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
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):
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.
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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 dissenting views, but I’m not convinced by short-term studies on the efficacy of fish oil. 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.
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Chris,
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.
Cheers,
Vin
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)?
Mike,
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.
No the dangers of heavy metal contamination cannot be understated. People should always steer clear of deep water fish. I’d go off on how ignorant that statement is but my comment would probably be removed.
Michael, give us a dietary alternative to eating deep water fish? Are we supposed to eat farm raised Talapia, which are raised in shallow plastic enclosures and fed commercial grain diets, loaded in Omega-6?
The entire food chain is compromised. You cannot live your live engaged in phobias about possible contamination of food, because every food is compromised at some level.
It’s all about intelligent tradeoffs. Deep water fish have insufficient contamination to avoid altogether, and they are a rich source of natural Omega-3 oils.
If you are going to take the position that even small amounts of deepwater fish will result in compromised health, then prove this. Where is the peer reviewed research that shows correlation between deep water fish in diet and risk of death? I don’t think you can prove your case, and showing contamination of fish is not an adequate substitute.
Heavy metals are concentrated in the fish flesh. The levels in fish oil are negligible because metals are not oil soluble
Chris,
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.
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.
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.
How do you feel about taking FCLO with butter oil, which is the version of the product that Weston Price Foundation advises to take? I guess this increases the vitamin k levels?
chris,
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.
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.
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.
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.
Chris,
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.
Paul.
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.
How about if you live in a country with abundant sun year round like Thailand. Say you receive about 30 minutes of sun exposure each day, would that be enough for vitamin D purposes and would you still recommend taking fermented cod liver oil?
Best regards, Stefan
Hi Chris,
I’m wondering is there any danger of overdosing on vitamins A and D by taking cod liver oil daily and eating organ meats once a week or once a fortnight? And/or taking raw liver pills? Might this all be too much? Thanks.
Also, you mentioned fish oil is not shown to be beneficial in healthy people – is there more of a case for it in a not so healthy/recovering person? (Autoimmune issues)
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.
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.
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.
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.
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.
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?
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.
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
http://www.omega3sealoil.com/Chapter4_3a.html
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.