pm

Those are all excellent food-based sources, and provided your intake of omega-6 is low and you’re eating a whole-foods, nutrient-dense diet (which it sounds like you are), I think you’re right where you need to be.


Tedd December 5, 2010 at 10:09 am


I agree with your article; it just makes sense. My problem is the rest of my family, who continue to eat bread, and sometimes pasta. Is the lesser of the evils to supplement with 3-4g high-quality fish oil to counteract the too-high intake of omega-6′s? Or would it be better to live with the higher omega-6 intake and limit the fish oil to 1g?


Chris Kresser December 5, 2010 at 10:22 am

Tedd: bread isn’t high in omega-6 (but it does have other problems, such as gluten and the impact of refined flour on blood sugar), so it’s not the issue in this case. Foods high in omega-6 are packaged, processed and refined foods containing industrial seed oils like corn, soy, cottonseed, sunflower, safflower & canola. Chips, crackers, cookies, fried foods, etc. Also restaurants use these oils almost exclusively.

If someone continues to eat those foods, it’s difficult to say what the lesser of evils would be. The best of the worst choices would be to get them to eat fatty fish 3-4x/week. If not that, then in the short term 3-4g/d of fish oil would probably be beneficial… but as the studies I mentioned in this article suggest, that effect would diminish over time and even reverse.


Tedd December 5, 2010 at 10:34 am

Thanks. Your post will serve as a reminder for me to get vinegar and oil on the side when I order salads. I sometimes forget to do that. That’s probably the one area where I get too much omega-6′s.

On a possibly related note, I’ve had tinnitus for two years now, and I’ve taken high doses of high-quality fish oil for 15 years. It might be a coincidence, but after going on a strict gluten-free diet about a month ago, and recently cutting out fish oil (6 days ago), my tinnitus is only about 1/5th the level it used to be, and has been at that lower level for five days now. I’ve experienced this low level before, but never for more than 2 1/2 days in a row.

I took the fish oil to reduce inflammation, but maybe it backfired on me!


Chris Kresser December 5, 2010 at 10:35 am

Yes, it’s possible. And you’re the 2nd person in a week to mention a connection between gluten and tinnitus. That’s something I wasn’t aware of – although frankly, it doesn’t surprise me.


Lee December 22, 2010 at 11:02 am

I have been taking roughly 4400 mg. of high quality fish oil plus 2000mg. of niacin-(not the no flush) for a year and recently had labs done. My HDL increased to 105, my LDL decreased to 105 and my triglycerides decreased to 52. In addition, my last carotid artery scan showed a reduction in velocities (which means less plaque). I attribute this to the combo of fish oil and niacin. I eat a very low carb diet and am type 2 diabetic with an a1c of 5.6. After reading this very thought provoking article, I am thoroughly confused.

I definitely need to educate myself on this issue.

Thank you for your astute article.


John Waters (Aust) December 28, 2010 at 11:08 pm

This is interesting stuff. I have a peculiar condition of longitudinal grooves in each thumb nail. Various MDs have suggested there is an infection or damage to my nails, But I don’t agree as there are no other signs. but when nails are placed end to end, the groove is in precisely the same position on both nails and they are quite deep. This has been developing over the last 20 years.

I have been using fish oils for several years together with other supplements. Three months ago I started taking 4000mcg of fish oil daily and now it is obvious that my new nail growth is almost smooth and normal. This indicates that the fish oil is promoting good nail growth. I don’t know what it is doing to other aspects of my health.

I will have a full blood analysis soon, so it will be interesting to see if my usually high LDL is reduced. I eat fish twice a week and otherwise a nutritious omniverous diet. I am 69 and maintain an excellent BMI.


Nigel Kinbrum February 6, 2011 at 10:51 am

Hi Chris,

1 small can (213g) of Alaskan Wild Red Salmon contains ~20g of oil, of which ~6g is EPA & DHA. I can easily eat that in one meal!

Eskimos eat both oily fish and marine mammals. Marine mammals run at a higher temperature than oily fish, so they have a lower percentage of pufas in their fat. Even so, Eskimos are eating a diet high in long-chain omega-3 pufas but they aren’t dropping like flies from CHD & cancer (although they may age prematurely).

Therefore, is it reasonable to conclude that the omega-3 pufas naturally present in foods = O.K. so don’t worry about them?

Cheers, Nige.


Nigel Kinbrum February 8, 2011 at 11:10 am

So, is “So I still recommend eating fatty fish a couple times per week…” overly restrictive?


lex February 13, 2011 at 11:38 am

Hi Chris, this article is interesting, but worrying! I have hashimotos thyroiditis and am avoiding iodine containing food as it definitely worsens the auto-immune attacks – they rocketed after I went on Summer holidays and overdosed on fresh fish and shellfish. I have been taking krill oil tablets on the basis that they don’t contain iodine? Does FCLO contain Iodine? would this be a safe option for hashimoto’s?
Would appreciate your thoughts!


Chris Kresser February 13, 2011 at 8:54 pm

Lex: I don’t think food goitrogens play a significant role in suppressing thyroid function. I prefer FCLO to krill oil because it also has fat-soluble vitamins A & D.


Matt March 8, 2011 at 8:24 am

Chris: Excellent discussion! Where do monounsaturated fats fit into the picture? Myself and many of my Paleo friends have been consuming quite a bit of almond butter and avocados. Do you see any problems arising from this. To my knowledge almonds are much higher in mono than poly unsaturated fats and assuming that we are not eating processed foods and the dangerous seed oils would this be OK provided we are balancing with FCLO and fatty fish a couple x a week?


Chris Kresser March 8, 2011 at 9:49 am

MFA are perfectly safe. However, both almonds and avocados contain a fair amount of omega-6 so consumption of these should be moderated.


Iain Lettice April 10, 2011 at 8:51 pm


I had a heart attack 5 years ago and have taken Omacor (1 * 1000mg per day) since. I’m not sure if this is a good or bad thing now. Could you tell me?




Iain Lettice April 13, 2011 at 5:56 pm


I had a heart attack 5 years ago and have taken Omacor (1 * 1000mg per day) since. I’m not sure if this is a good or bad thing now. Could you tell me?




Christian O'Grady April 20, 2011 at 8:06 am

Would be interesting to see what these peoples other nutrient intake was like…

We know fats with double bonds are easily oxidized. Did these people have adequate fat soluble vitmains and antioxidants to avoid oxidaiton?

Like anything we cant draw too many conclusions from such little infomation and such a little picture. Health isnt 1 nutrient or pill. Its a lifestyle, and when that lifestyle can be studied would be interesting to see the results.


Christian O'Grady April 20, 2011 at 8:06 am

Would be interesting to see what these peoples other nutrient intake was like…

We know fats with double bonds are easily oxidized. Did these people have adequate fat soluble vitmains and antioxidants to avoid oxidaiton?

Like anything we cant draw too many conclusions from such little infomation and such a little picture. Health isnt 1 nutrient or pill. Its a lifestyle, and when that lifestyle can be studied would be interesting to see the results.


Christian O'Grady April 20, 2011 at 8:06 am

Would be interesting to see what these peoples other nutrient intake was like…

We know fats with double bonds are easily oxidized. Did these people have adequate fat soluble vitmains and antioxidants to avoid oxidaiton?

Like anything we cant draw too many conclusions from such little infomation and such a little picture. Health isnt 1 nutrient or pill. Its a lifestyle, and when that lifestyle can be studied would be interesting to see the results.


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