Fat, glorious fat. Part I

I address this subject with a certain trepidation, as there is a thin line between making science accessible and on the other hand unforgivingly oversimplifying difficult concepts.

In this first post of my Fat series I’d like to go back to the basics of fat biochemistry. If you have spent enough time in lecture theatres scribbling down the chemical formulae for beta-oxidation of fats, feel free to take a nap. If you don’t know your linoleic from your myristic, here is your chance!

Fats have received a pretty bad rep over the years. One of the most common misconceptions comes from the word itself: fat! Fat is bad! Fat makes you fat! We see these images in the media: an obese person gorging themselves on something that is considered unhealthy. You can see the glistening cheeks and mouth, thick fingers dripping oil, fat from the stomach traveling directly to their thighs. Your inner Puritan is horrified, judgement is formed in your mind even before you have consciously acknowledged it to yourself.

The media do a great job perpetuating the myth of “saturated fat clogging your arteries”. Here is a recent addition to the shock and awe campaign on fat, courtesy of the British government. As much as you want to imagine your blood vessels as pipes where you are pouring soft sticky fat mass every time you eat a burger, it bears absolutely no resemblance to what actually happens.

Fats, or better put fatty acids (FAs), are a diverse family with its own overachievers and black sheep. We mostly think of fats as something that provides calories: 9 calories per each gram of fat, the highest value out of all other macronutrients. They tell us that’s what makes us fat. But the caloric value of fats is only important if they are actually “burned” for energy. Dietary fats are used for much more than just providing calories: they are a vital component of the cellular membranes for each of the 50 trillion cells in the body. When you don’t receive enough cholesterol in your diet, your liver makes some by using the saturated fats from your food (why would it do that? Doesn’t it know that cholesterol causes heart disease?). Your brain is 60-80% fat and every neuron in your body has a fatty insulating myelin shield.
Most of us though think of fat as this stubborn orange-peel substance on our thighs, sticky soft sludge pouring through our arteries or the thick yellow deposit packing our tired liver.

So how can something so good be so very bad?

Let’s start with deciphering the common terms surrounding fats.

Triglyceride is the term commonly interchanged with fat, it consists of 3 fatty acids on glycerol backbone. Most dietary fats come into the body in form of triglycerides. Just like other animal fat, our own fat is also stored in triglycerides.

In biochemistry fatty acids are classified on the basis of saturation. The fatty acid is called saturated if carbons in its chain have a hydrogen atom at each one of the 4 available bonds. This arrangement makes for a chain which is straight and stable like a string of pearls. And because these can be easily packed together, they are solid at room temperature (think a block of butter).

An unsaturated fatty acid has at least one carbon which is missing a hydrogen. This makes the carbon form a double bond with its neighbour. Monounsaturated FAs have only 1 double bond in their chain. Polyunsaturated have obviously more than one. The double bonds in the chain give the fatty acid some interesting properties. Firstly, they are more vulnerable to the free radical attack, or oxidation, which can make them rancid. Secondly, double bonds change the shape of the fatty acid molecule: instead of a string of pearls you get a chain with a kink or two. This lowers the melting point of unsaturated fats, making them liquid at room temperature.

Here is what we are up to at the moment.

Fatty acids can be further classified by their length. Most of the saturated fat coming from animal sources is in the form of long chain saturated fatty acids: LCSFA, with >12 carbons each, for example palmitic, myristic and stearic. The carbon-carbon bond has the potential to release energy, which makes these FAs a very effective source of fuel. This is also the way your body stores them in your fat (adipose) tissue.

I think it’s important to understand the storage issue. We are so used to seeing stored fat as an inconvenience or an indicator of disease that we have forgotten why it is there in the first place. It is there to be burned. Think of it as fuel for your fireplace. You don’t collect dry timber and then get annoyed that it takes up too much room in your backyard. It is their for one reason only: to use it for energy (warm up your house) when there is a dire need. Humans have evolved to have extra energy stored away for further use.

Next question: when you stock firefuel for winter, do you use timber or rubber tyres? Both will burn, both will give off heat. But you will still choose something which is more benign and will not poison your entire family with fumes. If saturated fatty acids are so very dangerous, does it make sense that our body will carry a toxic load which will “clog your arteries” the moment it is released into the bloodstream. The fact that we have evolved to store saturated fats should be the first clue that they are the preferred source of energy and that the body considers them harmless.

If you are still with me, congratulations, you have high tolerance for dry science. Let’s plow along. Next we have MCSFAs, or the medium chain saturated fatty acids (the more common abbreviation is MCTs for medium chain triglycerides). They have between 8-12 carbons in their chains and the major dietary sources of those are breast milk (estimates range from 10-25%) and tropical oils (coconut oil and red palm). Lauric acid is a common example of a medium chain fatty acid. Unlike LCSFA, which are transported via lymphatic system in little vehicles called “chylomicrons”, MCTs travel via the portal vein from the intestine directly into the liver where they are preferentially used to form ketones. This is interesting because the conventional wisdom tells us that ketosis is always bad. So it’s kind of strange that a newborn baby would naturally receive a load of fat which encourages ketone production. Add to that the fact that your brain functions just as well (or maybe even better) on ketones and that your heart likes them as well, and there is another myth busted.

Finally, the SCSFA are obviously the short chains. Butyric acid is predictably enough in butter. But overall the dietary sources of these are very few. However, your intestinal bacteria happily produce them through fermenting fibre. Like MCSFAs they go straight to the liver.

If you are a male and therefore likely a visual learner, here is an updated pic :

Monounsaturated fatty acids, MUFA, (like oleic acid) are considered healthy by conventional standards. I, for once, agree with their assessment but for a completely different reason. The lipid hypothesis proponents support oleic acid because of their love affair with olive oil. I find it hard to believe that olive oil must be an essential part of our diet, mainly because there are plenty of regions in the world that do not naturally grow olives and somehow are still doing ok. However, monounsaturated fatty acids make up a big portion of animal fat, as much as 44% in pork lard, so it makes sense that we have evolved to process them. So if you want to increase monounsaturated FAs in your diet, fatty chunks of meat will get you much further than a tablespoon of olive oil on your salad.

Finally we come to polyunsaturated fatty acids, PUFA. They are subdivided into omega-3, omega-6 and omega-9 by the position of their first double bond if you count from the methyl (or omega) end of the chain. The FA with the first double bond in position 3 is therefore omega-3 PUFA and so on.

Animals do not tend to store large amounts of polyunsaturated fatty acids, mainly because they are not a very good source of energy. Therefore traditional animal fats are quite low in PUFA. Fish products are widely promoted for their PUFA content but while the relative PUFA composition are high compared to SFA, it is still a minuscule number in absolute terms. “Vegetable” oils (if you believe that seeds are from the same family as, let’s say, carrots) come on the top of that list. You have to eat 900 grams of smoked salmon to get the same amount of PUFA as in 1 tablespoon on sunflower oil kindly provided by the industrial processing technology. All PUFA tend to be lumped together in one big “healthy” basket but there are significant differences in their effect on the body.

To finish off just a quick summary of fat composition of common foods. Click on the table for better resolution.

Source: Wikipedia

And here is an updated diagram for you to memorise before the next post. Consider this your homework.

In the next post I will go a little deeper and talk about the “essentiality” of omega-3 vs omega-6. I will also address some clinical implications, health claims and health myths. Now go and have some fat!

Edit: a few errors which I blame on the brain fog commonly experienced after a hospital shift…

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56 thoughts on “Fat, glorious fat. Part I

  1. Excellent post – a great primer on a very important subject.

    Some edits:
    I think you mean “shock and awe campaign on fat”
    Also, “newborn baby would natural -(ly)- receive a load of fat…”

    Keep up the great work!

  2. Your explanation of the actual molecules was very helpful! I’m looking forward to the rest of the series!

  3. I’m a science junkie, so I enjoyed this review of Fats and look forward to the rest of the series. I was pleased that all the comments I could access (only the first page) under that ridiculous advert are from sane people who saw it as the garbage it is!

  4. Pingback: A little link: The Joy of Fat | Cleaning My Plate

  5. Great post. I am male and I do find visual aids really helpful. I’ve been putting together some of my own as I learn about primal health. I’m particularly working on a flow chart that shows the various ways carbs can be used by the body once eaten. It’s really helped me get a grip on these new concepts (well, new to me)… but I digress. Great post. Very helpful. Keep up the pretty pictures.

  6. Hehehe….I am a man and like visuals(wink).

    Seriously tho….excellent summary. I look forward to the rest of the series and have added you to my reading list(thanks Emily Dean for the recommendation).

    Keep up the good work!
    Geo

    • Thanks Geo, I knew I clearly targeted the right audience when my boyfriend was able to follow this post from start to finish :)

  7. Love this post! Have so posted this on the fitness transformation site, so many people just choose to diss fats (all kinds) and aren’t even aware of what they should or shouldn’t be putting into the body – we have been conditioned to think of fat and then think BAD.. whereas, we need FAT! Great post as usual, I am looking forward to the Omegas post too :)

    • Thanks Dons, fitness transformations are notorious for going ultra-low fat and then bouncing right back. Thanks for spreading the word.

  8. Your stuff, plus The Primal Blueprint plus Good Calories, Bad Calories sure makes it an easy topic to comprehend (well, maybe GCBC is a tad difficult to comprehend quickly…).
    You are doing a fantastic job in breaking down complex explanations into simple easily digestible (pun intended) chunks full of what our body and brain needs! Write a book girl and get this stuff into the head of the Australian public!

    • Fred,

      I agree with you. Anastasia is doing a wonderful job at making science much easier for folks like me to understand. I have trouble with comprehension, but I really want to learn. Wish I had had teachers like her when I was in high school.

      Susan

  9. Wow, great post Anastasia! I’m loving it for two reasons. One, I’m making the change to Primal/Paleo diet and wanting to get a better understanding around increasing my fat intake. And second, I am studying kinesiology so your posts are really helping me to integrate all that Anatomy and Physiology I’ve been studying! Thanks :)

  10. I am in love with your mind. This is another excellent post. I am currently doing a natural therapy course in nutrition – if only the text was as well written as your blog.

    • Cheeky Charlie (smiling as I type this), I had the same problem with both science and clinical classes. I was just tired of convoluted science and vague interpretations. In the end i had to write my own. Glad it helps.

  11. In a fit of pique over a “news” article, I wrote in a Facebook post that “The brain is made of saturated fat!” So a smartypants friend commented, “The brain is made up of mono & polyunsaturated fats like oleic and omega 6 & 3 acids. http://www.fi.edu/learn/br​ain/fats.html#dietarysourc​es” My gut reaction is to say, “Just like meat fat, which we call ‘saturated’”
    Help me out here, am I totally off-base?

    • Hi Gigi, at first glance I was tempted to say: yes, animal fat and saturated fat are commonly confused terms. Then I decided to look for some studies which do actual measurements of a human brain composition by fatty acids. Apart from the link you gave there was hardly anything. Lots of mentions of polyunsaturated FAs and how they are important etc. Finally! I found this study: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1963349/. Scroll down to Table 2 for the good stuff. It is looking at postmortem brains of people who committed suicide (pretty morbid, I know) but the researchers wanted to see the differences between their brains and the controls’. Guess what, they measured saturated fatty acids at around 43%, monounsaturated 22-24%, polyunsaturated 33%. If anybody finds any other study which directly measures (not estimates) brain fatty acids, please feel free to contribute.
      You and your smartypants friend can now continue your discussion armed with new information :).

      • Ah ha!! You are awesome, thanks. This just confirms my desire to take the Master’s Degree program in nutrition that my Chiropractor pointed me to… it’s most definitely NOT at the Big Ag university where I live – those are the people I’m fighting every day who think my info is not science-based. Argh. But oh Lord, the prerequisites!! LOL.

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  13. Tyler Tolman posted this little gem:
    “Pre-Marketing for pharmaceuticals #1 If your sick, Take this pill #2 If your not happy eating lard, Take this Pill #3 if your none of the above, Take this pill”

    Most wanted to take the pill but I said I’d be happy eating lard as it has a high proportion of MUFA. Tyler’s comment:
    “Sounds like a Heart attack waiting to happen :0) Ever heard the quote “You are what you eat”? just something to think about. But I’m just a Fruit, so what do I know?”
    I’m wondering was he calling me a pig!!

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    • Hi Miki. To release energy from a fatty acid it needs to go through a 4 step process called beta-oxidation. Each 4-step cycle chops off a molecule of Acetyl CoA which is made up of 2 carbons. Acetyl CoA is then sent through the citric acid cycle for ATP production. The longer the fatty acids chain (=the more carbons it contains) the more Acetyl CoA molecules can be created -> more energy released. Hope this helps to get your mind around it.

  15. Hi Anastasia,
    I know some saturated fats (such as palmitic acid) downregulate the LDL receptor. This would lead to increased serum LDL and presumably an increase in oxidized LDL. Could you explain why or why not palmitic acid is a risk factor for atherosclerosis?

    • Hi Andy. While palmitic and myristic acids do indeed down regulate the LDL receptor this doesn’t automatically lead to oxidation. Atherosclerosis has been thought of as a lipid-storage disease for a long time. Now we are rethinking this tenet and leaning more towards an inflammatory picture. High LDL are only a problem in the presence of high oxidative stress. I am more concerned about linoleic acid activating the oxLDLr (oxidised LDL receptor) and promoting inflammation in blood vessel walls. Ergo: focus more on benign toxin-free antioxidant-rich diet. The second point is that we do not ingest palmitic acid in isolation. Animal sources of palmitic acid also contain oleic acid which is known to up regulate the LDL receptor. I guess it’s not a straightforward question and context here is everything: eat SFA plus vegetable oils plus sucrose and your LDL particles are a floating atherosclerotic time bomb.

  16. Pingback: Fat, glorious fat. Part II | primalmeded

  17. Excellent post! Especially the part why we have saturated fat stored, and MCT in breastmilk, it makes it easier to wrap the brain around the fact that fat is good for the body (we have all been indoctrinated for so long that fat is bad).

  18. I have a post on fats on my blog that I think is also helpful for the layperson who may not really get all the science but who wants a guide to “fats: which to eat and which to ditch.” I think you’ll find my post is in line with your explanations above. Please feel free to send me some feedback on the guide if you have it as I’m happy to make edits to it when I gather more/improved information ay any time.

    http://balancedbites.com/2010/07/fats-which-to-eat-and-which-to-ditch.html

    Best.
    Diane

    • Cool, thanks, Diane. I reckon it’s great to have several resources for beginners. More info = better understanding. Going out for a ride now and will read it as soon as I am back :).

  19. Thanks for this post. I have been trying to understand the science behind how I eat instead of just giving a simple, “This is how we’re supposed to eat!” answer. Your explanations of the different types of fat are incredibly helpful in this regard. I am adding you to my RSS feed!

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  23. very informative, that’s what i was searching for. even if english is not my mother’s language (i’m french), i thing i get the essential and i will go and read part 2.

    • Great, I’m glad you are getting your head around it. It’s a lot to take in especially if you have been told for years that margarine is better than butter.

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  25. Making the complex simple has been my motto after I did the reverse for so many years. You appear to be making things simpler. Carry on. Earl

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