Conjugated Linoleic Acids: What's the Difference Between cis-9,11 and trans-10,12 CLA and Should We Label Them as "Transfats"? Plus: What Makes CLA Potentially Harmful?

If Hayden Panettiere drinks it dairy can't be bad - despite (or because?) CLA, right? Well, what if I told you that Mrs. Panettiere was advertising milk in the "Got Milk" campaign despite being lactose intolerant?

As a SuppVersity veteran you will be familiar with the idea that trans-10, trans-12 conjugated linoleic acid is the "fat burning" CLA isomer, while 9 cis,11 trans linoleic acid appears to blunt some of the pro-inflammatory actions of its cousin and has been shown to have specific physiological effects on it's own (e.g. increased bone health, cf. Platt. 2009; anti-cancer, cf. Corl. 2003).

As I already mentioned, this is probably nothing new for you, if you make sure to get your daily dose of SuppVersity wisdom everyday. What you may however not be aware of is the fact that researchers like Ye Wang and Spencer D. Proctor are - despite the never-ending hoopla around potential weight loss effects of CLA - still contemplating, whether CLA could not pose a major health threat to all or at least certain subgroups of the population and whether this should or shouldn't be reason enough to change the current food labeling practices.

Do we have to label CLA as "transfat"?

From a technical perspective the above question is obsolete. CLAs are transfats and would thus (technically, again) have to be labeled as such on the product label. From a health perspective, however, things do in fact look different. Due to the fact that the aforementioned ruminant (=naturally produced in the stomach(s) of ruminents) trans-fats have been associated with health benefits (Gebauer. 2011), we could effectively risk to scare consumers away from healthy foods if they were listed as part of the "transfat" category on the product labels.

What's actually the reason that one the same CLA isomer that will have you lose body fat will also "inflame" you? Due to the fact that most of the research on "fat loss supplements" is conducted in sick, obese individuals, people tend to get the false impression that "fat burners" were anti-inflammatory and that anti-inflammatory agents would burn fat.

Effects of 10-trans,12 CLA on fatty acids & glucose metabolism and IL-6 gene expression in isolated fat cells in the petri dish (Hartwig. 2013)

Now, while it is correct that soothing inflammation will help the future Mr. Average Joe, who is going to be an obese (pre-)diabetic, lose weight, this has little to do with any active contribution to the oxidation of body fat. 10-trans,12 CLA, on the other hand, has been shown to block lipid storage, increase mitochondrial uncoupling (UCP-2), lower PPAR-alpha and ramp up the oxidation and release of fatty acids from the fat stores (Hartig. 2013). Unfortunately it will also block the uptake of glucose and increase the expression of the pro-inflammatory cytokine IL-6 in fat cells. So, if you took 10-trans,12 CLA at very high doses it will probably in fact keep you lean.

If you cannot handle the sudden increase in free fatty acids, pack the glucose into your liver and muscle glycogen stores and deal with the exuberant amount of inflammatory cytokines, however, it will only make you sick.

Currently, the trans-fat content on many food labels (and in legislative documents) does not include ruminant CLA isomers and Wang and Procter acknowledge that:

"As highlighted in a recent quantitative review of prospective cohort studies by Bendsen et al. dietary consumption of ruminanttrans-fat may be protective against total as well as fatal CHD events." (Wang. 2013)

The researchers do however point out that concerns about potential adverse effect on atherogenic cholesterol profiles from supplemental CLA are not unwarranted - at least if they are used by a group of persons - abdominally obese and/or insulin resistant men, for example (Riserus. 2002 a,b).

Australia and New Zealand suggest a re-evaluation

Accordingly, Australia and New Zealand (FSANZ) proposed to re-evaluate their perception regarding the exclusion of CLA from the TFA definition on nutrition labels.

If you re-evaluate something, you do not necessarily have to change them and if you go through the concise summary of results Wang and Procter present in their paper (see table 1 for an overview of the currently published meta-analyses, it does not appear necessary to question the current practice to label only industrually produced trans fats.

Table 1: Meta analysis with beneficial (green), neutral (grey) and potentially negative outcome (red); based on Wang & Proctor (2013)

As the authors point out, the inclusion of CLA in the total amount of transfats on the label would only drive people away from the consumption of whole food products. This is particularly true in view of the fact that the ill-health effects of "trans-fats" are something everyone will have heard about. The fact that these ill health effects are not to be expected from trans fats in dairy and other CLA containing whole foods, on the other hand, is still news to many costumers.

Moreover, how would you, me and everyone else who may well be aware that CLAs are not the bad guys and the "trans-fat" in grass fat butter is not going to hurt us know if the 3g of transfats in another product we buy are actually from the undisclosed amount of butter (and thus CLA) in it? It could likewise be that the producer added a little extra partially hydrogenated vegetable oil to cut the product costs and neither you nor me would know that.

Suggested read: "A Higher Intake of CLA and Vaccenic Acid from Dairy, Beef, Veal and Lamp Could Prevent Subtle Weight Gain" | read more

Only the obese have to be worried: Based on the currently available evidence the healthy and lean person (hopefully you) has absolutely no reason to avoid products with a "high" natural CLA content and thus both the pro- (trans-10,12) and (partly) anti-inflammatory (cis-9,11) form of CLA in them.

For obese and insulin resistant individuals things do however look somewhat different. A 2004 study by Risérus et al., for example, has been able to show that even the allegedly "harmless", 9 cis,11 trans linoleic acid can worsen both lipid peroxidation and insulin resistance in 25 abdominally obese men. (Risérus. 2004).

With 3g/day the dosage that was used in the Risérus study, the amount of CLA was yet much hither than the amount of CLA you can possibly ingest with nourishing foods such as butter, full-fat dairy, grass-fed beef (and beef in general, by the way). Instead of these you are thus better advised to avoid CLA supplements... but don't worry if you take another look at the data in table 1 you will have to concede that they are pretty much useless, anyway.

Reference:

• Corl BA, Barbano DM, Bauman DE, Ip C. cis-9, trans-11 CLA derived endogenously from trans-11 18:1 reduces cancer risk in rats. J Nutr. 2003 Sep;133(9):2893-900.
• Gebauer SK, Chardigny JM, Jakobsen MU, et al. Effects of ruminanttrans fatty acids on cardiovascular disease and cancer: a comprehensive review of epidemiological, clinical, and mechanistic studies.Adv Nutr. 2011; 2, 332 – 354.
• den Hartigh LJ, Han CY, Wang S, Omer M, Chait A. 10E,12Z-conjugated linoleic acid impairs adipocyte triglyceride storage by enhancing fatty acid oxidation, lipolysis, and mitochondrial reactive oxygen species. J Lipid Res. 2013 Nov;54(11):2964-2978. 
• Lenz TL & Hamilton WR. Supplemental products used for weight loss. J Am Pharm Assoc. 2004; 44,  59– 67, quiz 67– 58.
• Onakpoya IJ, Posadzki PP, Watson LK, Davies LA, Ernst E. The efficacy of long-term conjugated linoleic acid (CLA) supplementation on body composition in overweight and obese individuals: a systematic review and meta-analysis of randomized clinical trials. Eur J Nutr. 2012 Mar;51(2):127-34.
• Platt I, El-Sohemy A. Effects of 9cis,11trans and 10trans,12cis CLA on osteoclast formation and activity from human CD14+ monocytes. Lipids Health Dis. 2009 Apr 29;8:15.
• Risérus U, Arner P, Brismar K, Vessby B. Treatment with dietary trans10cis12 conjugated linoleic acid causes isomer-specific insulin resistance in obese men with the metabolic syndrome. Diabetes Care. 2002 Sep;25(9):1516-21.
• Risérus U, Basu S, Jovinge S, Fredrikson GN, Arnlöv J, Vessby B. Supplementation with conjugated linoleic acid causes isomer-dependent oxidative stress and elevated C-reactive protein: a potential link to fatty acid-induced insulin resistance. Circulation. 2002 Oct 8;106(15):1925-9
• Salas-Salvadó J, Márquez-Sandoval F, Bulló M. Conjugated linoleic acid intake in humans: a systematic review focusing on its effect on body composition, glucose, and lipid metabolism. Crit Rev Food Sci Nutr. 2006;46(6):479-88. Review.
• Schoeller DA, Watras AC, Whigham LD. A meta-analysis of the effects of conjugated linoleic acid on fat-free mass in humans. Appl Physiol Nutr Metab. 2009 Oct;34(5):975-8.
• Tricon S, Yaqoob P. Conjugated linoleic acid and human health: a critical evaluation of the evidence. Curr Opin Clin Nutr Metab Care. 2006 Mar;9(2):105-10. Review.
• Whigham LD, Watras AC, Schoeller DA. Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans. Am J Clin Nutr. 2007 May;85(5):1203-11.

CLA Destroys Body Fat & Increases Endurance! But at Which Costs? It Almost Triples Liver & Doubles Spleen Weight and Increases Blood Glucose & Cholesterol Levels!

Image 1 (Zhu. 2012): The allegedly leaner mouse on the left has a certain gene defect due to which it developed both lipodystrophy (fat loss) and diabetes early in life. Now guess what the mice on the 5% CLA diet developed after 6 weeks?

It is quite funny how the same people who are terrified by the thought that creatine (suggested read "The Pharmacokinetics of Creatine") could damag their kidneys cast caution to the wind, when it comes to magical fat loss pills. "CLA does help fat loss? How can I get more of it?" While the non-existence of conclusive evidence that conjugated linoleic acid does even work in human and the presence of at least 28 isomers of linoleic acid, which are mainly found in the meat and dairy products from ruminants (Banni. 2002) and of which only one seems to "work" is one thing, the ignorance people display for the potential negative side effects high doses (so high that they would maybe help you burn body fat) can have on liver function, glucose metabolism, oxidative stresses and more (cf. Dilzer. 2012) is potentially hazardous.

"CLA is from grass-fed cows so it must be good, right!?"

Sometimes I get the feeling the above statement conveys an accurate representation of the counter-productive black-and-white thinking that is so prevalent among some of the health nuts on the Internet, these days. And in fact, if you take a cursory look at the heavily quoted studies on the effects of CLA on all sort of things ranging from its general antioxidative effects (Reynolds. 2010), over the profane reduction of unaesthetic body fat (in rodents, cf. Wang. 2004) to its purported anti-cancer effects (Tanaka. 2011) it does conjugated linoleic acid is probably second only to vitamin D and fish oil in terms of its contemporary idolatry and, if we regard the fat loss effects in isolation and focus solely on a recent study by scientists from the Department of Food Science at the University of Massachusetts rightly, so!

After all, the results Kim et al. present in the latest issue of Lipids are unquestionably impressive: 70% reduced body fat levels in normal-weight rodents with nothing but 0.5% CLA (as trans-10,cis-12 CLA) in regular rodent chow within 6 weeks!? You can hardly argue that this isn't an impressive result.

Figure 1: Tissue weights (left, large), muscle and liver glycogen content (left small, inset) after and body weight (right, top) as well as food intake (right, bottom) in the course of the 6-week study period (adapted from Kim. 2012)

Aside from the only at first sight remarkable -77% reduction in body fat in the presence of an almost 30% increased food intake (!), the data in figure 1 does yet also confirm other, outcomes we already know from previous studies:

1. only the trans-10,cis-12, but not the cis-9,trans-11 CLA isomer will yield the desired anti-obesity effects
2. instead of healthy weight loss in obese or at least overweight animals, CLA induces what in every other context would be called full-blown lipodystrophy (=pathologic loss of body fat, cf. image 1 and Jaudszus. 2010) in the lean perfectly healthy 129Sv/J mice in the study at hand - and that in the presence of ~30% increased food intake (see figure 1, bottom right)
3. worrisome increases in liver and spleen weight, the latter of which exceed the +76% increase in hepatic glycogen storage capacity by more than a factor 2x (!)

Figure 2: Serum levels of triglycerides, glucose, total cholesterol, non-esterified fatty acids, lactate and blood urea nitrogen in CLA supplemented expressed relative to non-supplemented control (large) and additional figure showing expressions of selected genes from skeletal muscle (based on Kim. 2012)

Let's be honest, if you observed similar increases in food consumption that are accompanied not by gains, but by profound reductions in body fat in your dog, cat, bird, pig or whatever pet you may have, you would interpret that as a clearcut sign that something is awfully wrong with your loved one and seek medical advice right away - correct?

A brief note on the figures in this paragraph: While the examples are hypothetical, the figures I came up with reflect the reductions in body fat and increases in liver weight, glucose and total cholesterol you see in figure 2.

So, why on earth would you even remotely consider going to your local GNC then to get yourself a family pack of CLA cabs in order to get rid of the flab that's still covering your abs? Are you keen on taking yourself to the Dr. after 6-weeks, when you are down from 15% body fat to 4.5% (=70% reduction) and you formerly flabby belly is now bulging because your liver, which does now weigh 4kg instead of the regular 1.5kg, is oozing out from under your ribcage? If that's what you are looking for, you probably won't be worried if your blood glucose shot up from 90 to 112pts and your Dr. is about to prescribe an (in your case particularly unnecessary) statin to sooth your ~50% increased cholesterol levels, either!? You are lean, now! And as Kim et al. euphorically point out your endurance may even increase by 70%(!) while there is still some muscle or liver glycogen or body fat left to fuel the PPAR-gamma driven fat burning wreck you have become...

Image 2: One of the best CLA supplements there is - ok, it's a proprietary blend with small amount of omega-3, omega-6 and important and increasingly scarce vitamins as vitamin A and vitamin K, but you can trust in the divine wisdom of its inventor - mother nature ;-)

Implications: If all the irony has not yet allured you from the idea that you'd better be lean and sick, than somewhat chubby and healthy, you may be disappointed to hear that the human equivalent dose of the trans-10,cis-12 CLA (remember no other form will do this black magic!) is roughly 30g/day and thus probably more expensive than liposuction ;-)

This dosage issue does yet bring us back to where we came from: Grass-fed cows!  After all, it is not only unrealistic, but simply impossible to get this amount of CLA (let alone only t-10,c-12) from your diet- regardless of how much meat and dairy from grass-fed cattle you consume! And based on the the results of the study at hand, you could even argue that nature has rendered that impossible for a good reason, your protection.

So don't pretend you are smarter than nature and stick to your Kerrygold golden grass-fed Irish butter - not so much for the CLA content, though, but for the whole package of synergistically acting power-nutrients nature has put into her original "fat supplement" ;-)

References:

• Banni S. Conjugated linoleic acid metabolism. Curr Opin Lipidol. 2002 Jun;13(3):261-6.
• Dilzer A, Park Y. Implication of conjugated linoleic acid (CLA) in human health. Crit Rev Food Sci Nutr. 2012;52(6):488-513.
• Jaudszus A, Moeckel P, Hamelmann E, Jahreis G. Trans-10,cis-12-CLA-caused lipodystrophy is associated with profound changes of fatty acid profiles of liver, white adipose tissue and erythrocytes in mice: possible link to tissue-specific alterations of fatty acid desaturation. Ann Nutr Metab. 2010;57(2):103-11.
• Kim JH, Kim J, Park Y. trans-10,cis-12 Conjugated Linoleic Acid Enhances Endurance Capacity by Increasing Fatty Acid Oxidation and Reducing Glycogen Utilization in Mice. Lipids. 2012 Jul 11.
• Reynolds CM, Roche HM. Conjugated linoleic acid and inflammatory cell signalling. Prostaglandins Leukot Essent Fatty Acids. 2010 Apr-Jun;82(4-6):199-204. Epub 2010 Mar 7.
• Tanaka T, Hosokawa M, Yasui Y, Ishigamori R, Miyashita K. Cancer chemopreventive ability of conjugated linolenic acids. Int J Mol Sci. 2011;12(11):7495-509. Epub 2011 Nov 2. 
• Wang YW, Jones PJ. Conjugated linoleic acid and obesity control: efficacy and mechanisms. Int J Obes Relat Metab Disord. 2004 Aug;28(8):941-55. Review.
• Zhu. Ncb5or in Fatty Acid Desaturation and Metabolic Diseases. Zhu Diabetes Research Group. University of Kansas School of Health Professionals. < http://www.alliedhealth.kumc.edu/school/research/zhu/more_info.html > retrieved July 22, 2012