CLA quality
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There could be differences, but I think the main point and something I just recently learned myself is that CLA supplementation isn't the best way to go about getting EFAs or their benefits. Odd but apparently true. There was a recent thread about this, search for EFA and see what pops up.[b said:
While CLA is a metabolite of linoleic acid (one of the essential fatty acids) it has different metabolic fates than that of LA, ALA or any of hte longer chain derivatives.
LA has 2 double bonds, both cis config, CLA actually has a trans and a cis double bond, hence the conjugate descriptor.
LA and CLA are omega6 fatty acids, which are different to any omega3 fatty acids such as ALA, EPA and DHA
LA has 2 double bonds, both cis config, CLA actually has a trans and a cis double bond, hence the conjugate descriptor.
LA and CLA are omega6 fatty acids, which are different to any omega3 fatty acids such as ALA, EPA and DHA
[b said:
Conjugated linoleic acid and obesity control: efficacy and mechanisms.
Wang YW, Jones PJ.
School of Dietetics and Human Nutrition, Macdonald Campus, McGill University, Ste-Anne-de-Bellevue, Quebec, Canada.
Obesity is associated with high blood cholesterol and high risk for developing diabetes and cardiovascular disease. Therefore, management of body weight and obesity are increasingly considered as an important approach to maintaining healthy cholesterol profiles and reducing cardiovascular risk. The present review addresses the effects of conjugated linoleic acid (CLA) on fat deposition, body weight and composition, safety, as well as mechanisms involved in animals and humans. Animal studies have shown promising effects of CLA on body weight and fat deposition. The majority of the animal studies have been conducted using CLA mixtures that contained approximately equal amounts of trans-10, cis-12 (t10c12) and cis-9, trans-11 (c9t11) isomers. Results of a few studies in mice fed CLA mixtures with different ratios of c9t11 and t10c12 isomers have indicated that the t10c12 isomer CLA may be the active form of CLA affecting weight gain and fat deposition. Inductions of leptin reduction and insulin resistance are the adverse effects of CLA observed in only mice. In pigs, the effects of CLA on weight gain and fat deposition are inconsistent, and no adverse effects of CLA have been reported. A number of human studies suggest that CLA supplementation has no effect on body weight and insulin sensitivity. Although it is suggested that the t10c12 CLA is the antiadipogenic isomer of CLA in humans, the effects of CLA on fat deposition are marginal and more equivocal as compared to results observed in animal studies. Mechanisms through which CLA reduces body weight and fat deposition remain to be fully understood. Proposed antiobesity mechanisms of CLA include decreased energy/food intake and increased energy expenditure, decreased preadipocyte differentiation and proliferation, decreased lipogenesis, and increased lipolysis and fat oxidation. In summary, CLA reduces weight gain and fat deposition in rodents, while produces less significant and inconsistent effects on body weight and composition in pigs and humans. New studies are required to examine isomer-specific effects and mechanisms of CLA in animals and humans using purified individual CLA isomers.
Effect of conjugated linoleic acid on body composition and plasma lipids in humans: an overview of the literature.
Terpstra AH.
Department of Laboratory Animal Science, Faculty of Veterinary Medicine, Utrecht University, Utrecht, Netherlands. a.h.m.terpstra@las.vet.uu.nl
Studies in mice have indicated that feeding diets containing 0.5-1% conjugated linoleic acid (CLA) considerably reduces body fat. These findings have attracted much interest because of the potential use of CLA as a tool to promote weight loss in humans. Several CLA studies in humans have now been published, and the objective of the present review was to give an overview of these experiments. Most of the studies were done in free-living subjects and were not strictly controlled for nutrient and energy intakes. None of the studies found a significant reduction in body weight, and only 2 studies showed a significant but relatively small body fat-lowering effect. Some studies suggested that CLA may have a tendency to increase lean body mass. Furthermore, there are indications from animal studies that CLA may have effects on plasma lipids. However, only one study in humans showed a significant HDL-cholesterol-lowering effect of CLA; in all the other studies, there were no significant effects on plasma total, LDL-, and HDL-cholesterol concentrations or on plasma triacylglycerol concentrations. Thus, the results of the studies in humans indicate that the effect of CLA on body fat is considerably less than that anticipated from mice studies and that CLA has no major effect on plasma lipids.
Conjugated linoleic acid in humans: regulation of adiposity and insulin sensitivity.
Brown JM, McIntosh MK.
Department of Nutrition, University of North Carolina at Greensboro, Greensboro, NC 27402-6170, USA.
Conjugated linoleic acid (CLA) isomers, a group of positional and geometric isomers of linoleic acid [18:2(n-6)], have been studied extensively due to their ability to modulate cancer, atherosclerosis, obesity, immune function and diabetes in a variety of experimental models. The purpose of this review was to examine CLA's isomer-specific regulation of adiposity and insulin sensitivity in humans and in cultures of human adipocytes. It has been clearly demonstrated that specific CLA isomers or a crude mixture of CLA isomers prevent the development of obesity in certain rodent and pig models. This has been attributed mainly to trans-10, cis-12 CLA, both in vivo and in vitro. However, CLA's ability to modulate human obesity remains controversial because data from clinical trials using mixed isomers are conflicting. In support of some studies in humans, our group demonstrated that trans-10, cis-12 CLA prevents triglyceride (TG) accumulation in primary cultures of differentiating human preadipocytes. In contrast, cis-9, trans-11 CLA increases TG content. Closer examination has revealed that CLA's antiadipogenic actions are due, at least in part, to regulation of glucose and fatty acid uptake and metabolism. This review presents our current understanding of potential isomer-specific mechanisms by which CLA reduces human adiposity and insulin sensitivity.
Efficacy and safety of dietary supplements containing CLA for the treatment of obesity: evidence from animal and human studies.
Larsen TM, Toubro S, Astrup A.
Department of Human Nutrition, Center for Advanced Food Studies, The Royal Veterinary and Agricultural University, DK-1958 Frederiksberg C, Denmark. tml@kvl.dk
Dietary supplements containing conjugated linoleic acid (CLA) are widely promoted as weight loss agents available over the counter and via the Internet. In this review, we evaluate the efficacy and safety of CLA supplementation based on peer-reviewed published results from randomized, placebo-controlled, human intervention trials lasting more than 4 weeks. We also review findings from experimental studies in animals and studies performed in vitro. CLA appears to produce loss of fat mass and increase of lean tissue mass in rodents, but the results from 13 randomized, controlled, short-term (<6 months) trials in humans find little evidence to support that CLA reduces body weight or promotes repartitioning of body fat and fat-free mass in man. However, there is increasing evidence from mice and human studies that the CLA isomer trans-10, cis-12 may produce liver hypertrophy and insulin resistance via a redistribution of fat deposition that resembles lipodystrophy. CLA also decreases the fat content of both human and bovine milk. In conclusion, although CLA appears to attenuate increases in body weight and body fat in several animal models, CLA isomers sold as dietary supplements are not effective as weight loss agents in humans and may actually have adverse effects on human health.
Modulation of body composition and immune cell functions by conjugated linoleic acid in humans and animal models: benefits vs. risks.
Kelley DS, Erickson KL.
Western Human Nutrition Research Center, ARS, USDA, Department of Nutrition, University of California Davis, Davis, California 95616, USA. dkelley@whnrc.usda.gov
We have reviewed the published literature regarding the effects of CLA on body composition and immune cell functions in humans and in animal models. Results from studies in mice, hamsters, rats, and pigs generally support the notion that CLA reduced depot fat in the normal or lean strains. However, in obese rats, it increased body fat or decreased it less than in the corresponding lean controls. These studies also indicate that t10,c12-CLA was the isomer that reduced adipose fat; however, it also increased the fat content of several other tissues and increased circulating insulin and the saturated FA content of adipose tissue and muscle. Four of the eight published human studies found small but significant reductions in body fat with CLA supplementation; however, the reductions were smaller than the prediction errors for the methods used. The other four human studies found no change in body fat with CLA supplementation. These studies also report that CLA supplementation increased the risk factors for diabetes and cardiovascular disease including increased blood glucose, insulin, insulin resistance, VLDL, C-reactive protein, lipid peroxidation, and decreased HDL. Most studies regarding the effects of CLA on immune cell functions have been conducted with a mixture of isomers, and the results have been variable. One study conducted in mice with the purified c9,t11-CLA and t10,c12-CLA isomers indicated that the two isomers have similar effects on immune cell functions. Some of the reasons for the discrepancies between the effects of CLA in published reports are discussed. Although significant benefit to humans from CLA supplementation is questionable, it may create several health risks in both humans and animals. On the basis of the published data, CLA supplementation of adult human diets to improve body composition or enhance immune functions cannot be recommended at this time.
This is from a paper on one of the origonal CLA proponents.
http://www.ajcn.org/cgi/content/full/79/6/1132S
The findings to date provide insight for the design of human clinical trials. First, it is important to emphasize that in many animal models dietary CLA induces substantial reductions in body fat without substantially reducing body weight. For example, male or female weanling ICR mice fed diet supplemented with 0.5% CLA (composed approximately of equal mixture of c9,t11- and t10,c12-isomers) for 4 wk exhibited, respectively, 57% or 60% reductions in body fat relative to controls, whereas there were no significant differences in body weights relative to controls (24).
Second, in most animal models the reduction in body fat appears to be due mostly to reductions in body fat accretion, not reductions in body fat that had already accumulated before the initiation of the experiment. In fact mice are the only species that have clearly been shown to lose accumulated body fat when fed diet supplemented with t10,c12-CLA (4). Researchers speculated that this result could occur because mice may depend more than larger species on fat combustion for energy and, hence, are more sensitive to CLA-induced reductions in fat storage in adipocytes. Finally, there are considerable species differences with regard to reductions in body fat accretion in response to dietary CLA (30). Mice are the most sensitive, followed in order by hamsters and rats. Direct comparisons with pigs versus rodents have not been performed, but it would appear that pigs are likely to be intermediate, ie, more like hamsters than mice or rats in this regard (31).
Most of the published human clinical trials to date were designed to test the hypothesis that CLA ingestion will reduce accumulated body fat in adult humans (32). In general the protocols involved giving encapsulated CLA as a free fatty acid at an amount of about 3 g/d, with the highest intake in one study being 7.2 g/d (32). The results of those trials are mixed, but in general when the highest-quality commercially available grades of CLA were used, it was indicated there was significant body fat mass reduction relative to placebo controls (32). It is also indicated that CLA could prove to be most effective in reducing fat mass and increasing lean mass when combined with enhanced physical activity. However, CLA intake was not associated with significant reductions in body weight, which is also consistent with animal studies (4,
Kamphuis et al (33, 34) approached the issue differently, designing a protocol to test whether CLA could reduce the regain of body fat or body weight in overweight adults who were first subjected to a very-low-calorie weight loss diet. Subjects were given the very-low-calorie diet for 3 wk followed by a 13-wk intervention period during which subjects ate ad libitum but were given CLA (1.8 or 3.6 g) or placebo each day. Subjects taking CLA (either dose level) exhibited significantly greater regain of fat-free mass relative to control subjects, and the increased fat-free mass in the subjects ingesting CLA was reflected in significantly enhanced resting metabolic rate. Interestingly, measures of appetite (hunger, satiety, and fullness) were also favorably, dose-independently affected by CLA ingestion. However, as one might predict, the regain of body weight per se was not reduced by CLA ingestion. Blood lipids, glucose, and insulin were not affected by CLA ingestion.
The findings of Kamphuis et al (33, 34) support the conclusion that CLA might be most effective in controlling body fat accretion in anabolic humans, rather than reducing accumulated body fat per se.
All right, sir. I'll see your studies and raise you one. The following is from the Bryan.
"CLA does work in humans. Here are some references.
1. Jiang J, Wolk A, Vessby B. Relation between the intake of milk fat and
the occurrence of conjugated linoleic acid in human adipose tissue. Am J Clin Nutr. 1999 Jul;70(1):21-7.
2. Berven, G., Bye, A. & Hals, O. et al. (2000) Safety of conjugated
linoleic acid (CLA) in overweight or obese human volunteers. Eur. J. Lipid
Sci. Technol. 102:455-462.
3. Blankson, H., Stakkestad, J. A., Fagertun, H., Thom, E., Wadstein, J. &
Gudmundsen, O. (2000) Conjugated linoleic acid reduces body fat mass in overweight and obese humans. J. Nutr. 130:2943-2948.
4. Smedman, A. & Vessby, B. (2001) Conjugated linoleic acid supplementation in humans-metabolic effects. Lipids 36:773-781.
5. Kamphuis MM, Lejeune MP, Saris WH, Westerterp-Plantenga MS. The effect of conjugated linoleic acid supplementation after weight loss on body weight regain, body composition, and resting metabolic rate in overweight subjects. Int J Obes Relat Metab Disord. 2003 Jul;27(7):840-7.
6. Gaullier, J. M., Halse, J., Høye, K., Kristiansen, K., Fagertun, H., Vik,
H. & Gudmundsen, O. (2004) Conjugated linoleic acid (CLA) supplementation for one year reduces body fat mass in healthy, overweight humans. Am. J. Clin. Nutr. 79:1118-1125
7. Gaullier JM, Halse J, Hoye K, Kristiansen K, Fagertun H, Vik H,
Gudmundsen O. Supplementation with conjugated linoleic acid for 24 months is well tolerated by and reduces body fat mass in healthy, overweight humans. J Nutr. 2005 Apr;135(4):778-84.
I've attached a graphic of the mechanism of action of CLA.
The question often arises about why rats seem to lose fat rapidly whereas in humans the effect is much more subdued. The primary reason that rats have a more dramatic metabolic response is due to a fixed relationship between metabolic rate (thermogenesis) and body surface area. Compared to humans, rodents respond metabolically (thermogenesis) approximately 7 times stronger to CLA. Can't find the reference off hand that discusses this but its out there somewhere. "
Only the Bryan would know about the metabolism of rats.
Anyway, perhaps its just a question of what one considers a potent effect. Certainly its not going to melt pounds off you, but ...
"CLA does work in humans. Here are some references.
1. Jiang J, Wolk A, Vessby B. Relation between the intake of milk fat and
the occurrence of conjugated linoleic acid in human adipose tissue. Am J Clin Nutr. 1999 Jul;70(1):21-7.
2. Berven, G., Bye, A. & Hals, O. et al. (2000) Safety of conjugated
linoleic acid (CLA) in overweight or obese human volunteers. Eur. J. Lipid
Sci. Technol. 102:455-462.
3. Blankson, H., Stakkestad, J. A., Fagertun, H., Thom, E., Wadstein, J. &
Gudmundsen, O. (2000) Conjugated linoleic acid reduces body fat mass in overweight and obese humans. J. Nutr. 130:2943-2948.
4. Smedman, A. & Vessby, B. (2001) Conjugated linoleic acid supplementation in humans-metabolic effects. Lipids 36:773-781.
5. Kamphuis MM, Lejeune MP, Saris WH, Westerterp-Plantenga MS. The effect of conjugated linoleic acid supplementation after weight loss on body weight regain, body composition, and resting metabolic rate in overweight subjects. Int J Obes Relat Metab Disord. 2003 Jul;27(7):840-7.
6. Gaullier, J. M., Halse, J., Høye, K., Kristiansen, K., Fagertun, H., Vik,
H. & Gudmundsen, O. (2004) Conjugated linoleic acid (CLA) supplementation for one year reduces body fat mass in healthy, overweight humans. Am. J. Clin. Nutr. 79:1118-1125
7. Gaullier JM, Halse J, Hoye K, Kristiansen K, Fagertun H, Vik H,
Gudmundsen O. Supplementation with conjugated linoleic acid for 24 months is well tolerated by and reduces body fat mass in healthy, overweight humans. J Nutr. 2005 Apr;135(4):778-84.
I've attached a graphic of the mechanism of action of CLA.
The question often arises about why rats seem to lose fat rapidly whereas in humans the effect is much more subdued. The primary reason that rats have a more dramatic metabolic response is due to a fixed relationship between metabolic rate (thermogenesis) and body surface area. Compared to humans, rodents respond metabolically (thermogenesis) approximately 7 times stronger to CLA. Can't find the reference off hand that discusses this but its out there somewhere.
"Only the Bryan would know about the metabolism of rats.
Anyway, perhaps its just a question of what one considers a potent effect. Certainly its not going to melt pounds off you, but ...
I
imported_dkm1987
Guest
This one has always befuddled me, they make the statement that LBM and FM changes weren't significant but reviewing their table it clearly shows that the vast percentage of the studies had positive effects in both weight lost and FFM gain. Granted some of the numbers over control were small but for those who are obese any positive is helpful IMHO. I guess it comes down to efficacy versus expense.[b said:
In other words, if you can get it cheap go for it.
Awesome threads like these always seem to get me all verklempt.
Here is a graphic of CLA's proposed mechanisms.
Ok, now talk amongst yourselves.
Here is a graphic of CLA's proposed mechanisms.
Ok, now talk amongst yourselves.
you will also note that I never said it doesnt work[/quote][b said:
1. Jiang J, Wolk A, Vessby B. Relation between the intake of milk fat and
the occurrence of conjugated linoleic acid in human adipose tissue. Am J Clin Nutr. 1999 Jul;70(1):21-7.[/quote]
hmm
So CLA from dairy shows up in adipose
wonder what type of company I work for...
no significant difference in bodyweight or BMI??[b said:
a change. Why did they not measure caloric intake... nice for intention to treat, but its a bit odd.[b said:
They are interesting (as most are commented in the reviews mentioned above), but grabbing the research that shows positive effects, without the work that shows nil effect creates an uneven picture.[b said:
when combining the work it gets difficult. They didnt perform a meta analysis but 4/12 with a significant response (figure one) means that its probably unlikely to show a significant effect when combined. Hence, he said it wasnt significant. OR at least thats how I read it[b said:
and the difference between rat and human is more than just thermogenic response.