Talk:Alpha-linolenic acid

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linolenic acid related in treating eczema and acne?

Contents 1 Moved From Article- 2 Abbreviations: 3 Correction for 3D molecular image. 4 Doubt on thylakoid as source of n-3 5 spelling 6 Trans-Fats and Soybeans 7 ALA and Trans fats - the Kinney reference 8 Bio Sources table

[edit] Moved From Article-

A mutant strain of flax, Linola, has been developed in Australia which is low in linolenic acid and high in linoleic acid as compared to natural flax. (should appear instead on the n-6 page Istvan 16:08, 7 November 2005 (UTC))

[edit] Abbreviations:

LNA = Linolenic Acid - 18:3 (any form)

ALA = Alpha Linolenic Acid - 18:3Δ9c,12c,15c "Omega-3"

GLA = Gamma Linolenic Acid - 18:3Δ6c,9c,12c "Omega-6"

PUFA = "Polyunsaturated Fatty Acid" Any chain length with two or more double-bonds.

[edit] Correction for 3D molecular image.

Using Argus Lab (http://www.arguslab.com/) I obtained a different 3D geometry for alpha-linolenic acid. When I was unable to conform it to the displayed geometry here, I searched for additional 3D models online and found that additional online sources also disagree with the geometry given here. For example see: [1] and [2].

The image I've uploaded has the same conformation as 1. Source 2 does not specify whether the double bonds are cis or trans. Either way, I don't think they disagree.

Ben 17:16, 14 September 2006 (UTC)

To me, all the images look like they have the same structure, even if the geometry is a bit different. Organic molecules can have a great deal of flexibility, especially long linear ones. The different images depict different conformations of the same molecule. --Ed (Edgar181) 10:57, 16 September 2006 (UTC)

[edit] Doubt on thylakoid as source of n-3

The text says that ALA is the most abundant oil in thylakoid. But grasses have plenty of thylakoid (don't they?) and have almost no ALA. I suspect that the statement may be true about thylakoid in dicots (broadleaf plants.) Also, the n-6/n-3 ratio varies quite a bit for nuts and seeds, as attested by how walnuts show up in the list of good ALA sources. David.Throop 11:15, 18 September 2006 (UTC)

[edit] spelling

is it hyphenated or not?

[edit] Trans-Fats and Soybeans

Ive changed the recently added passage on ALA in soybean oil but would rather delete it for being misleading. Firstly, hydrogenation does not produce trans-fats, as it leaves (virtually) no unsaturation; Partial hydrogenation (as noted in the reference) produces trans-fats and should be referred to as such. Secondly, ALA is not the "cause" of trans fats in partially hydrogenated soybean oil, but rather contributes to the reason it is partially hydrogenated, i.e. to increase shelf life. Breeding (or in the case of soybeans: "breeding") low-ALA soybeans, even no-ALA variety, will not remove trans fats from partially hydrogenated soybean oil; not partially hydrogenating it is the only thing that will avoid this. As written, pinning trans-fats on ALA misleads the casual reader into mistakenly believing that ALA is somehow culpable for trans fats when it is in fact partial hydrogenation. Thirdly, press releases placed by the soybean council are often stealth advertising (remember the "tropical oils" scare of the early 90s?). If nobody comments, revises or objects then I will delete this passage. István 21:08, 5 January 2007 (UTC)

I'm happy to see my language cleaned up, and your call on partial-hydrogenation vs hydrogenation is a good one. But it is true that during partial hydrogenation, PUFA react and form trans-fats as a side-product. According to the article I cited, the main problem comes from the thrice-unsaturated ALA (rather than, apparently, the twice-unsaturated linoleic acid, also abundant in soy.) The fact that there's a market and a premium price for low linolenic soy beans seems to be appropriate to this article. As for the tropical oils scare... IIRR, that was mostly the work of that Naderite outfit, CSPI. See Enig. (Yeah, I know, Weston Price... but it checks out.)

I've also read that there are high-pressure hydrogenation beds that add the hydrogen without converting the cis bonds to trans but I don't have a ref handy.David.Throop 22:39, 5 January 2007 (UTC)

Of course you are correct, PUFA do indeed form trans during partial hydrogenation, but so do mono- and di-unsaturates, as will *any* aliphatic with double bonds. To single out the triene misleads the casual reader into believing that trans fats cannot form from e.g. linoleic or oleic when they certainly do. The premium now for low linolenic soy (as for high oleic safflower, sunflower etc.) is paid because it can enter many of the same applications without the processing, and without the trans fats which are quite nasty actors, as we are learning. I believe the point of the paragraph (which, I agree is certainly germane to this article) should be that low linolenic soy has a longer shelf life than does conventional soy, and this removes the need for partial hydrogenation in some applications. Certainly I wish the soy growers luck in their "breeding" as this will indeed be one big step toward solving the national obesity problem. —The preceding unsigned comment was added by Istvan (talk • contribs) 03:00, 6 January 2007 (UTC).István 03:02, 6 January 2007 (UTC)

The higher the unsaturated fraction, the faster the oils will oxidize. The more double bonds, the higher the chance of one of them rearranging to trans. What our discussion shows is that we need a section not just on trans fats and soy, but also discussing rancidity and oxidation.

I disagree with you, though. I think that the rancidity rate is much higher for the tri-unsaturates than the di- or mono. (Olive oil hardly goes bad at all while flax oil goes fast.) And I'd expect that linolenic acid would show a correspondingly higher rate of trans fat formation. That's what the news article seemed to say, too. David.Throop 03:51, 6 January 2007 (UTC)

I certainly dont dispute that the triene will oxidise more rapidly than the diene or monoene (see above) and that this is the point of the article referenced. I disagree that a low-linolenic soybean oil will result in fewer trans-unsaturation as this would certainly depend on the entire fatty acid profile; or that (as originally, perhaps unintentionally, implied in the article) a low-linolenic soy oil would produce a trans-free partial hydrogenate (which it certainly would not), and perhaps not even a lower-trans (depending on total FA profile).István 04:08, 6 January 2007 (UTC)

Here's the claim from Monsanto

ADM To Process Monsanto's VISTIVE™ Low Linolenic Soybeans At Indiana Facility Agreement Expands Growing Area for Soybeans, Which Provide A Trans Fat Solution to the Food Industry

ST. LOUIS (Jan. 12, 2006) - Monsanto and Archer Daniels Midland Company (ADM) announced today that ADM will process Monsanto's VISTIVE™ low-linolenic soybeans in 2006 at its facility in Frankfort, Indiana, and will market the low-linolenic soybean oil for use by the food industry. VISTIVE low-linolenic soybeans will reduce the need for partial hydrogenation of soybean oil, helping food companies reduce the presence of trans fatty acids (trans fats) in their products.

For the 2006 growing season, ADM will be contracting with growers in Indiana for up to 40,000 acres of VISTIVE soybean production. ADM will pay a premium to producers who grow VISTIVE soybeans under contract. Then it will crush and sell the processed soybean oil to food companies.

VISTIVE soybeans, developed through conventional breeding, contain less than three percent linolenic acid as compared to the typical eight percent level found in traditional soybeans. The result is a more stable soybean oil, with less need for hydrogenation. Because soybeans with a lower linolenic acid level reduce the need for partial hydrogenation, their application in processed soybean oils will reduce the presence of trans fats in processed soybean oil.

RTWT David.Throop 05:24, 6 January 2007 (UTC)

Precicely: "low-linolenic soybeans will reduce the need for partial hydrogenation of soybean oil", and not "will yield a lower trans-fat level in its partial hydrogenate". The salient point is that partial hydrogenation may be avoided altogether and not that low-ALA soy renders less trans fats from partial hydrogenation. Do you read it differently? István 05:38, 6 January 2007 (UTC)

Yes, somewhat. If they are still putting it through hydrogenation, they're still going to yeild at least some trans-fat. However, they can list the trans fat content as zero if there's less than .5g trans fat per serving. They say less need for hydrogenation not no need. My reading is that they're still putting it through the hydrogenation tanks, but the contact time with the catalyst will be much reduced and they'll get the trans fat content low enough that they can label it as zero. BTW, the issue isn't shelf-stability. It's stability in the frying baths. And, to a lesser extent, the mouth-feel — the oil is thicker and more full tasting after partial hydrogenation. I made some small changes to what you wrote, and I added the Monsanto cite.David.Throop 07:53, 6 January 2007 (UTC)

We're still seeing one point differently - firstly, agreed: stability = frying life = shelf life = oxidative stability = rancomat (or OSI) hours; this was never contested. However, the Monsanto ref claims that a low-ALA soybean reduces "the need for partial hydrogenation" and will result in "less hydrogenation". I read it as clear reference to the "prevalence" or "frequency" of hydrogenation (and partial hydrogenation) at the collective/macro level, and not as reference to "shorter" hydrogenation runs. This is common sense - a shorter 5% brush hydrogenation will yield more trans isomers than will a longer hydrogenation running 95% to completion (total unsaturation reduces as the reaction progresses). Furthermore, it does not follow that a more stable, lower-ALA soybean oil would (all else being equal) produce less trans isomers in the partial hydrogenate. Changing the fatty acid profile (typically 15% saturate, 22% monoene, 55% diene, and 8% triene) by cutting the triene in half does not describe the total FA profile (this was conspicuously absent in the reference) and in fact when hybrids do succeed in altering the FA profile they virtually never shift cleanly - I would be willing to bet that the cited 4% drop in triene is also accompanied by a drop in saturate and monoene, and a much greater than 4% rise in diene - i.e. that FA profile would certainly yield a more stable oil, but would not clearly have any less total unsaturation than traditional soy (as is very common given identical growing conditions). But the article doesn't go there, and is clear enough as it is written: fewer applications would require a low-ALA soybean oil to undergo (any) partial hydrogenation because of the new oil's improved stability. István 08:38, 6 January 2007 (UTC)

[edit] ALA and Trans fats - the Kinney reference

Thanks for finding this, its an interesting one. Ive looked over it and it describes a more oxidatively stable oil which allows utilisation in several applications (most notably frying) without having to undergo partial hydrogenation, and not "less" (shorter) partial hydrogenation. If you wish to revert my edit, I would request that you point out specifically which slide (perhaps I missed it) on the Kinney presentation which states that the new GMO soy (G168-12 and L2494*HO7-9) may be used in an application with "shorter" partial hydrogenation. To me it looks like G168-12 and L2494*HO7-9 offer a trans-free alternative and not a "lower-trans" alternative for u.a. frying oil. Do you read it differently? István 22:21, 11 January 2007 (UTC)

I'll take your revision; it's OK. Yes, the Kinney paper is very interesting. Oddly, I found it today when I was Googling on 'Thromboxane A3'. I wasn't even looking for soy. There are a lot of gems in it. I find it boggling that they're planning to produce EPA-rich soy—and they're using a desaturase that converts AA into EPA! They're also (apparently) planning to make a conjugated linolenic acid – similar to conjugated linoleic acid – from GM soy. "Oh brave new world! to have such vegetables in't."

I expect that this whole section may eventually spin off into its own article. – David.Throop 23:52, 11 January 2007 (UTC)

No kidding - 4 or 5 gene insertions, and for them to all express?! They got the bucks I suppose.... I know the fish will be pulling for them. István 03:06, 12 January 2007 (UTC)

[edit] Bio Sources table

Nice work on the Dietary Sources table. I added Soy and Canola. They are relatively low in linolenic acid, at least compared to the other sources listed in the table. But because of their prominence in the world diet, they are probably contribute more ALA to the human diet than any other sources do. Indeed, I've read (can't immediately find site) that the increase of soy and canola oils in the US diet (at the expense of corn oil and cottonseed) has improved American's omega-3 status substantially. David.Throop 15:30, 29 January 2007 (UTC)

I agree on their inclusion due to their importance, however it would be best to pick a single number (as all are actually ranges) When putting together the table, I used a method to select published results (the SOFA is an excellent site for this) and simply took the average. This works well for all but Sea Buckthorn (which seems to fall into one of three levels - the above one is very generous - I would put it at 27% at best) and for recently revived crops such as chia and kiwi which are now being hybridised for n3 (and thus the %ALA is going up quickly) and for others like flax where there is a lot of genetic engineering for various reasons, giving some big outliers. I saw the source data (p773) gives a range. I would probably go through the SOFA and pick a single number (there are probably over 100 hits for each) apples to apples and such. István 15:57, 29 January 2007 (UTC)

OK. Also added a footnote within the table noting that this was the average over a range.David.Throop

Moved this poorly placed, half-attributed text to TALK: Danish biologist, Maria Jensen, MINSA's natural scientist and health researcher, added a source of linolenic acid; nigella sativa [black seed].+ Our website; www.minsa.org.za —The preceding unsigned comment was added by David.Throop (talk • contribs) 13:52, 1 February 2007 (UTC).