"There's only one hard and fast rule in running: sometimes you have to run one hard and fast."








Wednesday, October 6, 2010

Eat Real Food (omega-3 edition)

There seems to be no end of discussion about omega-3 fatty acids. I've gone through pretty much all of it, including Barry Sears' Zone Diet take on why omega-6 fatty acids are bad for one (odd, as one is absolutely essential for survival).
Let's briefly go through the basics of the different fatty acids. Our bodies are really good at making saturated fats, which are the simplest in structure and these are the oft-vilified fats of artery-hardening fame. Monounsaturated fats differ from saturated fats by having one double bond, polyunsaturated fats have more than one. Trans fats are polyunsaturated fats that are chemically modified to remove and alter some double bonds; when our bodies do this, all the bonds are in one form (called "cis"), but  when done chemically, half are in cis form, half trans. Our bodies can't deal well with trans fats, because they aren't naturally occurring.

The whole argument about why some of these are better than others comes down to the fluidity of cell walls, which are made of fatty acids. Arteries that are flexible have fluid cell walls and cell walls are made fluid by the spacing of fatty acids. The differences can be compared to drinking straws: saturated fats are like the paper wrapper found around some straws - straight, but limp. Trans fats are like straight drinking straws. Monounsaturated fats are like flexi-straws that have a kink in them. Polyunsaturated fats have multiple kinks, bending back and forth in a zigzag. If you take one end of each of these and roll them between thumb and forefinger, the opposite ends move through different-sized circles. The greater the circle, the greater the space needed to keep them from hitting each other, thus the greater the fluidity. On this basis, trans fats are terrible, polyunsaturated and saturated better, monounsaturated good - and the closer that bend is to one end in monounsaturated, the better (which is why omega-3 is better than omega-6 or omega-9). Current standards suggest that less than 7% of one's calories should come from saturated fat, up to 10% polyunsaturated and up to 20% monounsaturated. Top sources of monounsaturated fats are olives (and olive oil), canola oil, nuts (especially walnuts) and avocados; cocoa has monounsaturated fats, but  even more saturated fats. Top sources of polyunsaturated are safflower oil, soybeans (and oil) and corn oil.

Our bodies can turn saturated into unsaturated and unsaturated into saturated, with a few exceptions. There are two fatty acids we can't make, alpha-linolenic acid (ALA) and linoleic acid, and because of where their double bonds are, the first is called an omega-3 fatty acid, the other an omega-6. Two omega-3 fatty acids that particularly important in brain development (and thus found in breast milk) are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); we can make these from ALA, but many believe that there are real health benefits from ingesting them. EPA and DHA are found in high levels in fatty fish, as they help keep cell walls fluid at the low temperatures these fish usually inhabit.

Omega-3 fatty acids are not very stable and degrade when exposed to air, which is why fish oil supplements are sold in gelatin capsules. The omega-3's in plants are usually found in conjunction with chemicals called lignans, which help preserve them; lignans have anti-oxidant properties and are phytoestrogens, sometimes mimicking the effects of the hormone estrogen to a small extent, sometimes impairing estrogen's effects (the health effect of lignans are debatable, but should be considered by those with cancer).

Here's the sources of omega-3's, in rough order of quantity:

Seafood: salmon, sardine, mackerel, herring, cod liver oil, trout, scallops, snapper, haddock, tuna.
Plants: flax seed and oil (whole flax seed is indigestible, it must be ground first), purslane, walnuts, canola oil, soybean oil, hemp seed, sea vegetables (algae), dried beans and other legumes, squash.
Other: eggs (must be labeled omega-3 enriched, as it comes from the feed), lamb.
Avoid these: evening primrose and borage supplements (they have weird ones of dubious use and can be contaminated with who-knows-what).
For those interested in omega-6 fatty acids, the best sources are safflower, sunflower, poppyseed, wheat germ, soybean, sesame, corn oil, cod liver oil, peanut oil, canola oil/rapeseed.

24 comments:

RBR said...

Ooooh! Now you have done it!

I love nerdy SQ posts! (Shut up, G)

I will be back later with questions!

Glaven Q. Heisenberg said...

There are two fatty acids we can't make ... (ALA) and ... [blah, blah, blah]

Woo-hoo! Thanks for the shoutout! ALA = American Library Association ...

Hey wait ... RBR? You're good at finding veiled fat insults where there are none ... Did SteveQ just call all of us librarians Fat@$$es?

(Uh, and by "us" I don't mean YOU, B*tch! Geez! You're no librarian!)

sea legs girl said...
This comment has been removed by the author.
sea legs girl said...

Glaven, I'm back to give you a hard time again. It should actually be written - "where there IS none", not "where there are none". I thought you worked with books (I'll get you to respond to me one day).

Steve, I'm just glad you remembered to metion rapeseed.

sea legs girl said...

I suppose if I am going to make fun of Glaven, I had better spell mention right.

Deb said...

Bummer...I just swore off rapeseed. Guess I'll stick with my diet of Doritos and Little Debbies and drop dead within the next year or three.

Ross said...

I'll admit to not having read the primary research, but there seems to be something to the idea that it is the ratio of omega-3s to omega-6s that is most important in regulating the inflammatory response (and no, I'm not talking about Glaben's comments).

The standard diet is normally relatively high in o-6s, so one needs to either decrease the 0-6s or increase the 0-3s.

nwgdc said...

So what are your thoughts on the Udo's Oil fad?
It seems we need more omega-3's to balance the ratio, so why follow Scott Jurek's suggestion and take a supplement with o-6's?

By the way, I hold a nutrition class every month at the office and hammer home omega-3's. I've never thought of the straw analogy. I love it and am stealing it.

Glaven Q. Heisenberg said...

@sea legs girl

Subject = "insults"; complement "none" (in this case none = "no insults"); correct verb? Plural = "are".

I am correct, amn't I?

"There" being, of course, neither plural nor singular, inherently, it should go without saying ... assuming, of course, that this is where the confusion lies. Because if it is and you think "there" is singular? There is many things we need to discuss.

Also: If you're looking for bad grammar to nitpick? You should really read my blog. Because it is just chock full of solecisms. Because can you believe this? Because I routinely begin sentences with the word "because" - making that part a subordinate clause? And then I don't supply a main clause in the same sentence? Making the whole sentence, essentially, a fragment? And what's with those fucking question marks, you might well ask?

And why, knowing this is wrong, do I do this, you might ask, too?

Because.

wildknits said...

Interesting...

Been consuming a lot of herring (fresh water variety) of late - and a bit of lake trout. Gotta love being related to a commercial fisherman.

Will now need to do some research on Lake Superior herring and see if this fish is as high in Omega-3's as it's salt water cousin(which is what I am assuming you were referring to).

Glaven Q. Heisenberg said...

Sorry about your Twins. I'm of two minds, though. C. Manuel has said he'd like to see a WS re-match between us and the Yankees. I can understand that. But the Yankees being the Darth Vader of baseball and all, we non-evil people just want to see them get beaten. I had no personal stake in the Y.s last series with the Red Sox, but took a perverse glee* in their being denied their division by their hated rival who weren't even in the hunt for post season glory.

Plus, I hate just presuming the Phils will be in the WS. Still gotta win two series first.

Doc last night was a decent start: No hitter; 1 RBI.

_______________
*And by "glee", I mean I broke into song while music and choreography spontaneously broke out around me and I was O! So gay!

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SteveQ said...

@Nic: Udo wasn't on my radar. I looked him and his product up (how "famous" can he be if I haven't heard of him until now?); once again, I say EAT REAL FOOD - it contains evening primrose oil, among other things.

@Ross: The ratio of o-3 and o-6 ingested has no proven lasting effect on the ratio in the body! The inflammatory response, as related to prostaglandins coming from arachidonic acid (technically an o-6) is immaterial. If one really wanted to change that, a baby aspirin does more.

@Wildknits: lake superior herring have the same fatty acid profile as their saltwater kin.

RBR said...

1. Teacherly appreciation

If you take one end of each of these and roll them between thumb and forefinger, the opposite ends move through different-sized circles. The greater the circle, the greater the space needed to keep them from hitting each other, thus the greater the fluidity.

Beautifully explained. I like to call it the "elbow room principle" but I am juvenile.

2. Shit, this comment has been unfinished for an hour and a half now. I give up. I have to read up on fatty acid metabolism.

Of course, I took it in a completely different direction (as I always do with your science-y posts)

I am particularly interested to the observed correlation between the ingestion of relatively low levels of trans-fats (particularly 18:2 as opposed to 18:1, although I am not clear why and I do not think they are either) and the observed decrease in essential fatty acid conversion and the observed decrease oxidative phosphorylation in the mitochondria of rats (possibly secondary to decreased osmoregulation? as evidenced by the observed swelling, perhaps? I do not know and I have not had time to read the reference)thereby, creating a need for increased consumption of essential fatty acids.

You eat one type of fat that necessitates the need for more fat? Super.

I have no spent the last 3 and a half hours reading scientific papers on fatty acid metabolism and NOT working on what I am supposed to be teaching today.

I think I will go have a Twinkie and mull all of this over. Don't worry I will wash it down with some salmon.

SteveQ said...

And it's "where none exist." Proper word choice trumps proper grammar.

Ross said...

Well, that's a problem with epidemilogy - proof is hard to find. Correlative evidence is more the norm. And lasting effect? How long is that? Until your next meal?

This review article is interesting. As I've said, I've not read the primary literature.

http://ebm.rsmjournals.com/cgi/reprint/233/6/674

SteveQ said...

@RBR: Poesy appreciation. "Elbow room" succinctly captures the idea. Wish I'd used it.

Can't help you with the reference unless you tell me what it is. I haven't read EVERYTHING - yet.

RBR said...

Not exactly cutting edge research, but I had to back track since my knowledge of fatty acide metabolism was "weak sauce" at best.

Here is the reference. Bell rang, so I will look for a link when the cherubs go away.

Takatori T, Phillips FC, Shimasaki H, Privett OS.

Effects of dietary saturated and trans fatty acids on tissue lipid composition and serum LCAT activity in the rat.

Lipids l976;l 1:272-80.

RBR said...

And you haven't read everything?

Oh, how my hero has fallen.....

*hand to forehead, dramatic sigh*

RBR said...

Oops, and here is the referencing article. That would help, I imagine :)

http://www.ajcn.org/cgi/reprint/34/10/2307

ok, working now.

SteveQ said...

Now I have some reading to do...

Ross: I was intentionally vague because I don't have the numbers in front of me. A first glance of the review has me thinking that what is needed is to show that an individual changing diet will have changes in internal markers, rather than correlating markers to diet in groups - but that's tricky - and it IS an interesting review. I'm going to have to brush up on my c. elegans epigenetics.

RBR: I'm just starting to look at the Lipids article.

21 comments so far (if far fewer commenters)!

SteveQ said...

And I have to switch "linoleic" and "linolenic" throughout the post. I always make that mistake.

RBR said...

@G, SLG, and SQ: the ever present fat insults DO exist therefore I, and my third grade grammar, trump you all!

*smiles smugly at her own overt self-centeredness and horrid use of the English language*

I can not decided if I am more insulted that I was called a fat ass or a librarian. [shudders]

wildknits said...

Steve, thanks for for checking out the profile (somehow I knew you would know).

Herring catch is up right now, 700+lbs and that is with one net partly tied up. Yup - herring will be in my diet for some time to come. ;->