Conjugated Linoleic Acid (CLA) ~ Good or Bad?

While I was looking at something unrelated (except that it was a fatty acid), the following popped up in my search:  Weight loss supplement - conjugated linoleic acid - shows nasty side effects.  Conjugated linoleic acid (CLA) first came to my attention, other than hearing about it as a supplement from time to time, during a discussion on trans fats and trans fat content of certain foods.  CLA is a trans fat, it's just not an unnatural nasty chemical we associate with the term these days.  It's found in meat of grassfed animals in particular, milk/dairy from same animals and eggs.   If you do a search on CLA and trans fat you'll turn up all manner of reports how it's the "good" or "healthy" trans fat.  In addition to some anti-cancer claims, it's also touted as the "belly busting" trans fat.  Sign me up!  

But, not so fast according to the article, which references two studies: (2007, nothing new here, just thought I'd pass this along as I hear buzz over CLA from time to time)

  • In mice, CLA supplementation caused rapid weight loss, but excessive hepatic fat accumulation and the mice became insulin resistant.
  • In rats, CLA supplementation did not cause whole body fat loss, but decreased hepatic fat content and the rats became more insulin sensitive.

“Many people take conjugated linoleic acid as a supplement in hopes of trimming body fat, and it seems to work,” Belury said. “But we're not sure what else it does to the body. Studying conjugated linoleic acid's effects in two different animal models may help us to better understand any additional effects in humans.
“It seems that these mice and rats represent a continuum of possible side effects induced by conjugated linoleic acid,” she continued. “The question is, are humans more like mice or rats? We're probably somewhere in between.”
Leaving aside whether rats or mice or neither is a good animal model to predict the human effects of CLA, one thing these two studies demonstrated was that hepatic fat accumulation/loss and body fat accumulation/loss are not always in the same direction.  By that I mean we see both hepatic fat accumulation with rapid weight loss, and hepatic fat loss despite no weight loss.  (Not sure if hepatic fat loss in the context of weight gain is possible though, that seems unlikely).  

Speaking of the mouse, however, the low carbers intent on championing some metabolic advantage that allows them to eat thousands of calories more and lose weight like no tomorrow love this rodent.  Remember Mighty Metabolism Mouse?   I've also blogged on Hepatic steatosis, inflammation, and ER stress in mice maintained long term on a very low-carbohydrate ketogenic diet.  The first study is legendary in low carb circles as the mice eat just as much and either don't gain as much weight or lose weight.  But this metabolism comes at the cost of profound liver damage.  

So let me be clear that there's much more on this topic that I'm not really all that interested in pursuing at this time(too much I'm more interested in at the moment), but here's one human study that caught my eye:  Conjugated Linoleic Acid Impairs Endothelial Function.
To determine the effect of dietary supplementation with conjugated linoleic acid (CLA) on body mass index (BMI), body fat distribution, endothelial function, and markers of cardiovascular risk.
Methods and Results
Forty healthy volunteers with BMI >27 kg/m2 were randomized to receive a CLA isomeric mixture or olive oil in a 12-week double-blind study. Subcutaneous body fat and abdominal/hepatic fat content were assessed using skin-fold thicknesses and computed tomography scanning, respectively. Endothelial function was assessed by brachial artery flow-mediated dilatation (FMD). Plasma isoprostanes were measured as an index of oxidative stress. CLA supplementation did not result in a significant change in BMI index or total body fat. There was a significant decrease in limb (−7.8 mm, P<0.001), but not torso skin-fold thicknesses or abdominal or liver fat content. Brachial artery FMD declined (−1.3%, P=0.013), and plasma F2-isoprostanes increased (+91pg/mL, P=0.042).
A CLA isomeric mixture had at most modest effects on adiposity and worsened endothelial function. On the basis of these results, the use of the isomeric mixture of CLA as an aid to weight loss cannot be recommended.
The F2-isoprostanes are "a lipid peroxidation product generally considered to be a marker of increased oxidative stress"  

Where I'd be concerned is that if CLA worked for me to lose weight like gangbusters, would that make me more mouse like and be counterproductive to health.  If it didn't work for weight loss per se, maybe it's doing a lot of good!  Quite a conundrum.


MM said…
I was trying to find some numbers on how much CLA is in butter and I found this study.

Conjugated Linoleic Acid–Enriched Butter Fat Alters Mammary Gland Morphogenesis and Reduces Cancer Risk in Rats

"Control butter and high CLA butter contained 5.1 and 41.0 mg CLA/g of fat, respectively."

In the human study Carbsane cites the volunteers were given 4.5 g CLA/day. "Subjects were randomly assigned to receive 4.5 g/d of CLA(isomeric mixture 60 calories/d)" (How 4.5 g of fat makes 60 calories I don't get, but whatever.)

So, if you were eating high CLA butter you'd have to eat about 10 grams of butter to get 4.5 g CLA. That's less than a tablespoon, so really not that much. However, with regular butter you'd have to eat closer to 100 grams, which is nearly a whole stick.

Another thing I thought was interesting, or maybe surprising (for me) is that the cows were able to produce high CLA milkfat by being fed sunflower oil. "Cows (n = 20) used to provide the high CLA butter were fed a similar diet with the addition of 5.3% sunflower oil."

I don't really have a comment about this. I'm just sharing, because I like to have some perspective on what the numbers mean in the real world.
MM said…
Oh crap I did my math wrong. I'm off by a factor of ten. So, you'd need to eat almost a whole stick of the high CLA, and then nearly 10 sticks of the regular butter. Sorry, I guess it's too early in the morning for my brain.
MM said…
I'm on Pacific time so it was not quite 6 AM for me. :) Anyway, it seems to me like even one stick of butter is quite a lot. I maybe could have eaten a stick in my bad old low carb days, but I definitely don't eat that much now.
Bixy said…
Isn't there a difference between the synthetic version and the real deal? I remember Chris Kresser doing a piece on the differences. Or maybe it was J Stanton.

Does this study describe which was used?
David Pier said…
There are many different CLA isomers and it is apparent that they have different effects. Supplementation with, or studies that use, isomers other than the commonly occurring in ruminant animal products, is highly dubious.
bentleyj74 said…
Sounds like the jury is out as per usual :)
Stephan Guyenet said…
Although the CLA isomers found in supplements are the same as those found in butter, butter contains a different proportion of isomers (and a greater variety-- there are 28 possible isomers and dairy contains a number of them). Supplements contain a high proportion of t10c12 CLA (usually 50-100%), which is the most active ingredient for fat loss in mice and humans. However, it also seems to be the most harmful in other ways. Dairy is predominantly c9t11 CLA and contains very little t10c12. But the overall concentrations in butter are low anyway, and probably not very biologically active if at all.
Woodey said…
I never could fully embrace the LC community's attitude towards calories. Common sense makes me question the idea that calories don't count, or as long as its non-insulin stimulating foods its ok to eat away. Another thing I've noticed on blogs from LC/paleo people is the mindset "Studies done by rats are not conclusive because they are not people and humans have a different system", then they turn around and point to a study done on rodents that supports their ideas. Can't have it both ways folks. Sorry Naughton I know you love to point out bad science when it doesn't endorse your point of view, but you have to use the same measuring stick on the data you like.

Bottom line is weight loss is very hard, its challenging, and down right painful at times. It takes a lot of determination and grit to lose a substantial amount of weight. There is no magic pill or magic rat that will lessen the amount of blood, sweat, and tears it will take to get rid of it. As badly as I want there to be, its just not gonna happen. Anyone telling people differently is selling something.

Like Belury said, “But we're not sure what else it does to the body". Same rule applies to these fad diets, short-term results should not be used to gauge long-term. I'd rather struggle with losing weight and have some extra pounds than take something that has a big unknown factor.
Unknown said…

Conjugated linoleic acid supplementation for 1 y reduces body fat
mass in healthy overweight humans

Long-term supplementation with CLA-FFA or CLA-triacylglycerol reduces BFM in healthy overweight adults

conclusion, aCLAmixture containing 80%trans-10, cis-12 and cis-9, trans-11 isomers, administered either in the triacylglycerol or FFA form to healthy overweight adults for 1 y, results in a significant decrease in BFM. Future studies are needed to address the role of CLA in CVD, diabetes, and oxidative stress.

Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans

In conclusion, when the body of evidence is considered as a whole, CLA does have a beneficial effect on human body composition. Although this effect is modest, it could be important if accumulated over time, especially in an environment where continuous, gradual weight gain is the norm in the adult population.
Unknown said…

Doing cardio is better than doing nothing. In the end, aerobic training does yet rarely produce those changes in body composition most "dieters" have in mind, when they embark on their daily jogging regimen and combine those with the latest and greatest diet fad they read about in magazines or on the Internet. If these people just added a few strength workouts to the equations, though, their bodies would begin to change; and what's even more exciting, according to a soon to be published study from the Pamukkale University in Denizli, Turkey, they will do that in the absence of any dietary changes and in exactly those problem areas, men and women usually hate the most about themselves: The trunk, for men, and the legs, for women
James Krieger said…
The data on CLA for fat loss in humans isn't very convincing. We're talking perhaps a a pound or two per year...certainly not worth the cost of supplementation.
ItsTheWooo said…
"non-insulin stimulating foods" don't exist. Eating itself stimulates insulin. Fat calories increase insulin. Protein requires a ton of insulin. Insulin moves nutrients.

The "LC community" consists of housewives, professional borderline ED dieters, elderly diabetics, et al. Don't be surprised when some of these people sometimes say medically and scientifically irrational things like "non insulin stimulating foods can't make you gain any weight".

Also the weight reduced physical condition is quite a different story than gaining new max body fat. Jimmy moore easily regaining body fat on ad lib fat requires trivial insulin easily produced by his high calorie ketogenic diet. Will jimmy moore gain to a higher max weight with ketosis? No, it will be impossible, because the diet produces insufficient insulin for that. He will experience anorexia, nausea, food avoidance, will be adverse to eating enough nutrition, as is the case in all people who are overfed and try to gain weight without endocrinological disorder or assistance (e.g. megastrol).

The response to this subset of misinformed laypeople (i.e. with ridicule), or hand wave dismissing the insulin hypothesis in general, is disingenuous and lazy, and IMO prejudicial (Please can we keep scapegoating body fat as a visually unmistabkable scarlet letter of hedonism, weakness sloth and gluttony, pleeeease? Get this "insulin hypothesis" crap out of my brain, that fat lardass I saw waddling across the street is merely a bad person, lazy and gluttonous and out of control... I wouldn't hire them for a job and I wouldn't sit next to them on a bus. End discussion!)

If a child tells me he got a cold virus because he ate really cold ice cream, this has nothing to do with whether or not cold stress can (or can't) predispose to weakened immunity and makes no comments what so ever regarding infectious disease. It merely illustrates children say and think silly things.

Why are we so preoccupied with absurd myths of low carb dieters?

Why do we assume these absurd myths reflect at all the hypothesis of an insulin mediated pathophysiology of obesity? Why do we waste our time dissecting the beliefs of the ignorant? Anyone who tells you that you can eat 5000 calories of "insulin free food" and not gain weight needs to get a basic biological education stat, because "insulin free food" doesn't exist unless you are a type 1 diabetic and choose not to use your insulin, in which case, yes, all food is insulin free.

To be fair low carb diet pushers have promoted this myth in the past...but again, why do we BIASED focus on the myth and gimmicks of low carbers, but shrug our shoulders/blind eye turn to the non-low carb diet guru gimmick snake oil salesmen who say equally if not FAR MORE absurd things?

Why do I have to deal with hordes of people who believe emotions make them fat, for example, and I have to respect those absurd delusions, meanwhile I am expected to mock jimmy moore who is equally delusional when he believes god made hamburgers and cream and butter and they magically protect him from obesity no matter how much he consumes?
CarbSane said…
" overall concentrations in butter are low anyway, and probably not very biologically active if at all."

So too with resveratrol, etc.etc. and the bad "addictive" stuff too like opioids in wheat. Generally concentrations in foods are too low to have any effect at all.
CarbSane said…
Wooo, it's not the members of the LC community. It's the so-called experts like Taubes, Eades, the late Atkins, Volek, Phinney, Westman, Davis, etc.etc.etc. There's a new wave on this old insulin bandwagon. Endocrinology cannot explain the obesity epidemic and low carb is no more effective at producing permanent weight loss than other approaches. As for Jimmy Moore, the only think I mock about him is his absurd practice of adding a ton of butter to his meals and inability to see how when he exercised and didn't "up the fat" on everything, he was able to maintain his weight. Mock people all you want on your blog. BTW, Jimmy is not hyperinsulinemic, or he wasn't when in 2008 he first started losing his grip on his weight, three years after losing it.

@Woodey: This was the reason I started looking into this stuff. What else does it do to the body besides weight loss. If LC really alters the partitioning of fuel and fats, is that beneficial/harmful/indifferent compared to a more balanced diet. And why do we have to compare that to a whole grain based MyPlate/Pyramid diet all the time. That's not what the SAD is anyway.
Galina L. said…
At the beginning of my LCarbing the only thing I had to count was the carb content of my diet, and such experience is very common, here is the attitude toward calories. However, after I lost my initial 20 - 22 lb, I had to pay more attention on the amount of food I ate and how often I ate. Such diet helped me to stop being a food addict, and now I can comfortably eat less and don't feel that I suffer . I am being lucky not to have extremely big amounts of lb to loose. I agree with you - weight loss is hard and painful.
I have been on and off diets all my adult life, I can tell, that keeping carbs to a minimum switched something in my body what trying to follow ELMM approach didn't. I am in a better metabolic state and control my appetite better with any food now. There are many LCarbers who can start eating more starches and fruits without regaining weight after initial very LC period. So ,there is some ground for disregarding calories, but just a few are so lucky to count on that.
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