Sunday, January 27, 2013

Making the Right Fish Choices: Fatty Acid Contents of 33 Different Fish Species. Plus: What Are the Implications?

Pollachius virens (Photo: Tino Strauss) is king, when it comes to the n:3/n:6 ratio, but with <1% of fat you will still be hard pressed to get tons of omega-3s from eating pollock... but is more really better, let alone necessary?
I have already broached the issue of the differences in the fatty acid composition of fish - even those of the same species - in past articles such as the one(s) on fish as a potential source of mercury in your diet (read more). When I saw the recent paper by Claudia Strobel, Gerhard Jahreis and Katrin Kuhnt in Lipids in Health and Disease, I thought that it was about time to supply you with some real data on the actual n:3/n:6 ratio of different fish and its implications for the purported health benefits and anti-obesity effects of regular fish intake. Is there a "super fish" or is it as so often a matter of "mixing and matching" to achieve the right balance?

Fish? Of course, I have fish & chips or fish sticks every other day!

I guess I don't have to tell you that both the fish part of "fish and chips", as well as the "healthy" fish sticks that are pretty popular at least among German kids, should actually be sold at the bakery, right? I mean the ratio of the bread crumb coating to the pressed fish fillets inside, is hilarious and in view of the fact that these products are 'pre-fried' with cheap vegetable oil before they end up in the freezer cabinets of supermarkets all around the world, you cannot avoid the increased (partially oxidized) omega-6 intake, even if don't (as most people do) fry them at home.

So, if the fast-food version of "fish" is not an option to gear your polyunsaturated fatty acid ratio more towards the n-3 side of things, which fish shall you go for? Well, according to the data the scientists from the Friedrich Schiller University in Jena, Germany, collected Pollachius virens is the n3:n6 king among the seven most frequently consumed fish species, which are herring, tuna, pollock, alaska pollock, salmon, rainbow trout and iridescent shark (at least according to Strobel, 2013).
Figure 1: Content of EPA & DHA, other omega-3 and the sum of omega-6 fatty acids in percent of total fat of the 33 tested species in the study; ordered according to n3:n6 ratio, fish with the highest n3:n:6-ratios on the left; note: the anchovies and sardines were in a tin with oil and while they were drained before the analysis this will have decreased the n-3:n-6 ratio (data calculated based on Strobel. 2013)
On the other hand, the total fat content of pollock (<1%) is so low that you will be hard pressed eating enough of it to elicit any significant health effects. As far as the most frequently consumed fish species go, this does bring us back to our good old friend, the salmon.
Figure 2: Comparison of fatty acid content in g/100g of wild and farmed salmon (left) and respective omega-3 to omega-6 ratios (right; based on Strobel. 2013)
Unfortunately "salmon" does not equal salmon, these days. The dripping orange stuff you can buy for a few bucks (the orange color is artificially added to the feed by the way) at every supermarket, for example, is farmed salmon and contains only 2-3x more omega-3 fatty acids than omega-6s. The reddish, lean cuts of wild salmon on the other hand, have a 12-13x higher relative omega-3 content and in fact almost no omega-6 fatty acids (0.05g / 100g). With 0.53g /100g omega-3 fatty acids, wild salmon is yet just like pollock not the "bulk" source of omega-3 fatty acids you would be looking for, if you fell for the stupid idea that you could undo the damage you are doing by eating tons of (oftentimes oxidized) omega-6 fatty acids by simply throwing an even greater amount of omega-3s into the equation.

So what do we make of all that information?


The very latest on the effects of fish consumption on body weight comes from a study in the latest issue of the British Journal of Nutrition and shows that there is no effect of higher intakes of total, lean or fatty fish on 5-year risk of becoming obese in the 344,757 male and female participants of the European Prospective Investigation into Cancer and Nutrition (Jakobsen. 2013). Now, this does not exclude the existence of non-body weight related benefits, but it certainly puts the myth of the "anti-obesity" effect of fatty fish into perspective. After all, every 10g of additional high fat fish in the diets of the female study participants was associated with a 5x more pronounced increase in body weight than an equal amount of low fat fish. The general trend towards increasing BMIs was yet countered by none of the two.
In view of the fact that we are suffering from a relative deficiency in omega-3 fatty acids, only (relative to the exubarant amount of omega-6 fatty acids the average Westerner consumes on a daily basis), I see the data presented in this post not as a "shopping guide", but rather as a means to conduct a reality check of how realistic it really is that someone who follows a no fast- and convenient-food diet and keeps a non-neurotic eye on his overall n-6 intake will benefit from omega-3 intakes in the multiple gram range.

Specifically when it comes to supplementation, previous trials such as Filaire et al. did in fact find increases in oxidative stress in perfectly healthy athletes (judo) in response to 6 weeks on 600mg EPA + 400mg DHA per day (Filaire. 2010). If you also take into consideration that these negative effects on lipid oxidation were not ameliorated by higher alpha-tocopherol (vitamin E) levels, the message this and other studies are sending is clear: The putative increase in omega-3 requirements is a result of an abnormally high intake of omega-6 fatty acids.

The easiest way to escape any negative effects while still reaping the benefits therefore is to reduce (not totally avoid!) the intake of omega-6 fats (specifically from processed foods) - full stop! If you do that by incorporating a large variety of whole foods into your diet and include grass-fed beef, dairy from pastured cows and, obviously, fish on a regular basis, you won't have to increase your intake of omega-3 fatty acids by picking the orange colored, disgustingly tasting, fat dripping farmed salmon from the super market over its delicious red wild cousin, just because it has 4.5x more omega-3 fatty acids.

Bottom line: It's food quality and fatty acid ratios that make the difference; not the absolute numbers of allegedly good and bad fats, carbs and whatever else has recently fallen victim to the over-generalization that appears to be necessary to render dietary advice suitable for the masses. If there is any one thing that's to blame for the health crisis these days, it's this kind of black-and-white thinking that's behind the overgeneralized and faulty "expert advice" which is by no means propagated exclusively via supposedly unreliable sources on the Internet.

References:
  • Filaire E, Massart A, Portier H, Rouveix M, Rosado F, Bage AS, Gobert M, Durand D. Effect of 6 Weeks of n-3 fatty-acid supplementation on oxidative stress in Judo athletes. Int J Sport Nutr Exerc Metab. 2010 Dec;20(6):496-506.
  • Jakobsen MU, Dethlefsen C, Due KM, May AM, Romaguera D, Vergnaud AC, Norat T, Sørensen TI, Halkjær J, Tjønneland A, Boutron-Ruault MC, Clavel-Chapelon F, Fagherazzi G, Teucher B, Kühn T, Bergmann MM, Boeing H, Naska A, Orfanos P, Trichopoulou A, Palli D, Santucci De Magistris M, Sieri S, Bueno-de-Mesquita HB, van der A DL, Engeset D, Hjartåker A, Rodríguez L, Agudo A, Molina-Montes E, Huerta JM, Barricarte A, Amiano P, Manjer J, Wirfält E, Hallmans G, Johansson I, Khaw KT, Wareham NJ, Key TJ, Chajès V, Slimani N, Riboli E, Peeters PH, Overvad K. Fish consumption and subsequent change in body weight in European women and men. Br J Nutr. 2013 Jan;109(2):353-62.
  • Strobel C, Jahreis G, Kuhnt K. Survey of n-3 and n-6 polyunsaturated fatty acids in fish and fish products. Lipids Health Dis. 2012 Oct 30;11:144.

29 comments:

Javeux said...

I was pretty much forcing down canned sardines and anchovies when I first learnt about the n-3/n-6 ratio... I'll never eat one of those disgusting salads again.

Primalkid said...

What bugs me about sardines is that there are so many varieties of fish that can be called "sardines". It is annoying because it makes getting proper nutritional information difficult. Most canned versions use bristling sardines, but this one brand from Chicken of the Sea (http://chickenofthesea.com/product_line_detail.aspx?did=4800009092) is really low fat compared to the other sardines. Makes me wonder what fish they are using.

Anonymous said...

What about Krill oil?

Anonymous said...

No. Don't even touch the stuff.

George Henderson said...

Krill oil is superior to fish oil if that's what you want. It works as advertised if you're not allergic to shrimp etc. I like it for an anti-inflammatory.
Sardines come in olive oil or spring water - why choose a high n=6 soy oil brand to study?

George Henderson said...

Great blog this, BTW.

Anonymous said...

Fairly sure in most parts of the world, wild salmon is an endangered species ...

Anonymous said...

I don't think you really got it. Sardines and Anchovies are still an excellent source of n3s compared to other food, even if they contain n6s. They also contain a lot of furanic fatty acids, which might be even more important than n3s.

Prof. Dr. Andro said...

while the "you did not get it" may sound a little rude. Anonymous is actually right to point out that even bathed in oil (which is part of the reason sardines and anchovies are high in omega-6; although they have been dripped before they were tested) they still got a ratio that's superior to most other food items -- grass fed beef for example has a ratio of 1/4 n-3 to n-6 (cf. http://suppversity.blogspot.de/2011/02/grass-fed-beef-does-cla-make-difference.html)

that said your goal is BALANCE and eating foods with a 1/1 or even 5/1 ratio, only, is exactly as problematic as eating at a 1/17 ratio constantly

Prof. Dr. Andro said...

a note on the krill oil. The main difference is the degree of incorporation into the phospholipid layers of the cells; fish oil, a mostly triglyceride based N3 sucks in that departement compared to krill, which has a much higher phospolipid content cf. http://suppversity.blogspot.de/2012/06/phospholipid-or-triglyceride-whats-in.html

Anonymous said...

Wasn't intended to sound rude, maybe a little too German...
It was also my conclusion thay the n6s come from the added vegetable oil. Most sardines come in sunflower oil, while the better and higher priced verieties usually use olive oil. Those made by Appel in Germany for example. Would it be wrong to conclude that the latter should be even lower in n6s?

Javeux said...

Anonymous' reassurance still doesn't make me want to eat something that smells worse than my cat's food with a taste to match. Fresh sardines aren't so bad, but the chart and my tongue are making me lean towards the other varieties.

Maxim Okhrimenko said...

It is probably just me, but I find cat's food smell very attracting...

Anonymous said...

That's just ridiculous. You obiously never got your hands on good sardines! And yes it may sound rude, but you REALLY didnt't understand the chart...

Anonymous said...

The timing of this post interestingly coincides with an article on T-nation, which encouraged eating more omega-3 and argued that the absolute amount of omega-3 is what matters.

Javeux said...

The chart is clearly telling me I should follow my preference for salmon. I'm not comparing sardines to other food, I'm comparing them to the fish on the chart, and factoring in the idea that I don't like the taste of them. It makes the I'm going to buy salmon instead of sardines ratio high enough that I laughed at the idea of forcing down canned sardine salad. Clearly, you didn't see the funny side.

Primalkid said...

No, absolute amount of omega-3 is not what matters. You can't eat 100g of omega-6 and compromise by eating 100g of omega-3. It is the ratio that matters, and getting too much of either is harmful. Suggested reading:

http://suppversity.blogspot.com/2012/07/tta-fish-oil-revisited-increased.html

http://suppversity.blogspot.com/2012/02/tta-fish-oil-fat-burning-superfats-or.html

http://suppversity.blogspot.com/2011/03/omega-3-attenuates-exercise-induced.html

Maxim Okhrimenko said...

Living deep into continent I can only get deep frozen wild fish. And I like pickling or brining herring. Does deep freezing or this cooking techniques negatively affect fatty acids somehow (oxidation etc)?

Prof. Dr. Andro said...

you should not forget that T-Nation sells fish oil products and has a history of pretty hilarious "science articles" written for only one purpose: Make people buy their products.

Many of the workout articles, on the other hand, are quite nice - so whenever you digest a T-Nation article you got to remember that there is at least the chance of a built in bias... on another note, I guess I will have to dig up that classic rodent -40% endurance capacity study and discuss it in a post on its own to reference that in further discussions about tons of fish oil and a relative lack of omega-6

Prof. Dr. Andro said...

that's similar to eggs, it's actually less the fatty acids, than the cholesterol content that gets oxidized during frying and interestingly even more during steaming => http://pubs.acs.org/doi/abs/10.1021/jf0495946

so time = way more important than heat

Maxim Okhrimenko said...

:-\
1. Freezing not frying
2. Brining & pickling does not involve heat at all.

majkinetor said...

I don't think you can lump all w-6 together just like that. Classic all-[insert-food-group-here]-is-bad paradigm. What about beneficial w-6 that are not ubiquotus and highly beneficial like GLA and friends ?

When I totally excluded w-6 from the diet my skin changed to worse. After I supplemented evening primrose oil & blac cummin oil for few months my skin improved.

Nigel Kinbrum said...

I buy tinned sardines in tomato purée and they allegedly have an O3:O6 ratio of 1.9:1 (2.3g of polyunsaturated fat/100g product, of which 1.5g is omega-3).

I'm pleased to see that people buy far more tinned sardines in tomato purée than in sunflower oil.

Adel aka Dr. Andro said...

I once joked that they use the machine oil to package the sardines right on the fishery ships ;-)

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Lipids and Fatty Acids

cob alamin said...

Do you seriously believe nature is about ratio's?

--- Real science on why Omega 3's and 6's in "oils", not fresh nuts and seeds, turn into inflammatory lipid hydroperoxides.

The articles I linked below basically point out that exposing unsaturated fatty acids, mainly PUFAs, to light and/or heat and/or oxygen causes the unsaturated fatty acids to be converted into lipid peroxidation products, aka lipid hydroperoxides, which enhance and/or stimulate cancer growth and induce inflammation, aka stimulate PLA2 activity and TxA2 production. --- Basically refined oils are exposed to light, heat and oxygen; during and after the production. Omega 6's by themselves, in fresh nuts and seeds, are harmless by themselves unless someone smokes, inhales second-hand smoke, air pollution and other toxins on a daily basis to produce peroxidation products and stimulate excessive PLA2 activity and TxA2 production.

1997: http://aslo.org/lo/toc/vol_42/issue_6/1454.pdf (you'll need to read this to understand the 2013 paper)
2013: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3652295/ (BREAKTHROUGH SCIENCE)
2011: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3118035/
http://en.wikipedia.org/wiki/Phospholipase_A2
http://en.wikipedia.org/wiki/Thromboxane_A2

http://www.jlr.org/content/39/8/1529.full

Interesting scientific studies....

http://www.fasebj.org/content/early/2005/01/04/fj.04-2111fje.full.pdf
http://www.ncbi.nlm.nih.gov/pubmed/18293301
http://www.ncbi.nlm.nih.gov/pubmed/15522906

Lipid Oxidation: http://web.utk.edu/~jmount/Classes/515/lipidFeb17.ppt

Anonymous said...

Many sardines are packed in soy oil, sunflower oil, etc. which greatly boosts the O6 level. I suspect one of these varieties was used for these charts. Real olive oil, tomato, etc. is better and with much less O6.

Which particular fish species makes a big difference too as some contain a fair amount of O3 and others little at all. It's not clear which species were used to generate the chart.

I like sardines, but am very careful on what I buy. It needs to be packed in the right material and clearly list the various fats, including O3. At many stores, there are NONE worth purchasing. Tried to find some at a couple stores in downtown Seattle just last week and there were none that I was willing to buy.

Anonymous said...

If someone is supplementing with fish oil, bot sure why krill wouldn't be a reasonable alternative. Why "don't even touch the stuff?"

Alex aka Primalkid said...

Anonymous, have you tried Trader Joe's? That's where I buy my sardines, as they have quality sardines packed in water for pretty cheap.