Fat, glorious fat. Part II

If you have read the first post in this series and still came back for more I’m impressed. From the comments and messages that I have received (thank you all very very much) many of you appreciated going back to basic biochemistry. I don’t believe that science is an abstract concept, quite the opposite. Its applicability to everyday life is very underestimated by medical professionals and scientists alike. Either that or they believe that the public is really stupid and can’t possibly understand it. So instead they will just tell you what to do. No need to think. Baaaa.

So this particular discussion is going to be a little more in depth. I have really struggled to put together something which would be understandable but not simplistic. Please do not feel compelled to read it all at once if your eyes start glazing over. And yes, I had to skip over things and I’m hoping to get to those later.  I have about 5000 words sitting in my drafts.

To refresh your memory this is where we got to in the last post.

Let’s zoom in on PUFA. As I have mentioned before there are 3 families of PUFA: omega-3, omega-6 and some omega-9. I will leave that last group for now as these fatty acids are made in our body and seem to be less clinically relevant.

The other two families are often represented in the media and health circles as ying and yang. I don’t quite agree with that as you will see. Not a days goes by that you don’t hear of another miracle PUFA perform: from curing heart disease and diabetes to depression, weight loss and sexual performance. How biologically plausible are these claims? In other words, step 1 of the Framework of Common Sense requires us to ask a question: is it supported by what we know about human metabolism?

We know that PUFA are not the body’s preferred fuel. Instead they are an important component of cellular membranes, they initiate and control inflammation, they also participate in brain and retina formation in babies and are necessary for the synthesis of cellular messengers called endocannabinoids. Phew.

Sounds pretty important, right? However, PUFA are also involved in two of the most critical processes in our body: oxidation and inflammation. Both are essential to life, both are dangerous when they get out of control, both deserve a separate post so for now just keep them in the back of your mind

From general lets move to specifics. While the resident nutritionist on the Today show might believe that all omega fatty acids in their respective family are the same it is far from the truth.

I’m sure that all of you have heard of essential fatty acids. “Essentiality” in biochemical terms means that our body cannot synthesise these by itself and has to receive them via food. It also implies that without these essential fatty acids our health and maybe even life are seriously impaired. Two of the fatty acids in the PUFA family have been found to be “essential”: omega-3 alpha-linolenic acid (ALA from here) and omega-6 linoleic acid (LA). In the  beginning of the 20th century the studies by the Burr husband-wife team found that a lack of certain fats on a very restrictive diet makes some unfortunate rats very sick. Prior to this fats were considered important only as a source of energy and a delivery vehicle for vitamins A, D, E, K. It turned out that some fatty acids are much more than that.

Omega-3: parents, apple pies and essentiality

Let’s start with ALA. Its major function in the body is to be a parent, or the precursor, to the long chain omega-3 acids. When it is taken up from the diet it is converted to EPA and DHA, the two omega-3 siblings which cause much excitement in medical circles. EPA concentration in our body is very low as it seems to be converted immediately to its brother: DHA. However important EPA and DHA are, they are not “essential” in a biochemical sense, because we can synthesize them from ALA.

The problem is that this synthesis is not very efficient: the rate of conversion for ALA to EPA is around 8%. That is out of 1mg of ALA from flaxseed oil you will only make 0.08mg of EPA. DHA conversion rate is even poorer. It ranges from 0.5% in normal adults to 4% in young women (I’ll touch on that later).

Imagine you have decided to bake an apple pie on a Saturday afternoon. Maybe you are one of the millions of people who is still blissfully unaware that apple pie is not a health food. Maybe you will try to mitigate the damage by using margarine instead of butter. Maybe you had a rough week and you just don’t care. Back to the pie. There is no question that apples are “essential” to an apple pie. Most of us do not grow apples in our backyard or synthesise them in our bodies. You have to go and get apples from the outside source. But let’s say that the efficiency of apple:pie conversion is 8%. To get 800g of pure apple flesh after core removal, peeling, etc. you will need 10kg (Please note: demonstration purposes only. I did not actually measure apple:pie conversion so do not write saying you only needed 3 kg). To improve the efficiency of this process you can get an intermediate product like diced apples. You can even go and buy a whole apple pie, saving yourself all this headache.

In a similar way we don’t have to get our EPA/DHA from ALA (this is starting to sound like a children’s puzzle!). You can get your long chain omega-3 fatty acids directly from the diet. This way you will avoid the inefficient conversion and bypass the parent altogether. And as you know from the above, you don’t want to have to much of unnecessary oxidation-prone PUFA hanging around your body. Let’s focus on getting more bang for our nutritional buck.

And here are the long-awaited visuals.

Note: intermediate fatty acids have been omitted

This is something you need to know because the current nutritional recommendations push for more omega-3 in our diets. I will discuss the clinical evidence later but here we have the same problem as we had with every other advice: for the sake of “simplicity” all omega-3 are lumped together. Flaxseed oil, walnuts, canola oil – all contain high level of ALA, the parent molecule. They are also promoted as equally good sources of omega-3 as fish and other marine products, which are rich in EPA/DHA, the happy offspring. Meat, dairy and eggs, the way they are supposed to be (grassfed and pastured), never even get a mention.

Perfect example of opportunistic advertising

The implications are particularly important for vegetarians and vegans. And also everyone who heeds the Government advice (hello, Meatless Mondays!) and drastically reduces their meat consumption. This well-meaning study supplemented lactating women with flaxseed for 4 weeks in an attempt to increases DHA in their breast milk for the baby’s brain and retina development. The results saw a substantial rise in plasma ALA and every other intermediate fatty acid BUT the one they were actually aiming for: DHA. While it is possible that in vegetarians and vegans this process is amplified out of necessity to survive these results are still pretty poor.

Omega-6 is also “essential” but which one?

The biochemically “essential” parent FA in the omega-6 family is LA, linoleic acid. Just like in the case of omega-3 its essentiality is very relative. True, you can induce omega-6 deficiency in rats by feeding them nothing but purified sucrose, casein and some vitamins. Omega-6 deficiency was also found in very sick patients who received their nutrition via intravenous solution (TPN) with no omega-6 fats added. Needless to say that awkward oversight has seen been rectified and modern TPN solutions do not pose such issues. In reality you literally cannot take a step without tripping over LA nowadays. Ever since the happy days of Ancel Keys, McGovern committee, farming subsidies and industrialisation of food everything that is processed, packaged, patented and promoted (wow this was 4 p’s) contains this omega-6 FA.

In the body LA follows a series of reactions the result of which is a long chain omega-6 AA, Arachidonic Acid (I promise this is the last acronym). AA is a central player in the cascade of reactions which promote inflammation. Just like in my apple pie story you can also get AA directly from the diet, namely meat and poultry, eggs and organ meats. Inflammation is not all bad, it’s an essential part of our response to injury or infection and the first step of the healing process. But like all good things it has to come to an end. This is where the complexity and the innate wisdom of our bodies really hits you: AA itself promotes the synthesis of compounds which resolve the inflammation.

Note: intermediate fatty acids have been omitted

To help AA with this task we also have DHA and EPA from the omega-3 family. Therefore it is vital that we have a good balance between the key players of omega-3 and omega-6 family. I will cover inflammation and its main mediators, eicosanoids, in a later post.

One more thing to add to our little diagram is the enzymes which actually perform the conversion of short chain PUFA to long chain PUFA. Both families, omega-3 and omega-6, use the same enzymes and therefore they are in competition for them. Too much of the members of one family will interfere with the functioning of the other family. This is where the concept of a healthy 3:6 ratio comes from. High concentration of LA suppresses the conversion of ALA to EPA and DHA. On the other hand too much EPA can cause AA deficiency.

Let’s apply these new facts to a common diet and see where it leads us.

Warning: box food. Not for human consumption.

Most of the processed pre-packaged food come with a surprise addition of LA in form of soybean oil, sunflower oil, cottonseed oil, other unspecified vegetable oil. This is the source of LA which did not even exist a 100 years ago. Because you have heard about essential fatty acids and how important they are, you also go out of your way to buy health products which contain them like nuts and nut butters, seed trail mix, nut bars etc. You know all about the important omega-3 FAs so you buy flaxseed oil, walnuts and omega-3 fortified box food. The problem is that the overwhelming load of LA, inflammatory in its own right, is effectively shutting down the already-poor conversion of omega-3. And since you are getting most of your omega-3 from plant sources in the from of ALA you need that conversion!

So where does this all leave us? “Essentiality” is a biochemical concept which can be misleading if applied to the actual food. In reality the essential (=very important) fatty acids seem to be DHA and AA, possibly EPA. Even the most important PUFA are only needed in small quantities which is reflected in the composition of breast milk and animal tissues. The conventional wisdom tells us that just because they are essential more must be better. We can argue about the actual requirements (I bet you have noticed that I haven’t offered “the perfect ratio” or the required percentage of PUFA in the diet) however it is probably not very useful. Evolutionary clues should tell you that eating meat, some fish, eggs, pastured dairy and some plants will give you all the PUFA you need. Supplementing with artificial sources may just be akin to playing with fire.

Good sources of further basic information:

1. Weston A Price Foundation: Know your Fats by Mary Enig

2. IUPAC (International Union of Pure and Applied Chemistry) Lexicon of lipid nutrition  

3. DHA-EPA Omega 3 Institute (good for food sources)

4. SciTopics: Lipid Peroxidation

5. The medical biochemistry page: Omega-3, and -6 PUFAs

6. Julianne’s Paleo and Zone Nutrition: omega-3 and omega-6 post

And of course there are loads of posts from people much smarter than me like Peter from Hyperlipid, Stephan from WholeHealthSource, Dr Harris from Archevore and others addressing more intricate issues around PUFA.

Edit: a few typos and broken links, my bad.


24 thoughts on “Fat, glorious fat. Part II

  1. (I bet you have noticed that I haven’t offered ”the perfect ratio” or the required percentage of PUFA in the diet) however it is probably not very useful.”
    You made me spill my glass of red on the keyboard…Anastasia.
    Have a stab guess (like most exploring a n6-n3 ratio)..I will guess at 2/1 to 5/1 as optimum.
    The jury is still out and won’t be in for some time.
    We have a strong correlation at this stage with Diabetes,CHD,obesity etc. etc.
    It’s a good bet that causation is in there somewhere, and when it hits, we will have a reference range
    within the FBC.
    I actually discovered the cure for which there is no disease…yet!
    Although when it does..I will be able to cash in on buying adequate fish oil, krill, prime grass fed meats, caviar and wild salmon.

    • Sorry about your keyboard, Michael, but I gotta be tough on this. I think there’s enough nutritional paranoia in the world and don’t want to send anyone obsessively checking their calories and ratios.
      Both your ratio and the absolute amount of PUFA are likely dependent on the rest of your diet which will pose a big problem for anyone trying to design a study to test these ratios. Anyone who tells you the exact ratio which will save you from diabetes, heart disease and cancer is kidding themselves.
      We are lucky in Australia as most of our beef and all lamb are still grass-fed, most dairy is pastured and free range eggs are the norm. We just need to get people to eat those without fear.

  2. Oh, and it’s obviously meant to me 0.08mg of EPA. I will edit once all typos have been identified by my keen-eyed readers (this is not a challenge to go looking for them).

  3. Excellent post again! Need to read this one again so I can digest it properly! 🙂 So all this extra fish-oil is maybe contraproductive?!

    • Hi again ReRunnr. This post was definitely meant to be read in several chunks I just didn’t have the heart to break it up. Taking fish oil might be useful for those on the Standard Western Diet although long term studies seem to be controversial. If your diet doesn’t contain excess amounts of omega-6 you need much smaller amounts of omega-3. I’m not saying never have any fish oil, just think about how much you are having and why.

  4. Thanks for the clarity! I do have a question. Where I live the only grass-fed beef I can find costs about 3x the hormone and antibiotic free beef I usually buy. If I’m eating no vegetable or seed oils and no processed food (I cook in animal fat only), how important is it to bite the bullet and buy the grass-fed stuff? Would eating a serving or two of salmon a week be advisable? (I hate fish.)

    • Hi Ron, obviously there is no study re PUFA consumption in Paleo-like diet. So anything we say here would be a speculation. If you remove the competitive inhibition by omega-6 then you likely reduce the absolute requirement for omega-3 also. Provide enough saturated fatty acids for energy. It could very well be that the stress you will experience eating fish can outweigh any positive effect from its consumption 😉

  5. Thanks Anastasia! While I’ve spent quite a bit of my time studying up on fat & carb consumption, the lipid hypothesis, metabolism of sugars & insulin, and the conversion losses in fatty acids, etc etc…. this is one large piece of knowledge I was lacking. Being aware that omega-3 fatty acids are beneficial, I assumed supplementing them was important (given the success of several studies demonstrating it as one of the few supplements in the market that actually does something), and given your post, still think it’s vitally important for everyone following “conventional wisdom”. However, since I have already cut out over 90% (arbitrarily assumed) of my industrial oil consumption, my LA consumption has decreased considerably, so omega-3 supplementation may be unnecessary at this point.

    I have one question regarding this. If EPA -> DHA conversion uses the same enzymes as omega-6 FA, it shouldn’t be an issue for people who do not depend on proinflammatory industrial oils (like myself). According to your chart, there appears to be no direct source of DGLA. That leads me to believe that abandoning the parent source of omega-6 fatty acids eliminates the competition for desaturases and elongases enzymes responsible for conversion in each step.

    If one follows an actual heart-healthy diet (low-carb, no industrial oil), it seems that there is no harm in consuming omega-3 supplements (albeit unnecessary) since there is a lack of enzyme competition. In my understanding, the majority of packaged and restaurant cooked food uses high doses of LA oils. The conclusion I’m drawing is that it’s good insurance to take fish-based omega-3 supplements unless one homecooks everything. Please feel free to point out any grave miscalculations in my hypothesis. I’d rather look stupid now if it makes me more knowledgeable in the future. It is important that I have a clear understanding of this since the majority of fish-based omega-supplements have a higher portion of EPA than DHA.

    P.S. If you have any education regarding lectins, I would highly encourage composing an article on it. There seems to be a lot of conflicting information on it.

    • Hi Raphael, thank you for your question. To supplement fish oil or not on a healthy diet (sigh): I wish you luck in finding clarity on this point. It might just win you a Nobel prize. It is certainly above my level of expertise. But I can add a couple of points.
      First, there is actually a dietary source of GLA (later converted to DGLA): it’s borage oil and evening primrose oil. I have never bought/used/seen any so I think we can safely dismiss it as a food source. 
      Second, we can make DHA from EPA via another pathway called Sprecher’s shunt which does not use a desaturase.  This still doesn’t change the fact that the conversion of omega-3 from plant sources is pretty darn useless. If you want your EPA/DHA stick with animal/marine sources.
      Even after completely eliminating vegetable oils from your diet you will still be getting some LA from animal fats. Thats why there is no such thing as LA deficiency (even though it’s an essential fatty acid) in a human who eats actual food. 
      Omega-3s in general certainly displace AA in tissues. And supplementing with fish oil might speed up that process. Or it might contribute to the overall oxidative process. Even if your diet was very inflammatory prior to this it might still be better to stick it out and wait for the tissue ratios to correct gradually. Experience tells us that every time we discovered something and ran away with it as the next best thing we inevitably missed a crucial part of the picture. You wouldn’t eat salmon daily. Why replicate it in a pill with questionable ratios? 
      I hope this helps. Geez it’s hard to have intelligent educated readers 🙂

  6. that’s great thanks, i’ve read many places about O6:O3 ratio and it being important, modern diet being too high in O6 etc etc

    but this is the first time anyone has mentioned the enzymes and the two O types being in competition.

    that has connected an important series of “dots” in my understanding

  7. I like the playing with fire analogy, as I read dynamite has 6 double bonds, and linseed oil (painters use) its flax oil in a less refined, I believe has 4 (please correct me if I’m wrong) – and will burst into flames if left on rags. Thus, I’m a little concerned about people taking much more than a tablespoon of PUFA, even from omega-3 fish/cod liver oil. Should I be (or does the Vit E protect from this oxidation reaction at the cellular level)? I know the RATIO of 3:6 is important, but seems like I have read we might still, overall, try to limit 6:s to around 4 grams/day (with 2 gms omega-3 as offset)?
    Great blog – thanks! Angelo at LAtest in Paleo sent me!

    • Thanks Deborah. Angelo has a great thing going and I’m very flattered by his comments. It’s ironic how linseed oil has made a seamless transition from furniture varnish and solvent into a health food item. You might find my answer to Raphael covers your question as well. And yes, I share your concern about absolute amounts coming from artificial sources.

  8. Hi, love your blog and can’t believe you are doing it in Med school! Your rant post was great, you have a lot of self-control – the ignorance and egos in the medical world are staggering!
    Anyway, this is a much needed series for a lot of people. So thank you.
    I have a few questions: what does it means that PUFA’s oxidize, and SFA’s don’t and how exactly does that start the cascade off to inflammation. (and if the body doesn’t store PUFA where does it go?)
    thank you for your hard work!!

    • Hi Herbie, thanks for your thoughts. I will attempt to write a proper post on oxidation at some point. Oxidation is basically a by-product of metabolism, resulting in formation of free radicals = compounds which can initiate inflammatory response, cell membrane damage and affect DNA inside the cells. Normally this process is offset by antioxidants both produced in the body and received from food. PUFA are inserted into cell membranes and are more vulnerable because their double bonds are an easy target to initiate the oxidation cascade. When the oxidative load becomes overwhelming and antioxidants cannot catch up we talk about “oxidative stress”. It is closely linked with inflammation because it both promotes inflammation and is also used as part of the inflammatory cascade. Both processes are linked to heart disease, autoimmune disease, Alzheimer’s, cancer and many others.
      Look out for my inflammation/oxidation post for further details. Also Chris Masterjohn has written extensively on lipid peroxidation on PUFA on his Daily Lipid website and Weston A Price foundation website. Hope this helps.

  9. Great summary!

    Also not to be missed:
    “Precious Yet Perilous — Understanding the Essential Fatty Acids” by Chris Masterjohn

    Bottom line for those wanting to know how much omega-3 to supplement:

    “I think that unless you’re treating something specific that is responding well to higher doses, you should probably limit it [cod liver oil] to 0.5 or 1.0 teaspoons per day, and this should be in the context of a diet rich in egg yolks, butter, liver, etc.”

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  16. You have managed to take some of the mystery out of the omega 6, 3 questions.
    Thanks alot for a very easy to understand post.
    I have been taking omega supplements for some time, and over the years I have changed my choices. I now take a supplement from Jarrow that claims a 2:1 ratio.
    I also give my dogs and cats supplements. I have been giving some Grizzly Salmon oil along with cod liver oil. It is my understanding that at least dogs have a similar need for omegas in the same ratio. I read different ingredient levels in salmon oil.
    It seems that cod liver oil has mostly EPA and DHA along with vit A and D.
    Maybe it would be better for canines.
    With all the other sources of Omega 6 in our diets, it seems that we should just take Just Omega 3’s EPA and DHA.

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