Wednesday, January 09, 2008

Essential fatty acids are essential

If you take a cow and feed it on grass it gets quite a lot of omega 3 fatty acids. If you feed it on a barley based concentrate feed it doesn't get nearly so many, just loaded up on omega 6s. Because cows have a rumen they actually live on a combination of volatile fatty acids produced by bacteria, which breaking down that otherwise useless fiber in grass, plus bacterial protein. Not much of the grass itself actually gets through to the cow. Most bovine fat is self assembled from things like butyric acid or acetate, so it's fully saturated or monounsaturated, ie typical mammalian produced fat. But some essential fatty acids do get through, after all they're essential to the cow just as much as they are to you and me.

How much PUFA get through the intensely reducing environment of the rumen? This paper gives some idea of the input and transformations which occur.

Table 1 shows the amounts of linoleic and linolenic acids in grass, concentrates and sliage. Grass and silage are pretty much the same, with one part omega 6 (linoleic, 18:2) to three parts omega 3 (linolenic, 18:3). That is, grass has a rather huge excess of omega three over omega six. Before it hits the rumen.

Concentrates don't. They're not quite as bad as the "prudent" diet of the Lyon Heart study (only a cardiologist could design a diet that bad) but, at roughly eight parts omega 6 to each part omega 3, this is still cardiological profit making nirvana for the AHA.

What comes out of the rumen? The paper next looks at the fatty acid composition of intramuscular fat, the results are in Table 3. Grass only fed cattle have about 2.33 times as much omega 6 as omega 3 fatty acids in their muscles.

I firmly believe that humans evolved with an excellent ability to hunt herbivores, grass fed herbivores. On the basis that hunting provided the bulk of the lipids to a hunter-gatherer, this looks like a pretty good fatty acid ratio to aim at. Eating wild herbivores seems to be what we were good at and what should provide us with a healthy diet. Plus a bit of fishing too I guess.

The concentrates-only fed cattle were actually given some hay too, because cows tend to die if you feed them on concentrates alone, and they came out with a 4.15 parts omega 6 to each part omega 3 fats in their muscles. It's worth noting that the worst quality of grain fed Irish beef still provides an omega 6 to omega 3 ratio as good as the intake in the best ever dietary intervention trial! Still, a ratio of 2:1 looks to be even better. In both groups the PUFA made up about 5% of the fat.

The other place worth looking is Kitava , full text here, keep scrolling down to find it and try to ignore the more weird papers written by Cordain. These subsistence farmers got their lipids from fish and coconuts. There are some omega 6 fats in both fish and coconuts, but the omega 3 from the fish predominate, ie they eat less than one part omega 6 to each part omega 3. No heart disease, despite smoking. PUFA made up 10% of the lipids eaten, which were low in total at 20% of calories.

Back to cattle. What comes out in the milk? Important if you are as dairy dependent as I am. I only have data for grass fed cattle. You can see from table 3 in this paper* that PUFA run at around 5% of lipids and that there is almost a 1:1 ratio. Omega 6 come out at or just above 1% of total lipids, omega 3 at just below 1%. Hang on, that's only 2%... What are the other 3% to make up the 5% PUFA? It's mostly conjugated linoleic acid, CLA. The good stuff, the anti-cancer, anti-this pro-that CLA. Non synthetic, straight from the cow. You can see why I like dairy fats. Cows intend calves to be healthy.

That's the grass fed stuff. In general grass is cheap and concentrates are expensive, certainly here in the UK. In areas where grass will grow and wheat won't, we grow cows. Via grass. It makes quite good silage for winter use too. If you are running a dairy unit you will feed the maximum possible of grass/silage and a minimum of cattle cake. Economics dictate this. It's a hard market for dairy farmers. But even the worst case lipid scenario, using a maximum of cattle cake, would be a 1:4 ratio in cream. This is as good as the Lyon investigators got with their gloop.

Obviously neither chickens nor pigs have a rumen, so their fatty acid balance will be far more affected by the high omega six content of their diet. This is the primary reason I add 5g/day of fish oil to my diet. It goes some way to getting an essential fatty acid ratio of about one part omega 3 to, at worst, 2 parts omega 6 overall. PUFA make up about 5% of my total lipid intake, which obviously is quite high in absolute terms, due to the total amount of fat I eat.

This seems to be a very reasonable approach to PUFA for me.

Obviously all vegetable oils except olive oil are banned from the house. Banning these oils is the biggest step needed to make balancing lipids straightforward. It's possibly more important than the gloop to the Lyon heart study success. Once you crack a bottle of corn oil, sunflower oil or a pot of margarine you will never get your omega 6 intake low enough to balance things out with a few grams of fish oil. I guess that's why it's impossible to show overall benefit form one or two cod liver oil capsules a day in a "normal" diet...

Olive oil gets used in our house as a flavouring, never for bulk calories. Actually, so does a small amount of sesame oil too...

The food has to taste good as well as being nutritious!

I don't regard fish oil as a supplement. I look on it as a tool for correcting the fatty acid defect ubiquitous in UK non ruminant fat. It even makes the excellent dairy lipids better.


*Oh, I just found that the milk-lipids paper is on my hard drive as a pdf and it's not on pubmed. No idea where I got it from! It's:

Elgersma, A., S. Tamminga, and G. Ellen. 2003. Effect of grazing versus stall-feeding of cut grass on milk fatty acid composition of dairy cows. Proceedings of the Int. Occ. Symp. of the European Grassland Federation, Pleven, Bulgaria, May 2003. Grassland Science in Europe 8: 271-274.

if anyone want's to chase it!


Anonymous said...

How do you feel about the Omega 3 and Omega 6 ratios in flaxseed oil? Seth Roberts, from where I found your blog, advocates (I think) 3 T daily.

He has also written about how fish oil is a poor source of the omegas relative to flaxseed oil. A lot of you are saying overlaps with his ideas as well as the ideas of Art de Vany.

Peter said...

The Lyon study used canola and got the goods, the omega three here being mostly linolenic acid, as per flax oil. It's then up to our own desaturase elongase systems to make the EPA and DHA our brains are made of. Fish oil and animal fat both have the longer fatty acids ready incorporated so don't rely on home production. I would certainly agree that fish oil is nowhere near 100% omega three and flax oil is close, but we've been eating fish for a lot longer than linseed oil. Makes great traditional varnish though, and smells lovely! The blue of a flax fields in flower is spectacularly beautiful too, but very new.

Oddly enough most of my closest friends are vegetarian and I noticed that you can get algae derived EPA and DHA, but this looks like a similar patch to flax oil but possibly closer to eating animals...


Anonymous said...

Macadamia oil is very low in PUFAs, like 2% or less, and also has a low n6/n3 ratio. I use mac nut oil, not olive oil. It's more versatile, and has 75-85% less PUFAs. Olive oil is like 8-13% PUFAs, mostly omega-6. I have decided to limit PUFAs to 1-4% of Calories at the most. Better yet 1-4% of total fat intake.

Coconut oil has about 1% PUFAs, and 94% SFAs. Cocoa butter has 3% PUFAs and 60%+ SFAs. Both far better than olive oil. I get 85% dark chocolate sometimes. It has like 12g of sugar in a whole bar. You can find edible cocoa butter, too.

I would definitely avoid PUFA oils: corn, soy, canola, flax, safflower, rapeseed, cottonseed, hemp, and all derived from seeds or nuts (except macadamia and coconut). Cocoa isn't a bean. Technically, it's a fruit.

Peter said...

Hi bruce,

I see your comments on Vit D and EFAs too. Interesting. I've ended up primarily on ruminant fat just from the logic of how my eating panned out. I've never really looked at nut oils in detail as I figured nuts were too high in fiber and omega 6s for bulk use. Interestingly Macadamias are my main "munching" nut when I do eat nuts, almond sponges excepted. Guess I was lucky on the EFA content... I too am willing to accept the 15g sucrose from high cocoa solids chocolate. On the mead oil front, that's is something I've never looked in to (too much to read out there) but now it's on the list. My joints, especially spine, are now normal, especially compared to how they were in my 20s when my biggest osteopath bills came through, so I guess I'm making enough mead oil at the moment. My main problem with getting EFA below 5% of total calories is that butter tastes so much better than beef dripping or suet.

I found this snippet interesting. Despite their increased unsaturation, omega 3 lipids render chylomicrons less prone to oxidation damage. Not that anyone would want to drink the amounts of oils these rats were probably given.


Anonymous said...

Peter, your dietary views are about the same as mine. I have also heard about Jan Kwasniewski's views and I think they make a lot of sense. One thing I disagree with is his advice to eat pork and lard heavily, since those tend to be higher in PUFAs by comparison to red meat and dairy.

BTW, beef fat is only 4% PUFAs. The kidney suet is 3% and muscle fat is just under 4%. Where did you get 5% as the amount of PUFAs? I'm relying on for most of my information. They use the USDA data base. They have some nice tools for searching and finding (say) what is lowest in PUFAs or highest in MUFAs or SFAs.

Another good food I found was foie gras, it has less than 2% PUFAs by total fat and like a 32:1 ratio of MUFAs to PUFAs. It's 33% saturated, about the same as most poultry fat, but the PUFAs are ridiculously low. Most poultry has 6-10x more PUFAs than foie gras. MUFA/PUFA ratio is important for Mead Acid. 10:1 ratio should increase the ratio of Mead to Arachidonic Acid. <0.4:1 is the "normal" ratio, but there is reason to believe that this is unhealthy, given the modern high-PUFA diet.

Source: Modern Nutrition in Health and Disease, 9th/10th Edition. The Chapter on Lipids and EFAD.

Anonymous said...
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Anonymous said...

Besides Dr. Jan Kwasniewski, I have also been influenced by Owsley "The Bear" Stanley. You can read his old posts on Active Low Carber. He eats mainly red meat, eggs, dairy, and a small amount of coconut and mac nut oil (based on the PUFA level). He's in favor of a zero-carb diet (below 5 grams, in the real world). He has stressed the need for 75-80% fat by calories, but he only eats 60% fat, in his 70s. He claims to have eaten zero-carb for about 48 years.

Another person that has influenced my views a lot is Ray Peat. He has discussed the issue of Mead Acid, and the toxicity of PUFAs a lot on his site. You should read some of his essays if you haven't, esp the ones on fats/oils/lipids. He even has an article against vegetables, but he's not a low-carber.

Unknown said...

Please explain more fully to mee the toxicity of PUFAs , I do not understand why they are so terribe for me.

efugeni said...

what do you think of nut oils?

Peter said...

Hi Goodwinnihon, I don't use them much but some are quite low in omega 6s, probably macadamia is the best, but I mostly prefer animal sources except for the stearic acid in chocolate...


mehitabel said...

I'm a real fan of your site, a lymphoma survivor, and an armchair cancer/nutrition hobbyest.

This is a link to a study purporting significant benefits of 25g/day dietary flaxseed in fighting breast cancer.

I don't want to believe this...I want to find fault with it...

Your opinion would be very appreciated, but I know how limited your time is.

thank you,

Peter said...


The Lyon Heart Diet study used a disgusting margarine based on linolenic acid. Flicking through the paper you cite there are no data on pre intervention PUFA levels in the patients. They will have switched a carcinogenic level of linoleic to a more favourable omega 3:6 ratio by supplementing.

My own approach is to limit the omega 6 PUFA and get my omega 3s from Food... Mostly pre elongated.


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Lipids and Fatty Acids